Recommended Automotive Hard Parts Service Intervals-Reality In All Cases?

I bought a new timing belt for my old Hyundai and fitted it in the boot (trunk) .

It's been handed down to my Daughter now and the timing belt is probably still rattling around next to the spare wheel.

I'd have fitted it but the engine mount is bolted onto that end of the engine and it wasn't going to be a quick 'pop off the timing cover' job .

Del

Attempting to extend the mileage on an interference engine past the recommended timing belt change is asking for trouble. One of my son's friends did just that in his Nissan truck, and it stopped running suddenly one day, while cruising down the highway. Son tried several things to get it going again, then checked compression on the cylinders and found several bad ones. Pulled heads and found bent valve stems, and slight gouges in the top of some pistons where the valve heads interfered with piston travel. Friend gave truck to son. Son had a valve job done (9 valves were bent)($475 U.S.), and was planning to put the heads back on over the weekend.

Better to change the belt than to be compressionless.

I replaced the (toothed rubber) timing belt on a Ford Escort I once owned when I got 'cold feet' after about 2¹/₂ x the recommended interval (in miles). The old belt looked brand new - absolutely no sign of wear.

The timing chain should be replaced at service intervals when the possibility exists in an overhead cam engine that the valve stems could be bent by hitting the pistons when the belt breaks. Overheating or wear can cause this.

The belt is more likely to break than the chain, but a chain can stretch. This will cause the valve timing to go out of specification.

Look at the cylinder head (when removed from the block) to see if the valves extend below the plane of the head surface. Rotate the camshaft and see if the valves enter the combustion chamber.

If the cylinder head is aluminum and the block is cast iron, the head will expand when overheating occurs. The chain can break or jump the cogs on the cam sprocket and the engine will be ruined.

don't know if tey make a direct or after market set of head gaskets for this machine but after you pull the heads and check the valve stem conditions lok at the seats and check the angles on them and the heads. when you have done that if you can get two gaskests one a full thickness the other 2.5mm thick put the head on and torque it down. before firing the engine up invest in some coolant leak detector material and the blue light for finding it. don't go any farther with putting the unit bak on the track until you find the leak, the head could go anytime and you will be out in outer slobovia trying to find a tow. or if it dies on a free way you and the rig might not make off the pavement.

'da bear

Once took a trip from Edmonton, Alberta, Canada, through Salt Lake city, over to Albuquerque , New Mexico, Up to Denver, Over Sheridan , Wyoming, thence to Great Falls Montana, and North home to Edmonton. The next morning my wife was driving kids to school and the timing belt broke. I was so glad that it happened in Canada because I never saw a single Nissan Micra in the US so parts might have been a challenge. The garage had another case of a broken timing chain/belt in the shop at the time. In that case the valves interfered in such a manner that the force twisted the camshaft and broke it in half.

Needless to say I will be very diligent in changing timing belts/chains in the future.

When I was working as an auto mechanic, I had a work order that said replace timing chain on a Datsun 2000 roadster. When I opened the engine, I found the chain to be in perfect condition, but the guide rails were worn, one rail broken, and the sprockets badly worn. So I just replaced the bad parts.

The timing chain on these engines slapped on the timing rails until the tensioner got oil pressure. Neither the customer or the incompetent service manager knew that this rattle was a characteristic of this engine. The later L16 and L20 engines which were in the new cars being sold did not have the timing chain rattle.

So the customer was unhappy and the service manager had me install a new chain. Of course it still rattled even though it was running good as new.

When performing an overhaul, I would replace all belts, hoses, and thermostat. Normally, those were the only parts that I would routinely replace even if they were still serviceable.

Snave, that is similar to what I discovered. The stationary rail was broken in two (2) pieces, but of course it was held in place by the taut chain. In the end, the only real difference I could notice that when all was pressed tight, the chain was not nearly rubbing itself as it did before I replaced the timing set. Again, I attribute that to the grooves worn in both rails.

The rubber gearbelts always concerned me, as it seemed that every vehicle we owned where the engine was equipped with these things was of the "interference" type that can incur a lot of valve train and piston dome damage if the belt breaks or jumps phase by a tooth or two. For these few automobiles I did have the belt replaced or tensioned at the recommended intervals as it was not worth the risk.

A Porsche I once owned had a small air duct from the belt cover on each camshaft bank so the negative pressure of the intake would pull a bit of cooling air past the belt. I never saw another design that used this idea. This engine also used a hydraulic tensioner that was filled with opposing Belleville washers that provided the first level of compression, and these were adjustable via a jackscrew. Very elaborate design when I have seen units that are much more simple.

I agree with you about the replacement of rubber parts such as hoses, as they are easily damaged by ozone and motor oil and this damage is not always apparent. They are relatively cheap parts, as well. That was my logic for replacing an otherwise good water pump, but I did see the telltale sign of a very slight seep after I removed it. That would be a pisser to act as a cheapskate and have to replace it in a month or two.

So, I drove the truck to work today, and it ran well. I'll change the oil in a couple of days as it no doubt has tiny pieces of gasket rubber and a bit of antifreeze solution still floating in unless it has all been trapped by the filtre.

Best Regards,

Ing. Robert Forbus

What about the coolant loss? I didn't see that you had stopped that. You also didn't say if the pickup has a coolant temp gauge on the dashboard...and, if so, whether the gauge tends to run on the hot side on average. Of course, since you have not owned the truck since new, you might no know any "standard" temp reading by which to compare. In that case, and assuming its an analog gauge, and assuming midrange temp reading would find the needle levelled at horizontal...then after engine warm-up, does the needle tend to hover above (hotter than midrange), or below horizontal on the temp gauge? The answer to this (whether the engine tends to run hot, or "normal" or below) could give a clue to improving or eliminating the coolant loss problem.

Guest, and the coolant loss. The main leaker was the radiator. In the absence of a true pressure test, I determined that the core was probably okay, as was the upper plastic end and the lower plastic end. The leak was in the area where a channel of sheet metal is hem-folded to pinch each cap to the core and seal the assembly. From the appearance of the unit, this was the main leak. Quite slow, but nonending.

When I closely examined the water pump, I noticed the telltale coolant stain in the area of the weep hole. It was not dripping, but the evidence proved that the bearing's seal was compromised. How long would it have gone; that's anyone's guess.

I did not do a hot water test with the thermostat, as the units tend to be inexpensive-sometimes. In my case, the thermostat was quite expensive, and I will explain. I of course remove the water neck (inlet), removed the original thermostat and cleaned the area of the RTV sealant. The new (not OEM) thermostat seemed to fit just fine into the recess, so I applied a coat of RTV sealant to both mating surfaces and installed the three (3) cap screws. I gradually tightened the screws, being mindful of even torque. As I made the last tightening sequence, an ear snapped from the zinc metal water neck.

Drat. So, after the holiday, I order a new water neck and OEM thermostat from the Nissan dealer. I carefully clean and double-check the mating before I apply the RTV sealant. It was perfect. I was able to install this thermostat as it should be installed. No leaks. But, the non-OEM thermostat (about $8.00) cost me $21.00 (OEM replacement for it) and about $42.00 (OEM new water neck). I examined it carefully, and it was a few 1,000th's too thick at the flange. This placed a lot of stress on the ears of the water neck. Lesson learned-don't buy a non-OEM thermostat for this truck. The parts manager at the Nissan dealership said he was with the business for nearly twenty (20) years and had seen this happen at least twice before.

So in the end, I have driven the truck for about 120 (one-hundred twenty) miles on two warm days, without a visible or measureable coolant loss. The truck is equipped with a temperature gauge, and it is in its normal position-slightly below mid-point. Interesting to note: after I test ran the engine at my home, I sprayed the area of the front differential and sway arms with "Gunk", an emulsifying agent and drove the truck to the car wash. I left the splash pan off, as I had washed it previously. The temperature gauge indicated between mid-range and "hot" until the truck was up to 50 (fifty) miles/hour or so, then dropped to normal. I had a bit of stop-and-go until I got to the car wash, and it would run from warm to normal, depending on my speed.

For this vehicle, the spash pan makes a big difference regarding proper air flow through the radiator at slow speeds. Of course when I arrived home I returned this unit to the truck, and the engine temperature stabilized and has remained stable.

So, I purchased a new battery two (2) months ago to replace my old unit that was just past eight (8) years old. I have practically a new cooling system, and a new timing chain drive. The compression is obviously decent, as the truck does run okay and seems normal. New hoses and belts (about four months ago). Will this truck be like my old Toyota that went over 440,000 miles and required me to replace four (4) batteries, one (1) alternator, one (1) starter, make two (2) carburetor overhauls, and replace the clutch one (1) time? Nope. It's not that reliable. But, I feel that driving it up to two-hundred fifty (250) miles/week it should last me for at least five (5) more years. It would have to go a total of nineteen and one-half (19 1/2) years to break even with that Toyota-a darned good little pickup.

Best Regards,

Ing. Robert Forbus

Drat.

My words, but far less euphemistically and far more verbose when I sheared off the head of one T'stat retaining bolt while properly torquing it...to the wrong spec as given in a certain aftermarket service manual, the publisher of which whose dba which starts with H shall remain un-named.

The renewal work you have done is certainly impressive and, focusing on where my original question was leading, your description of temperature readings is much as I suspected...as in, tending to hot, and seemingly inconsistent with engine use vis-a-vis ambient conditions. Likewise, the radiator failure you encountered is precisely the same failure which necessitated my own recent radiator replacement for my '87 Ranger--that and fan and fan clutch. The leakage, like with yours, had been issuing undetected from the seam on the side, near the return radiator hose. It was high enough so that there usually remained sufficient coolant (below) to prevent extreme overheating; because the rate of leakage was most pronounced after, both, topping off and after engine warm up, escaping fluid (after warm up and start of circulation) would evaporate almost quickly as it seeped out and flowed downward and, thus, remained undetectable in spite of frequent close inspections to discover where fluid was slowly being lost. My temperature gauge reading experience was not unlike yours...something which puzzled me since, having owned the truck since new, I recalled its early history of tending to run cool--below mid range on the temp gauge. I tended to dismiss the change as "normal" wear and tear. Replacement of the radiator turned out to be a fortuitous necessity, in that removal of the old radiator facilitated close inspection of its cooling passages/fins, particularly on the engine side that is not readily visible when installed with cowling. What I saw within the cooling passages was years of gathered accumulation of...stuff, to the point of virtually full blockage—and this in spite of periodic hosing and blowing out on the front side fins over the years; what I learned, and what the majority of folks probably never give much thought to, was the need for periodic clearing of cooling fins, front and back, in order to maintain both engine cooling and radiator longevity. In other words, I believe that the radiator's decreasing ability to transfer heat and pass cooling air is what overstressed and finally led to seam failure...the radiator had finally been a little too hot way too many times. I also believe it (the air blockage) played a part in prematurely damaging the (quite expensive) five blade plastic fan (hairline cracking around the mounts) as it labored to draw cooling air, only to move hot air behind the radiator...and seldom if ever idled because the viscous clutch never received the benefit of cooling air. I discussed this with the Ford dealer who agreed and advised (from time to time) unbolting at the top mounts and leaning the radiator towards engine in order to purge (blow or wash) unseen dirt from the cooling fins. So this will be a new scheduled maintenance item (maybe every few years) for me from now on. The test, the proof, came when, after installing the new radiator with pristine cooling passages, the temperature gauge has not yet reached even the halfway point on the gauge...at any speed or driving condition; I expect that it will not do so even as temperatures here reach and exceed 100F. It's as if the truck is new once again! Funny thing...I'd never before seen any published recommendation for such thorough cleaning (and straightening) of radiator air flow passages. I guess it's normally assumed the car will be replaced long before the radiator finally succumbs; probably also assumed that gradual degradation of cooling will be seen as a sign the vehicle needs replacing with a new one.

Oh yes! I fully intend that the manual publisher will pay in full measure for the tear down and extraction or repair of the t'stat hosing retainer bolt and/or threads. And I will be obtaining the name of that publisher's agent for process service just in case the invoice I send is not promptly paid. I'm hoping they'll realize that a invoice in the $hundreds is preferable to damages, direct and consequential, in the 10's of $hundreds.

FYI most Honda 4-cylinder engines are of the interference type. Most Toyota 4-cylinder engines that use a belt are of the non-interference type. This was true for all Toyota MK1 and MK2 MR2s and other cars up to about 2000. I am not sure about later models.

Dear Robert Forbus: re: your question about changing parts for new, when the old ones measured so Good. My answer is : Since You have the New Parts @ a reasonable price, Change them & keep the Old Parts well cleaned & covered totally with light coating of grease, only as a back up spare package. The reason I'd do this is the Steel, Aluminium, or Cast of any metal has had its Strength Changed by Years of Much Temperature Change. As said above this would be done "Just Because You Were Able To Get the Replacements Now, But what if you Can't Get Them @ A Later Date." 70 yr old Retired Diesel Mechanic, still Occassionally Get My Hands Dirty, Helping A Brother In Need. Carl

I will update my post with another repair I made today. When I reassembled the front engine cover, I of course replaced all rubber sealing units such as the small "pucker" seals and the crankshaft sheave seal.

Recently, the truck began to leak a lot of oil and there was no apparent leak source I could easily find. It puzzled me how it could leak so much oil, as my first suspect was the crankshaft sheave seal (carefully replaced and it fit properly on both journal and bore) and secondly the oil pressure sending unit as I have seen them spring a leak.

My investigation began like this: I removed the engine splash guard and the belts, and placed a sheet of waste cardboard underneath the engine bay. I started the truck and carefully crawled underneath it. I spotted a steady stream of fresh oil creeping from behind the crankshaft sheave. I wiped the area clean and it reappeared.

I stopped the engine, and removed the crankshaft sheave. I removed the seal, which still had an excellent grip with the bore. I slipped it over the journal of the crankshaft sheave, and it felt fine. I had a new seal and I installed it. I washed the messy underneath of the truck, and the leak is now gone. For how long-I cannot say.

But I will say this; if it reappears I will replace the crankshaft sheave as well because it has a normal groove worn into it from the sealing lip. This time I installed the seal about 1,0mm from its perfect position in order to avoid the groove. I know there are "Speedy Sleeves" available to repair the worn area, but if I can purchase a new sheave it may be about the same price. It will be about the same amount of work, as the sheave must be removed for either option.

That's how I spent a good part of my Thanksgiving day, so I'm off to take a motorbike ride before it becomes too cool.

Best Regards,

Ing. Robert Forbus