2001 Dodge Intrepid Overheating

Could be plugged radiator tubes after all those years. Bottom tubes will be full of crud first.

Power flushing may help, but the tubes may need to be "rodded out".

Or just replace the radiator. I've been suspecting that the system could be partially clogged - perhaps in the radiator as you have suggested or in the heater core.

I'm also thinking now that, the heat I felt on the lower radiator hose could have been from radiative and convective engine heat, so I'm going to definitively check the thermostat tomorrow.

Thanks for your input, Lyn!

Hi, also when you shut it off make sure the radiator is hot all over. Run your hand all over it looking for cool spots. A hand held laser thermometer is great for this. Taste a drop of exhaust water that comes out when you first start. Make sure it doesn't taste sweet!!!! Make sure there are no coolant bleed plugs in the cooling system to let trapped air out. Good luck.

"Since there was coolant flow, I'm assuming the thermostat was indeed open."

There is always some flow through the thermostat, it's not a safety shutoff after all. I'd bet that the thermostat has a stiction problem. That would explain the sudden rise in temperature during the 15-18 minute period. If it won't open slowly/properly, then it will build up heat and pressure until it moves suddenly.

Since you are planning on checking it tomorrow, why not just replace it. The cost of a thermostat is pretty cheap in the scheme of things.

My 2 cents

Check the fins on the radiator for obstructions to air flow.....make sure you have 50/50 mixture coolant and water.....If the maintenance has been performed and the radiator has been flushed....check heater core for heating to verify the water pump is working....change thermostat.....change water pump....

http://www.youtube.com/watch?v=t3HFV5MosPA

Replacing the thermostat and flushing has worked for me every time.

You can use the commercial flushing stuff from the parts store, or as a cheap, "green" alternative, drain most of the coolant and top it off with regular white vinegar. Run the engine until warm, shut it off and let it sit for a couple of hours.

When flushing, make sure to pull the hoses and flush the heater core separately, in both directions. You'll be amazed at how much crap builds up in there. The pistol grip water nozzles work best.

Because there is fluid flow does not mean the thermostat is functional.

When was the last time the system was drained and flushed? I will guess - never. This should be done every two or so years along with the brake fluid.

When was the last time the thermostat was replaced? I will guess - probably dinosaurs were not yet extinct.

Those two items are almost the very first thing to do, but you should also be thinking...

Sometimes a bad head gasket will cause overheating, so I would inspect the oil in the engine for coolant. It usually settles on the oil fill cap as a brown or greenish watery scum. If there is clear water it is not from the radiator.

Look for oil in the radiator fluid. It will form droplets at the top of the radiator after the cap is pulled.

When you first start the car, with the windows down, and back up into the exhaust, do you smell a sweet syrup odor? If so, that could be antifreeze seeping into the engine's cylinders when the car is shut down. Perform a leak down test of the cylinders to find the bad cylinder.

If a head gasket is bad it can push exhaust gasses into the coolant system, causing excessive pressure and boiling.

Next, check for collapsed radiator hoses. If any are soft to the touch when squeezing they need to be replaced.

If those three tests pass, then go back and do the flush (actually, have a shop do it so you don't have to mess with disposal of antifreeze), replace the thermostat as a matter of default, and see if the problem clears up.

If not, you may need a new water pump.

My last thought is a bad radiator.

I'm with you on that leaking head gasket. Every time my vehicles have had these specific problems and fixing all those other things didn't work, it was the head gasket...or a cracked head. Probably not the latter in this case, but possible. What indicates a leaking head gasket is the boiling in the tank and that it happens so quickly after cold startup. Nothing was said about how the engine acts when the vehicle is driven. My guess is that things get MAJOR hot. Have a pressure test done on the system to eliminate guess work.

It's not that the antifreeze boils, but exhaust gasses are getting into the coolant system.

When the vehicle is shut down, the cooling cylinders draw coolant back into the cylinder and when restarted you get a hint of maple syrup smell from the exhaust, which is the smell of antifreeze.

Check the airflow through the radiator. I had a pickup that would overheat. I found that crud had built up in the fins reducing the airflow. I found it only after replacing the radiator. It was hard to see with the shroud in place.

"The bottom radiator hose got hot, so I think there was flow (from the water pump)."

To make sure re-do the above test. This time leave the radiator cap off. Best if you drop the fluid level down out of the neck of the radiator where the cap goes on. Should be able to see pretty good flow as the radiator gets hot and thermostat opens.

First to check is the belt tension on the water pump pulley. Also if the pump spin free with no belt on it.

Then if low to no flow I would check the thermostat before looking for a blockage.

if the system is under proper pressure it wont boil....that's the whole idea of being preassurized

A vehicle cooling system under pressure can still boil.

It just will not boil at 212deg F (or 100deg C).

The whole reason of pressurising the system is to raise the boiling point so that the engine can run at a temp that is most efficient for the engine. This setting is close to boiling point of water. So by using a pressirised system, you have more "head room". ie more tolerance of mild overheating situations without boiling & subsequent coolant loss.

Ive had an impella drop off a water pump once that caused overheating.

There are a lot of good answers here, but what to do first.

1. Pull the thermostat, put it in a pan of water, and heat the water. Using a thermometer watch for when the thermostat opens. Replace if higher than specified. Usually 180 F on stock thermostats. It should be fully open by the rated number.

2. If the thermostat opens fully then that is not a problem but flush the system with any good radiator flush while the thermostat is out.

3. Try the engine again after flushing, with plain water, but without the thermostat and see if the problems repeat. Yes, it will fail quicker with just water if the problem is there, but it is better to know the problem exists without subjecting the engine to the higher heat the antifreeze show. If the problem does not show up, drain the water and install antifreeze and thermostat.

4. After this it is a crap shoot. I can go on from here easily. Many more possibilities but most were already discussed. Give us more data.

Yes, an old trick.

However, if you go through the trouble of pulling the thermostat, just replace it with a new one. They are so cheap that it doesn't make sense to mess around.

If you replace it with a new one, you must test the thermostat before installing. I have come across an incredible number of bad thermostats within the last 15 years. Before that, they hardly ever went bad and the new ones were good. At first I thought this was just the thermostats from the discount autoparts but it appears that all the brands are having trouble. The "Wax Motors" inside the thermostat are the problem and do not extend fully to open the thermostats. They operate part way and quit. This is contrast to a thermostat that goes bad after years of use. If the wax containment leaks they will go suddenly from working fine to not working at all. Basically, the was expands pushing the thermostat open.

As Anonymous Hero and Justajo stated it could be a head gasket or cracked head. There is a simple test for a bad exhaust gas leak and this sounds bad based on the time to overheat. Remove the radiator cap and thermostat, ensure the system is full of water and start the car. If you have a bad exhaust leak the fluid will shoot out of the radiator like old faithful.

Good analysis and advice. My mechanic told me about another way to test this (he told me this about a year or so ago).

There is also a dye to check for exhaust gasses that is added to the coolant. It's blue when there is no leak, but turns yellow when there is one.

This would've been a quick and easy test and it doesn't require getting to the thermostat housing.

Could be, but if the leakage is relatively small, you will only see bubbles, grey bubbles, full of exhaust gas....

The speed of the bubbling is dependent on the size of the leak.....for old faithful, you will need a bigger leak!!

I worked on these cars and they are famous for engine issues. Go to an Intrepid forum and check out the comments. 2001 Intrepid with its reputation on engines may not be worth investing much money in. Of course check out as best you can many of the qualified comments on this forum..

Also check your oil to see that there isn't any water in your oil. A leaking head gasket can cause over heating.

Thermostat stuck open is the most common cause and if it needs replacing get one from the dealership, don't go for the after market thermostat, they don't last at all.

A thermostat stuck open "OVERCOOLS" the engine, the opposite of the problems here.....

Yes you're right.

Thanks, everyone for your answers. Sorry I haven't gotten back here until now.

I was going to replace the thermostat per Killowatt, and started in, only to find out that to do that, the alternator must be removed first. The thermostat housing is not on top of the engine block. I didn't have the right place or time to do all that, so she took the car in to an auto shop.

The problem: Blown head gasket.

When she told me that, she then proceeded to tell me that how earlier this summer, her car overheated (gauge was redlining) when she was coming back here from Seattle. She said that, since she didn't have any water she couldn't stop right away and it was hot like that for some time.

Anyways, thanks everyone for replying.

Mike

That's a case where turning up the radio or applying black electrical tape to the warning light won't help.

Your reply AND signature line work really well together

Thank you for reporting back. It is always nice to have all the facts before beginning isn't it. I don't know how many times as a field engineer, someone came up with a symptom they noticed but didn't mention because they didn't think it mattered, after I finally found the problem.

Thanks for letting us know.

Don't you wish she had let you know about the overheat episode first!?

Lots of good information was provided with some good advice.

Some things to consider:

1. Here's the giveaway that it wasn't a thermostat. The car was run for 18 minutes before the temp gauge went up. If it was a thermostat, the temp would've gone up sooner.

2. Very unlikely to have been a bad radiator, but an '01 should have an aluminum core with plastic tanks. They typically start to leak, but usually don't clog up like the older ones.

3. Water pump was an unlikely possibility since in 18 minutes time, it would've overheated.

4. Head gasket/warped head would've been the most obvious, but it typically occurs with overheating. Since the original post didn't mention this, it made it difficult to come up with this conclusion. When the information was later provided, it all makes sense.

Note that there are times when an aluminum head/iron block design will have a head gasket problem without overheating. This occurs due to the expansion/contraction of dissimilar metals and the stress to the gasket (which is between the two metals). If you research this, you'll see many engines that have suffered from this problem.

Great that the problem has been identified and fixed, but not all possible reasons were covered!

Incorrect ignition timing and/or fuel with too low an octane level will cause overheating and can even cause cooling water to be expelled. (Old Faithful effect!)

Typically incorrect timing will cause overheating pretty quickly, but it could cause an overheating problem 18 minutes later. Too low octane would be the same as above. Running lean due to a weak fuel pump or partially clogged fuel filter is possible. Ditto for an air obstruction in the intake system - too rich condition. If driving and overheats, could be dragging brakes, low tire pressure or bad wheel bearings (brakes dragging). Clogged cat, baffle in muffler broken or cracked exhaust manifold. The last one can cause cold air to hit the exhaust valve, which will allow it to leak, which then causes a low compression problem. Which brings us to a cracked compression ring too.

Though these are possible, the highest probability was the head/head gasket damage from overheating. I have a client with a Land Rover Discovery with this problem.