Mini Van Overheating

Water pump and thermostat are the first to check.

Best way to check thermostat, (I even check new ones before installing), is to place it in a pot of water with a candy thermometer, bring to boil, and make sure it opens at the correct temperature.

I agree with Lyn,

It sounds like an airlock in the system such that the sensor is not seeing the true water temperature, but is sitting in an air pocket ..... that was my first thought, however I can also think of another possibility:

If your radiator cap has lost its ability to hold pressure, then it will also boil with the temp gauge reading normal temp ...... remember that the normal temp is often above the boiling point of your coolant at atmospheric pressure - the radiator cap has a pressure rating - ie pressure in the radiator increases with temp and prevents the coolant boiling. If the radiator cap is not holding the pressure it will then boil.

You may only need a new radiator cap.....

Could be a failed water pump or thermostat. Typically, the fluid in the radiator does not get hot, only the fluid in the engine water jackets, so I would not suspect that to be the issue.

Does the heater work? If not that would indicate a flow issue. If it does work, then the issue is probably the radiator not cooling the fluid.

For that failure mode you should first check the radiator fan. Most are electric and this is the most common cause of failure for the cooling system in cars.

The easiest test for the fan is to run the AC and see if the fans engage. If they do not you can do a continuity test of the fan at the connector or even supply 12 VDC to that connection. Chances are it is the fan itself.

If the fan tests okay but refuses to engage, reseat the relays and fuses associated with the cooling system. Failing a bad fuse you may have a bad relay.

Typically, the fluid in the radiator does not get hot, only the fluid in the engine water jackets, so I would not suspect that to be the issue.

What's up AH? Just waking up?

Of course the fluid in the radiator gets hot. Hot enough to scald anyone that removes the radiator cap on a hot engine. NOT A GOOD IDEA!

However, if the fluid flow stops (i.e., the water pump arrests), then you will not get much heat out of the radiator, will you?

From the OP: The temp gauge reads normal,but when driving the radiator boils over and and the temp gauge falls to 50% of center

You're back peddling. Your comment that radiator fluid typically does not get hot was just wrong...................at least in this context. I see the angle that you're coming from, but it's not real clear. Especially to someone not familiar with automotive work.

From my post #3, "Could be a failed water pump or thermostat. Typically, the fluid in the radiator does not get hot..."

My fault. I can see that I did not strongly tie the two sentences together. The meaning was that if the water pump fails (and no circulation takes place), then the fluid in the radiator will not get hot (or very hot). The fluid in the engine block will get hot and it may even boil, which could back flow into the radiator if left unchecked.

However, the original post stated that the radiator does get hot. So, my first thought would be to check that the radiator fans are working. This is non invasive and nothing need be dismantled. It is also the most common cause of overheating.

I figured out what you were getting at after I posted. The way it was written was a little confusing.

I could have done better... :-/

Weeeeeeeeeelllllllllllllll...................

Not really confusing, considering the author.

The casual reader may have been confused, but with no new paragraph, the subject would not have changed.

You will note that with every new subject, comes a new paragraph, at least with this particular author, AH.

Editor lyn

Yeah, yeah. There was also the early morning, coffee driven excitement of being able to snap AH.

There really isn't a good way to be a casual car fixer. Admittedly, I'm lost on this new computer stuff in cars, but the best way for someone that wants to work on their own car, is do some reading on the IC engine, how it works, buy a reputable manual, (Haynes works for me, although the factory manuals are best), and read it, follow the troubleshooting procedures, etc. It takes time to become familiar with the workings of an automobile and be able to fix it right.

That's what I did about 30 years ago, and today, if it's not computer related, I can usually fix it..........................within reason. I've never torn apart a transmission either.

"the fan came on" in the OP. It is not the fan operation.

Check the lower radiator hose. Maybe it is collapsing at higher engine rpm's. That'll ruin your day for sure.

Give it a squeeze (lower rad hose). If it collapses, then it may do it also when engine is revving, due to water pump suction. It may need a spring (stainless) inside to hold it open. However if no spring fitted originally, then this is not the main problem.

Re temp gauge, check all your connections and earths. But they won't cause it to boil. Is radiator clean? Flushed? Then it may be the water pump -

Well first thing, after searching the web on this, I would say check the brakes!! A lot of problems with brakes wearing out prematurely....

1

• See if the water pump is leaking. Your water pump pushes coolant through the engine, radiator and heater core. A slight smell of antifreeze or spots of it under your Town & Country when parked for a short time indicate a worn out water pump.
• 2Check the hoses for cracks, collapses, leaks or dryness. This includes upper and lower radiator hoses, heater and bypass hoses and manifold coolant hoses. Your upper hoses for instance, measure about 2 inches wide and carry coolant between the radiator and engine. Damaged hoses lead to cooling system problems.
• 3Look at the coolant amount. Overheating can result from low antifreeze levels, so add it to the coolant tank reservoir. Use a 50/50 mixture of Mopar Antifreeze/Coolant 5 year, 100,000 Mile Formula HOAT (Hybrid Organic Additive Technology) and water. Use this mix in the 3.3L and 3.8L engines.
• 4Drain and flush the cooling system to explore cooling system problems. Make sure you dispose drained antifreeze properly because the coolant's sweet smell attracts animals and small children. Ingesting the poisonous liquid can be fatal.
• 5Inspect the radiator cap for signs of wear and tear. Erosion can plague a worn out cap. Ask a mechanic to use a pressure tester or an adapter to inspect the cap's pressure rating and operation. Replace a defective cap right away.
• 6Wash and gently scrub the front of your radiator. When you drive, dirt, rocks, leaves and other debris suck into the fins of your radiator causing overheating. Clean it with soapy water, a soft nylon brush, and a garden hose to rinse.
• 7Examine the thermostat for sticking. You can pinpoint a stuck thermostat by constant low temperature readings or peaks between high and normal temperatures. Your thermostat is usually located inside the housing on the engine side of the upper radiator hose.
  
  Read more: How to Troubleshoot the Cooling System in a Chrysler Town & Country | eHow.com http://www.ehow.com/how_4590610_troubleshoot-cooling-system-chrysler-town.html#ixzz1gWR89Vk2

There has been a lot of comments on what could be wrong with your Mini Van Engine. I would not try to trouble shoot this over the internet. Way to much to go wrong with the newer engines. Some of this newer units have a particular way of re-filling water once system is drained. There are issues with the intake manifolds that cause the engine to develop hot spots from too lean mixtures, I could go on and on. I would suggest that you take the vehicle to a good repair shop and have the issue properly diagnosed. Will save you a lot more in time and money to have it properly cared for. Unless you have the tools and money to just change the parts until you find the issue!

Thanks to all who have replied...Matt...and I may have poorly described my problem. I will try to make clear the problem. The engine was overheating...I removed the thermostat to remove that from the possible problem. I started the engine and allowed the engine to run until the temp gauge came to normal operating temp. then the fan came on...No abnormal functions were observed at idle speed and warm up to normal operating temp.

If i drive the engine The temp gauge falls BELOW normal operating temperature and the radiator boils over.... The Question was , What are common failures for Mini vans ,by Chrysler, that have these symptoms.....Thanks Matt

Try some of these:

1. 
   
2. The Chrysler Minivan Fan Clubwww.chryslerminivan.net/
3. 4th. Generation Chrysler Minivans: 2001-2007 - The Chrysler ...forum.chryslerminivan.net/forumdisplay.../38-4th.-Generation-Chrys...
   
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You need the thermostat. Just buy a new one and install it and then retest the vehicle.

The temp falling below as the engine boils over is indicative that the temp sensor is not contacting the water in the jacket, hence the drop in temp, which is probably caused by air voids as a result of the boiling. The fact that your vehicle is overheating to the point of boiling can be a coolant problem. If that is not an issue then check (as stated by a previous post) for collapsing hoses. If the inlet hose is collapsing it may introduce air into the system from the partial vacuum (from the hose collapse) As the coolant loses pressure in the system the water pump will start to cavitate creating air in the system (causing the temp sensor to lose contact with the coolant).

All of this can be caused by improper coolant mixture, weak hoses, a worn pump impeller or a combination of these or even additional items (coolant passages). Some may wish to take it to a "reputable mechanic", but in the dead of winter and a recession I can tell you that a lot of people...well...you get the idea.

The cooling system is the "cheapest" system in a vehicle to troubleshoot and completely overhaul. I would just buy a Prestone reverse flush kit, new hoses, and a couple of jugs of coolant (and some beer to fight off the cold, of course) and overhaul it myself. You may actually discover a real problem along the way, and the light bulb in your head will help keep you warm too!

Finally!! Johnny451, That was my first thought after the T Stat was removed and it still over heated. I did recommend a GA for ya, if the Gods of GA's are in favor. I only know this from past experience with a 351. Same issue. Left side blown.

Yeah, it may be time to have it looked at by a garage and do a leak down or a compression test.

Not a pleasant Christmas gift.

The owner can also check for evidence of coolant and oil mixing.

Sometimes oil will be present in the radiator. Sometimes it only mixes coolant into the oil.

To determine if oil is in the coolant - inspect the radiator fluid by removing the cap and look for oil droplets at the top of the radiator with a flashlight and you can use a swab, too.

To determine if coolant has seeped into the engine oil - Remove the oil filler cap and inspect the inside of the cap for moisture. Sometimes clear water will be present and this is not abnormal. However, if coolant has contaminated the oil the inside of the cap may be covered with a brown foam.

Coolant that contaminates oil can damage the rod bearings, so if found, check with your dealer for recommended course of action. Some cars are more prone to this than others.

Lastly, when an engine truly overheats it will start to run poorly and misfire. This is a critical moment when it needs to be shut down, but an overheated engine will eventually telegraph the situation with a performance drop.

To check for water, even in tiny amounts, in oil, take a small sample in a test tube and heat it. You will hear pops and crackles as the water is drive off as the oil reaches 100°C.

It finds surprisingly small amounts of water......very clearly, or should I say "LOUDLY!"

The test also works for brake fluid and other hydraulic fluids....I am sure that there are oils that it doesn't work for, but I do not know of them - someone else may be able to tell us if any exist......

Normally I'd say to warm it up a bit to open the thermostat but you have removed it.
Are you running the engine without a thermostat? this will surely overheat the engine.The thermostat closes, allowing the coolant inside the radiator to be cooled sufficiently.Then the thermostat opens, allowing the cooled water to enter the cooling jacket of the engine. Without a thermostat, the water enters the radiator, and swiftly exits, re-entering the engine without being sufficiently cooled, this will cause the engine to take a long time to come up to temperature, but nearly impossible to keep cool for long durations.
The thermostat must keep the water inside the radiator long enough to be properly cooled.
As for troubleshooting:

1. Check that ALL cooling fans turn on and off normally.
2. Check that the thermostat opens and COMPLETELY closes properly. a partially opened thermostat is as good as no thermostat at all.
3. Check that the flow through the system is not restricted. (this can be done with an ordinary garden hose)
4. Check for cabin heater output. If the cabin heater output is as warm as suspected, you know fluid is flowing in your system (at least through the heater core), and a blockage is less likely unless it inside the radiator itself. This also will ensure the pump is operating.
5. Check fluid level (this should be #1) in radiator, AND overflow bottle.

With these you should be able to diagnose which part of the system is failing.

• If the heater works, typically the pump is creating flow... Pump's ok.
• If your cooling fans kick on AND off normally, typically your Radiator temp sensor is ok.
• If your fluid level is full, typically you are not loosing coolant, through the head, tailpipe etc.
• If you have verified the function of your pump, fluid level and fans, that leaves the thermostat, radiator blockage, or hose failure.
• Hose failure is easy to test by simply squeezing the hose by hand. If you feel cracking in the hose, replace it, If the hose flattens easily, replace it.

If you have checked all these things and you still have no answers, then check in all the nooks and cranny's in the vehicle for a small gremlin, they are a mischievous species, and experts in the field of hide and seek.

RV,

"Normally I'd say to warm it up a bit to open the thermostat but you have removed it.
Are you running the engine without a thermostat? this will surely overheat the engine.The thermostat closes, allowing the coolant inside the radiator to be cooled sufficiently.Then the thermostat opens, allowing the cooled water to enter the cooling jacket of the engine. Without a thermostat, the water enters the radiator, and swiftly exits, re-entering the engine without being sufficiently cooled, this will cause the engine to take a long time to come up to temperature, but nearly impossible to keep cool for long durations.
The thermostat must keep the water inside the radiator long enough to be properly cooled."

Although l do not know the vehicle, I say the above is all wrong.

The thermostat is located in the coolant outlet from the engine. It knows nothing of the radiator temp & that is of no concern to it. It is only sensitive to the temp of the water in the block. A small hole permits a little circulation when it is closed; when the temp rises to operating temp, the thermostat opens allowing the coolant to circulate. It should open to that setting that maintains the operating temperature, unless engine is putting out too much heat to the coolant, in which case the thermostat will open wide.

Removing the thermostat means maximum cooling all the time so the engine may not achieve designed operating temperature; higher fuel consumption and poor performance will result.

"Don't believe everything you read on the Internet!"

Yer not rong there!

You are completely misunderstanding how a car thermostat works. Removing it usually results in an engine that will never reach working temperature.

This is because there is usually a significant amount of extra/over cooling (in a properly designed vehicle), when running within the climate zones the car was originally designed for!

Its far better that way than running on a "knife-edge" when the cooling can just about cool the engine only on cold days.......

It has happened to me years ago, a Volvo I had bought took ages to get up to working temperature, I opened the thermostat housing and found that there was a little chain, fitted in the small hole in the thermostat valve and the previous owner had mounted it 180° (horizontally) revolved from the correct (it was slanted so that one side was lower than the other) way and this allowed the chain to go between the lips of the valve, preventing it ever closing, it was really bad on cold days......turning it to its correct position fixed the problem instantly!!

To help your understanding I looked around on the web and found this:-

Any liquid-cooled car engine has a small device called the thermostat that sits between the engine and the radiator. The thermostat in most cars is about 2 inches (5 cm) in diameter. Its job is to block the flow of coolant to the radiator until the engine has warmed up. When the engine is cold, no coolant flows through the engine. Once the engine reaches its operating temperature (generally about 200 degrees F, 95 degrees C), the thermostat opens. By letting the engine warm up as quickly as possible, the thermostat reduces engine wear, deposits and emissions.

Here:-

http://auto.howstuffworks.com/question248.htm

I have direct experience with a missing thermostat...

The engine took forever to warm up, but once warm, It never cooled. The water was constantly circulating through the system, and never had a chance to cool. The water has to remain in the radiator at least long enough to bring the temp down, With no thermostat, my experience has been that it will eventually overheat (depending on conditions (driving city/hwy etc). This is only based on experience, and no theoretically based assumptions.

I very well may be wrong based on theory, but my real world experience tells me otherwise.

Don't forget that many car engines run the electric fan for anything up to 30 minutes to cool down the water AFTER the motor is shut off.....

The reason being is that engines actually heat up after shutting off. you do know and understand why I hope? You will only notice it on cars without an electric thermometer, or ones that still work with ignition on, but a stopped engine.....if you need an explanation, just ask, many here can answer....

So its no surprise that an engine takes a long time to cool down, basically they all do!!

I'm not sure where you got the heating up after shutting off tangent, but anyway...

All I know, is that if your thermostat is either stuck open, or missing, your car will eveltually overheat... unless, the weather outside is frightful, and frigidly cold... and even then...

I dare you to remove your thermostat on a hot summer day and go drive around the city for a few hours... try it and tell me how it works out for you.

I know exactly how it works out, been there done that...

Just saying...

And no, I disagree, the engine does not "Heat up" once ignition has stopped, heat transfer does occur long after the last cylinder has finished it's last power stroke, this is absolutely true... The heat will continue to dissipate for a long time, depending on casting material and volume, but no heat is being introduced to the system. You almost make it seam that you are implying that the engine continues to create heat, which is obviously not true.

"So its no surprise that an engine takes a long time to cool down, basically they all do!!"

Agreed, but I fail to see the correlation with an engine cooling down once shut off, and a thermostat operation while running. I'm fully aware of all thermodynamic principles, calculations and theory's, so let's just leave it at that.

Firstly, an engine where you have removed the thermostat will either take a long time to warm up, or it will never reach working temperature, eventually possibly running on a cold start rich mixture which will a) cause emissions to be really bad b) wear the engine as the oil film on the cylinder walls is destroyed.

End result is a lower MPG and early engine demise.

Engines are designed to run correctly at a particular temperature......

How come you did not read that link I posted for you before? That explained it well......anyone here (almost anyway) can explain this for you!!

CAR ENGINES DO NOT OVERHEAT WHEN THE THERMOST IS REMOVED!

They overheat sometimes when the thermostat fails, if it fails closed.......

The reason for the water heating up when the engine is stopped is simply there is a lot of latent heat in the block, cylinder heat, pistons and oil, all of which "migrates" into the water and as the cooling system is stopped (motor not running), it can often cause a 20°C rise in temperature as seen on the gauge.

A car cooling system needs the water to circulate to carry the heat energy released, into the water, to be given up in the radiator.....its that simple......

Can anyone else chime in here that understands car cooling systems and help RVZ717 to understand what he has failed to do up to now?.....stop just lying around and laughing your socks off!!!!

I partially disagree with you Andy. An engine without a thermostat can get hotter than it should.

The thermostat not only regulates the coolant flow into the radiator it acts as an engineered obstruction in the cooling system to ensure that the coolant is pumped completely through all the cooling galleries in the engine.

When the thermostat is removed there is a risk that the coolant will not be forced by pumping through all the galleries which results in stagnant coolant eddies and localised hot spotting.

In order for the heat to be removed from where it is generated in the engine the coolant must be kept moving through all the galleries.

The thermostat allows for cooler coolant from the radiator to be diluted by controlled exchange with the hotter circulating coolant to maintain an acceptable mean operating temperature throughout.

Having said that I would still much rather have no thermostat at all than a thermostat that is stuck shut. Removing the thermostat is a temporary stop gap measure to prevent overheating caused by a stuck shut thermostat only not as a general cure for overheating. One doesn't repair a choked radiator by removing the thermostat.....

If a thermostat has been diagnosed as stuck shut and removed as a limp home measure it should be replaced as soon as it is practical to do so.

Ice storm or heat wave the thermostat has a role to play in uniformly regulating the correct operating temperature.

If your temp gauge goes up in a big way don't panic. You can continue driving until it is safe and convenient to pull over and check the situation. A hot engine will keep going as long as there is enough oil in the sump to burn. Actually they go really good when they are (uniformly) hot, that's one more reason to have a thermostat in place and an oil cooler, dry sump, hi flow oil pump, a big oil reservoir and I'm raving now.

Cheers

The thermostat either stops all the flow (barring the small hole that allows some of the heated water to circulate and activate the wax in the thermostat eventually), part of the flow as the engine starts to warm up, to a free flow......

The only place where water needs to be forced (sometimes even with a thermostat it doesn't get through without help) is the heater core. Some cars need to have the from jacked up to finally get the air out of that!!

That I have seen, your scenario I have not!!

All the engines I have maintained were always fully cooled with simple filling.....thermostat or no thermostat.......I am sure that somewhere there is a shit engine from maybe 50 or more years ago that reacts like that. A modern engine? I think not!!

I have read dozens of Hayes Manuals over the last 45 odd years, but never have I seen your problem mentioned.....perhaps you would be so kind as to direct me to one that does mention this....or a reliable website......thanks in advance. Always ready to learn from a reliable source....

While I cannot cite a Haynes, Chilton, Motors, or Bentley manual specifically mentioning this overheating-without-thermostat issue, I CAN state that I have seen several mentions of it, especially in regard to aircraft conversion engines such as the Geo. One possibly relevant factor is that the installation usually has a quite small radiator, as every ounce of weight that doesn't HAVE to be there is a detriment. Dwell time in that core is critical, and some homebuilt aircraft completions have required adding a thermostat or other restriction to slow the flow (maybe a few impeller vanes should be removed from the pump instead!).

How about some proof please?

Proof that I saw mentions? That would only push the question off another by step, and probably (and justifiably) be even less convincing to you. I am no longer a member of the forum, so not sure whether I can retrieve any archives from a few years back. Gave it a very cursory attempt, but couldn't go back to when I was active there; not sure why. I did attempt re-joining, but will have to wait a day or two even to see whether that is approved. Place was likely either "FlyGeo" or "FlyGeoUncensored", both Yahoo groups centered around use of Geo and Suzuki engines for homebuilt aircraft. [If I had known that this was going to come up, I could have bookmarked the info! Too late now...]

An aside: IMHO, shop manuals are the WRONG place to look, in general, for information regarding results of a missing thermostat. They are written from the premise that the car is factory-stock, not modified. Troubleshooting procedures assume that some part, assembly, sensor, etc., has failed or is defective, rather than being entirely absent due to removal by a previous owner or mechanic. The nearest I have seen was for air-cooled VW's, where the manual might advise that you make sure that the thermostat is hooked up and working the vanes (or the inlet ring on early upright engines). Even then, they would be more likely to cite warmup speed rather than any other possible consequences. A more logical place would be something like the "How to Keep Your Rabbit Alive" (same basis as the John Muir versions for air-cooled series), or the books on hotrodding / increasing performance. Some of these are sufficiently well-regarded as to be trustworthy sources (again, in my opinion).

I am even less convinced than I was before.

Your answer was about what I expected......so no surprises there.

OK, fine: I said that I (had) seen mentions of the overheating-without-thermostat issue (post #70). I did NOT state either that I supported, or refuted them. Here is a fairly typical discussion regarding the topic: http://www.garagejournal.com/forum/showthread.php?p=431867. Like most, it has people coming down on each side of the issue; usually there are posts stating categorically that dwell time in the radiator matters, and others stating categorically that it doesn't, and likely still others stating categorically that faster flow is always better than slower [in effect, calling for even further reducing dwell time]. Most such discussions (Google "overheating without thermostat", and discard the ones starting with "My engine overheated; I removed the t-stat and it still overheats") will eventually have someone chime in with a view that says that an orifice should be placed in the line as a restrictor instead of using a thermostat, and there will soon be categorical statements on that facet as well. Someone will chime in with a claim that says that although the coolant temperature will fall without a t-stat, the oil temperature will increase, showing that the burden has been shifted there. Finally, some will also touch upon an interesting point: with computerized cars, if the engine doesn't warm up within some expected time, relative to ambient air temperature, the control system may put the car into a limp-home or other non-standard operating mode in order to "correct" the problem - granted, I suspect those will normally be designed to PREVENT overheating, rather than encourage it . The point being that the engine, radiator, thermostat, pump, and coolant are NOT the entire system involved: some discussions say that too-cool radiators with embedded transmission coolers may cause shift-point problems because the system managing it stays in warm-up mode. Those Geo engines I mentioned almost always did use the fuel-injection computer and harness, sensors, etc., but I don't think that their systems were sufficiently sophisticated to make this a factor.

No comment on why I think that absence of such mention in a shop manual is irrelevant?

Andy,

I should apologise for the obvious grief that this is causing you. You seem to be coming from a place of hurt...

I'm really sorry that my Jeep Cherokee was a good car.

Hey man, Don't mean to push your buttons...

All I know is it happened to me... many times.

Had a small 4 cyl chevy truck, with a rebuilt engine/trans. It had some electrical problems when I got it, so it only cost me 500 bucks. It would almost always overheat on long trips, or long duration city travel. Water level was always great, coolant looked perfect.

So I decided one day to do the thermostat... lo and behold, there wasn't one in the housing. I bought a new thermostat for the truck, installed it, and it stopped overheating.

I have no explination for you other that that.

Good Day,.

Andy,

Your proof/testimonials, as per your request:

http://www.ehow.com/about_4597044_engine-thermostats-overheating.html
http://forums.evolutionm.net/evo-engine-turbo-drivetrain/481050-can-thermostat-elimination-cause-overheating.html
http://www.garagejournal.com/forum/showthread.php?t=32411
http://www.agcoauto.com/content/plugins/p2_news/printarticle.php?p2_articleid=191
http://www.sr20forum.com/turbo/239606-driving-without-thermostat.html
and countless others...

An excerpt from one of the links:

"Removing the thermostat will NOT increase cooling. An engine without a thermostat will flow too much coolant to the front cylinders and may deprive coolant to the rear cylinders. Operating an engine without a thermostat can cause severe hot spots that may not show up on the temperature gauge. The sensor for the gauge measures temperature only in a small part of the engine. Rear cylinders could be severely overheating and not be revealed on the temperature gauge.Removing the thermostat can also cause erosion damage to the radiator and heater core. The increased velocity of the coolant flow can easily wear through the thin metal tubes. This is far worse in a dirty system, full of abrasives, from lack of care."

Seeing lots of testimonials like this:

"I had a 65 Plymouth that I took out the thermostat and it certainly did overheat. Now maybe in all models it won't, but I do know that it will in some cases. Even a stuck open thermostat will restrict it enough to cool a engine."

In Closing:

I say we end this now, by saying neither answer is correct 100% of the time, and depending on the particular engine in question, it may or may not overheat without a t-stat.
That fair?

It really depends on the environment, the engine, service that the engine is undergoing, and the cooling system itself.

You can't make that broad stroke of a statement because different vehicles behave differently to the absence of a thermostat depending on the factors I listed above.

It may be true in some case and not so much in others, if at all.

I will give it a try, but I do not know anything about engines.

When an engine runs, it produces heat - you can feel it immediately at the exhaust pipe - and also the engine starts to heat up from the inside (combustion chambers- valve openings- exhaust manifold)

In a water cooled engine - without water or (not enough)- these temperatures will be higher than the admissible material limits and will cause the engine to fail.

What is cooling the engine?

Water and oil (and eventually air that is forced along the body) - and the water has the main job to exchange the heat since it has a flow out to the radiator. Some engines however have also an oil cooler that can work next to the radiator or even the AC condenser.

From birth, cars get a specific volume of water, radiator cooling surface - mechanic cooling (fan) and a water pump to make this water circulate to have sufficient (read over dosed) cooling capacity.

The main REGULATOR - is the thermostat. This has been built to open when the engine runs hot and replaces the water IN the engine with the same amount of cooler water to cool it down to the work temperature.

Apart from the fan etc... the thermostat restricts the water from the radiator to run in whole to the engine, because if that happens the engine will run too COLD.

Today it was 20 degrees Celsius here, but sometimes it is 50 degrees and very humid - Removing my thermostat results in a COLDER engine and also makes my car heater come up very slow.

Hope this helps?

"When the engine is cold, no coolant flows through the engine."

Not true, Most engines have a bypass passage where some of the flow does circulate when the T-stat is closed.

FYI

I gotta say coolant mixture or collapsing hoses with the temp drop. But if it was me, I'd be calling some dealers, and talking to the service guys for some common issues.

problem is in temperature switch which control cooling fan which start and stop automatically depand upon temperature.replace it

Radiator condition is ok check for radiator internal choke.

One more possibility I haven't seen mentioned: at least some of the earlier (we had an '89, a '96, and a '98) Chrysler-product minivans used a plastic pulley on the water pump, and the pulley was molded over a metal core. After a few years, the plastic in some of them developed shrinkage cracks, permitting the pulley to wobble, or even to spin on the core. If you can reach the pulley (lower right, close to the right front tire and inboard), try to wiggle it; if there is perceptible play, it can be in the pulley, or the pump itself. If you can actually SEE the shaft of the pump, you may be able to see which is moving relative to the rest. Replacing the pump is a miserable job, in my experience (3.6 liter V-6, automatic trans), unless you get lucky and the five bolts that hold it in place all come out readily. Usually they are corroded in place and will break before turning, even after liberal application of penetrant over several days. The plastic pulley, and the proximity to the lower structure of the body ("frame rail" equivalent) prevents use of a torch. There is no easy way to drill one out, again because of such limited clearance. At three years old, your van may not be such a problem. Putting the van up on ramps helps access, and removing the fender liner will help you reach it.

The power steering pumps on them were MUCH worse, requiring removal of the exhaust system and heat shield in order to wiggle the pump out through the tunnel region; the pulley core was pressed onto the shaft, and it might take several full teardown-and-reassemble procedures to get it positioned properly.

I had a chrysler that was overheating like that and it had air in its line and had to be filled just so with coolant .and their was a hole that could be accessed with a screw driver near the front of the engine for letting the steam out of it and what triggers it is taking the radiator cap off at the wrong time or something like that I wish I could be more specific about it ,but after seeing it happen a few times I started taking the cap off to release the air in the res . myself before driving it.I hope this is clear enough to you its kind of hard to explain it, it was such a mess.

Head gasket dude.

Any water in the oil?

In my experience temperature senders still work even when there is no water in the jackets. The heat still conducts nicely through the sensor body.

I would try to verify that the water pump is moving fluid. Since the thermostat is out this should be simple. Remove radiator cap and let idle. You should be able to feel fluid moving through radiator hoses. With regards to a blown head gasket, your exhaust will show white smoke and smell sweet when first started, if the gasket is blown. Try to let it cool and sit for a few hours, and then carefully study exhaust. Also check motor oil for "milk". Good luck

For the OP: when you say the radiator boils over, is it steam or just hot water? Is it boiling over into the overflow tank or out the cap? Do you see leaks any where else? How many miles are on the van? Not that it couldn't happen, but at being 3 years old I find it hard to believe hoses would be failing already.

In addition to the answers for the above questions, try to get a hold of an IR thermometer and point it at the upper hose once the engine has completely warmed up and find out that temperature (if the thermostat is working correctly this is your temp rating).

If that checks out OK, have a good mechanic check your coolant for traces of exhaust gases and/or oil residue. If residue is found, you found your problem (warped head).

Can I ask, is the rad cap OK? is it turned all the way on (typically you have to push down and then turn some more)? If not it could be causing the very symptoms you describe. The one thing I would recommend against is throwing parts at it, cause it will get very expensive very quick - even if you do it yourself.

I haven't bothered to read most of the posts here because I only would like to pose a question:-

Why does any american ever buy any vehicle from Chrysler Corporation?

Just reading CR4 has given me the insight NEVER to consider such vehicles......not even as a present!!!

Am I alone here with that opinion?

That's an argument one could make on every man made item. I for one only select items that are going to hold up for ever using my Armenian made Crystal ball for a guide to selection.

Maybe I just got lucky. I picked up a Dodge Caravan off the side of the road that was for sale 6 years ago, for $1800. It just passed inspection last week, I haven't done a thing to it but change the oil, and it just turned over 255,000 miles.

Leaky valve cover gaskets are my biggest gripe.

I'd rather have a Chrysler product than a Chevy Cavalier!

Oddly, the 2010 JD Powers ranking puts Ford and GM at the top of the class, with Ford even beating Honda.

Sadly, the problem with quality, like lightning, is that it is not evenly distributed. Chrysler was found to be lagging far behind its domestic counterparts.

The reason Chrysler sells cars is that most consumers really do not look at the data and make an analytical decision when it comes to buying a car. In almost every single case buying a car is based predominantly on an emotional basis.

Simply put, we make a decision based on an emotional response and then cherry pick facts that will back up that decision.

However, I must be off the normal distribution curve because my emotional response when viewing most domestic vehicles parallels that of ingesting spoiled potato salad.

We can't aford a Benz...

Andy,

I take major exception to that comment. Chrysler makes Jeeps... You are not saying anything bad about a Jeep Wrangler are you?? I own one, and it's been the best vehicle I've ever owned. Just sayin... Careful with those blanket statements.

Actually, I was being very unspecific, my apologies.

I would not buy or drive any US made car......a jeep being high on the list due to its extreme cost here with both repair, maintenance and not the least being its extremely high fuel consumption when petrol engines are installed.....diesel being better but not usual.

living in a heavily forested area of Germany, with many hunters, I have lost count of the number of hunters who have bought Jeeps, kept them for a year and sold them at a loss. They usually buy either a Subaru or a Rover if they are not that well off afterwards and are really happy ever after.....

Its cheaper here to run a top Mercedes or even a Rolls than a Jeep.....they also go wrong afar less often.

A friend of mine was the chief mechanic for Chrysler in Bad Nauheim (where Elvis once lived!) for some years, I had to translate the documents for the design fixes from time to time for him as he couln't read English well.....I know Chrysler well.....sadly.

My neighbour had a big Chrysler company car, it spent more time in the shop than on the road.....he was always given a tiny Chrysler to drive while wiating for parts for the other one.......

Many years ago they took over Rootes Cars, UK, after that they only produced really crap cars in the UK from a previously first class designer and builder of cars of the day....Engineered well, but upper management/Financially poor....

If its any consolation, I won't ever buy ANY Italian or French cars either, even today, in spite of some really fantastic Engines/Engineering, the finished quality is simply awful......I would rather have a Tschek (?) car like the Skoda......its got mostly VW technology, desig and finish....

You shouldn't get old without getting a bit clever.......

My Jeep Cherokee experience is different.

Very comfortable, sure footed, went like a cut snake and stopped real quick.

Reliability wasn't a problem for me. My operating environment is far worse than Germany. Maybe I was lucky.

Fuel economy? Pathetic really but I didn't care. When the car was running it was making money.

I sold it as it was surplus to requirement eventually. Yes, at a loss but what do you expect with any car. It made me more than it cost. Cars are consumables.

Andy,

I drive (older) French cars (Peugeot 505s) and find them exceptionally reliable.

On Saturday I was speaking to a fellow who works as a Auto electrician for a VW dealer here in Melbourne Aus - He said that in the workshop he sees lots of VW Touregs on the hoists with lots of problems - he said the the gearbox has 11 microprocessors (if I remember the number correctly) driving it - to me that sounds ridiculous!!!!!

All new cars - irrespective of make- are becoming so complex that they will get written off with minor problems because the faults are becoming so difficult and expensive to diagnose.

The engines and bodies may be good for 20 to 30 years and 1,000,000km but if the ancillaries fail and become unrepairable in 5 years or 20,000km - manufacturing and disposing of them becomes more of an environmental problem than the older cars which may not be quite as efficient in their operation.

What I look for in a car is:

Functionality - will it comfortably and safely carry the people and goods I require where and when I want

Durability - will it do the above consistently for 10 to 20+ without a major failure

Maintainability - will all the required maintenance over the above period be easily done (preferably mostly by myself) and be affordable (parts availability, etc).

Reliability - will it perform without frequent failures or excessive maintenance over the above period.

Safety - good designed in but not intrusive active and passive safety features (handling, roadholding, impact absorbtion, etc) such that excessive numbers of airbags are NOT required to protect the occupants.

Afforability - I must be able to afford to own(buy) and run(registration, insurance, fuel and maintenance) the vehicle on my meagre salary.

Looking around the recent motor shows I cannot find ANY vehicles which tick even most of the above boxes........... The best compromise I have found so far are my 20+ year old Peugeot 505s......

Difficult to diagnose, yes. Impossible, no.

The difficulty comes with the lack of knowledge and experience that these new control systems require.

The expense comes from there being so few technicians/mechanics/engineers who are able or willing to gain the knowledge and experience.

There will need to be some cross discipline skill migrations to occur. eg automation and process engineers would not have any trouble diagnosing automotive systems if they have access to the technical information, proper tools and demand.

Maybe the apparent scarcity of the required skills exists because there is not much call for these skills, due to the improved reliability of the new vehicles there is little or no opportunity to learn or gain experience,

It will work out with time.

These systems are modular and fixable and, if the recreational automotive engineering industry is any indication, totally learnable. There is some amazing new technology and knowledge being applied to the art of going really fast by folk who do it just for fun. Tuning and mods have never been easier....carburettors are on vintage machines these days. It's quicker,cleaner and easier to remap an ECU than to rejet a complex carb...

11 microprocessors in a German gearbox? Sounds like a bit of an exaggeration borne of frustration on the part of the technician. Maybe 11 IOs..... It can be bewildering to the newly immersed.

Steam locomotive mechanics are becoming harder to find and cost a fortune once you find one who is good. Must be difficult too.....

I have two cars, neither of which has any electronic control (apart from the alternators and 1 radio). One is 50 years old and the other is a 15 year old mechanically metered manual diesel. Both 4x4. I can't afford a new car. I'd really like one though

Hi Wal

I agree with you, however the fact remains that the new cars are much more expensive to maintain - simply in manhours involved - most are front wheel drive - changing the timing belt is a case in point!

A friend who owns a workshop had a Renault people mover brought in by a car yard showing a gearbox fault but driving perfectly. Using the factory diagnosis software they finally determined that it was either a faulty sensor, or a broken or disconnected wire, but nothing told them which sensors or wires were related to the reported fault - all they could do was null out that reported fault in the vehicle's processor and and sell it 'as is'.......

I would like to replace my old diesel engine with one of the new ones in a north-south (rear wheel, drive) orientation.......in my 1987 505...

The other issue is parts availability - most manufacturers now only support a model for one or two years after production ceases, and woe betide you if you want anything obscure, not to mention the myriads of sensors and processors scattered all around the new cars!

You are not alone in that at all in my book. Also never ever buy a Chevy Silverado unless you want a great truck with no frame in a cpl years. I will never ever buy another Chevy or GM product. I will by Toyota truck in the spring. Forget FORD, even though they didn't take the bail out money, their bodies rot faster than my Chevy Frame.

How about the Ford Ranger....hang on that's a Mazda.

Sounds like head gasket blown, If it's "boiling over" with the thermostat out then it points to a build-up of pressure hence blown head gasket giving the same symptoms as boiling.

Bazzer.

With regards to the heating problem have the radiator cap tested. If by chance it is only venting out to the catch can it will hold a negative pressure in the cooling system causing early boiling. This may be why the gage is not indicating high heat. I also would consider a leaking head gasket as it will introduce gas into the coolant chambers preventing cooling from taking place and elevate the temp. With the engine up to temp and the rad cap off rev the engine to see if there is circulation in the radiator. It should be obvious if the thermostat is operating. My F150 heated up while under higher than normal load and the problem was the radiator restricted with some sort of build up.. New rad fixed that issue. Do a systematic check as already suggested. Keep cool.

If the thermostat and fan are both working, it may be that your radiator cap will not hold pressure. When the engine heats up at highway speeds, the cooling system pressurizes. This can cause the problem you're seeing if the radiator cap cannot hold the pressure. They're typically pretty cheap. Try a new one and see what happens.

I tested the water pump...Ok...I allowed the engine to warm up and then ran the engine AT 2000 rpm..and what to my wondering eyes should appear ..Steam arising from the engine..No Santa..However the heater hose has a pin hole in it and without the pressure of higher rpm the problem is not seen..the hole is in the metal section of the hose not the rubber portion....Thanks to all who replied...Matt

Way to go!

Matt3477......... 1

Forum.............. 0

Excellent!!!! Nicely spotted.

Thanks for actually bothering to share the conclusion to this quest.

Sadly, many don't bother.....

AHEM, that was #2 on my check list, thank you very much...lol

As it was on mine as well...

I dreamed about it. Does that count?

Depends... was it a nightmare?

Yes, as most of these threads become when we all try to demonstrate our superior knowledge of subjects about which some of us know very little.

Thermostat smermostat. Who cares?

Auto makers don't put thermostats in cars because they're sexy. They're there to do a job. What else do we need to know? Dead‑Horse‑Theory.jpg

Here's what I absolutely, positively know about a thermostat, and I challenge you to refute this. Without knowing the specific capacities, operating conditions and flow characteristics of a given cooling system, in a specific environment, all you can really know about a cooling system's performance is that removing the thermostat from the system WILL INCREASE the amount of flow through the system.

All else is speculation.

GA

" A bad thermostat can lead to issues such as overheating, low heater output, knocking or pinging when accelerating, poor fuel economy, high idle speed, an electric cooling fan that runs continuously, and abnormally low-temperature gauge readings. These problems will not only cause problems for your wallet but could also leave you stranded on the side of the road in the hot sun."

http://www.nascar.com/2008/auto/cct/05/20/car.care.thermostat/index.html

How true...

Unfortunately, in this case, "bad" is a poor choice of words.

The article does not differentiate between a "bad" closed thermostat and a "bad" open thermostat. So, it misleads in that it doesn't identify the cause of each "bad" symptom, but just lumps all symptoms together.

Poor explanation in my book. Too general.

It was a general statement, not a comprehensive evaluation...Simply stated...Stuck either in an open position or a closed position? A closed thermostat valve will cause the engine to overheat, harming the engine and potentially destroying the head gasket, while an open thermostat valve will over cool the engine, causing it to work much harder than necessary.The symptoms for both an open and closed stuck thermostat valve are relatively easy to tell. A closed thermostat valve (overheated engine) will be indicated by your vehicle's temperature gauge plunging into the red. This may happen slowly or quickly, and wintertime driving may make this symptom less severe . An open thermostat valve (underheated engine) is indicated by a car not putting out as much heat through the vents as it should, and by automatic transmission vehicles having difficulty shifting to higher gears. The latter may be more difficult to tell in summertime, when heating vents aren't used...

I know. Just nit picking.

Years ago, they failed in the open position, quite safely.

The wax ones generally fail in the closed position, dangerous.

Some have a sort of safety device whereby if they open (or try to) over the normal working temperature, they lock permanently open to show that they were not the original cause of the overheating.....water loss or whatever....

Wow;

I wanted some simple help to an overheating problem...and this simple and..by the way answered problem has been resolved. The written discourse has deteriorated into a silly pissing match. I would expect much more out of a group of engineers. Most of you have replied to another engineer's statement and not the original question. If you read the original question, much of this BS ,by most all, would be seen as totally unnecessary.

Try and raise the level of discourse..or run for Congress...Matt3477

Yes, you're right.

They're all a bunch-o-jerks. Except for you and me.

Glad you found the leak. Just goes to show, there are more failure modes than "engineers" here.

Be glad you don't own a Chevy Cavalier.

Yeah Matt, I was kinda surprised myself. I did notice sometime back that you found the problem (glad you found it, btw), and here we are days later, pissin' in the wind

Why would you be surprised? I can see how a newcomer might think we get side tracked, but you should know by now...........................this happens more than not. Everybody wants to get in the last word.

Maybe you guys should start your own forum, then you can kick out any answers not to your liking. Just kidding.

Speaking of last words, Bye.