Metal Fatigue in Engines of Old Cars?

Could someone tell me how metal fatigue might manifest itself in an older car, say a 1987 or so? Could the overhead camshaft caps break off due to metal fatigue alone, at 176,311 miles, rather than to improper maintenance of the car? Thanks for your help.

Camshaft caps breaking is usually the result of failing to line bore the cam journal when a head is milled flat. I wouldn’t consider that metal fatigue would be an issue on a cast aluminum cylinder head. A heater core would be a better example of fatigue.

Given the number of well maintained antique cars driving around, the type of failure you describe is much more likely due to poor maintenance than age or metal fatigue.

I think the best way to explain metal fatigue is like erosion. You can’t see it day-to-day, but if you really know what to look for, you can find it. For example, in Shop Class as Soulcraft: An Inquiry into the Value of Work, Matthew Crawford describes how an experienced mechanic can point out subtle signs of metal fatigue that would normally escape the untrained eye. If memory serves, Crawford cites an example of valve stems that have been “mushroomed.”

One place where I’ve noticed metal fatigue is on my “the Club” steering wheel lock. When I remove it, I tend to push the sliding part all the way in before I store it and drive. Where the sliding piece comes into contact with the other part of the unit, the metal has slowly bent back in a way that makes it look slightly deformed.

Most mass produced cars built in the late 1990s and early 2000s were built to such high quality that most of them made it to 200,000 miles without any major issues, but yours was built in 1987, during an era when 100,000 miles were still considered a lot, and most people traded-in their cars with fewer than 100,000 miles. After 176,000 miles, finding metal fatigue on a 26-year-old car doesn’t seem unreasonable to me.

As far as how metal fatigue could manifest itself, like in the example I mentioned, your valve stems (the parts that come into contact with the cam shaft) might be mushroomed (compressed at the end and bulging out to the side), your engine mounts might be cracked or weakened, your frame members might be rusty and weak, or the bolts that hold your brake calipers in place might be a little stretched and weakened by being removed and reinstalled. Even your lug bolts could show signs of stretching from repeated removal and installation of the wheels. Don’t forget, everything is at least a tiny bit elastic, and that includes metal. Heck, the cable on my parking brake has probably stretched a bit since I bought my car in 1999.

Thanks, Rod Knox. If the original 1987 Dodge cam caps broke during freeway driving, would it be most likely caused by low oil? With most bearings gone, too? Or could it be something odd that caused it?

I could kiss you, Whitey. You’ve made me feel much, much better. :>) How long do you think a 1993 Buick could last, with good maintenance, mileage-wise? Was 100,000 miles still considered a lot in that year?

Over the years I’ve seen all kinds of engine parts fail. I’ve seen crankshafts/camshafts break, connecting rods break, head/crankshaft bolts break, etc… And this occured on well maintained average mile engines in some cases.

So yeah. Stuff breaks.


On OHC engines the cam journals are usually the first place to starve when oil pressure decreases and a seizing camshaft could break a journal cap. But I believe the term “metal fatigue” refers to the weakening of metal from repeated flexing. My earliest understanding of the term was from a documentary on this plane

That is very good news, Tester. Have you ever seen an engine overhead camshaft cap fall off the end of the engine? The mechanic claimed the timing belt shifted and knocked into the engine, causing the cap to pop off and spew oil. Sounds very weird to me, especially since the timing belt seems to have good tension, still? A 1987 Dodge IS very old, after all; correct? Anything is possible? 176,311 miles was a pretty good life for it?

Rod Knox, could anything cause oil pressure to decrease other than the car being low in oil in the first place? I don’t know what an OHC engine is. Mine is a non-interference engine.

Metal fatigue was an issue in the thirties. Today car component failure is usually due to lack of proper maintenance. In rare instances it is a defective part that was not machined or cast properly.

The most infamous fatigue failures were the wings on the British de Havilland Comet jets, and the Aloha Airlines B-737’s front roof coming off in mid flight, due to an excessive number of landings-takeoffs and insuffucient inspection.

I wonder how many miles is the record for a 1987 Dodge 600 SE? Anyone have statistics? Theoretically, how long could mine have lasted, mileage-wise? If only I had checked the oil before I set out that fateful day. A neighbor had checked it for me not long before and said it was fine, and I had trusted him. Maybe it had sprung a leak.

I have an uncle who is still driving his early 1990s Buick, but how long one should last is beyond me. My uncle is the kind of guy who can rebuild an engine without any help, and his son owns a repair shop. It all depends on a lot of different things, like tolerance for the cost of repairs. If you’re willing to spend enough to keep things working, in spite of how little a car is worth, you can keep it running indefinitely.

I can’t say how long your 1993 Buick should last. There are too many variables. I don’t even know if you live in the snow (rust) belt or in the sunny south. All I can say is that if you keep up with the manufacturer’s maintenance schedule, you’ll spend less to maintain your car than if you wait for things to break.

Thanks, Whitey. I’m in sunny Utah. You are right.

“The most infamous fatigue failures were the wings on the British de Havilland Comet jets, and the Aloha Airlines B-737’s front roof coming off in mid flight”

Let’s not forget the Lockheed Electras of the late '50s-early '60s, whose wings also had an unfortunate tendency to come off during flight. There were two of those incidents.

Whitey, do you know or could you find out what kind of Buick your uncle drives? I found out this one is a Cutlass Sierra.

Odds are that any camshaft issue is related to lack of lubrication for whatever reason.

I just wonder whether all the oil leaked out of that popped cap, and if I hadn’t driven it a bit afterwards, slowly along the right side of the freeway, thinking it was bad gas, whether it would have been repairable easily?

In your post two weeks ago your cam seal or cam plug came out, the engine ran out of oil and the engine seized. The damage was done before you called the tow truck. You wouldn’t have called for a tow if the vehicle in good working order would you?

That engine is obsolete, used from 1986-1995. If your really in love with the car I bet you could find a used engine for $250.

So you think the damage was already definitely done in? That’s good. I have worried that maybe had I not tried to inch it forward it still would have been repairable. But maybe not. However, if it was still driving, even after it had set alongside the road for over an hour, it’s a sign it wasn’t a bad oil pump, or so someone said. They said had the oil pump broken, I could not have gotten it to start. I have thought that maybe had I not driven it that little bit it would have been easily fixable, as a non-interference engine. But after it set for an hour no doubt all the oil had leaked out, and maybe I burnt it up at that point. I need to hook up the battery and see if the pins jump up and down? I don’t recall what they are called but a nice friend took everything out and put them on a piece of wood in order, so if I want to replace it I can. He says the bottom of the engine might be okay. But if the bottom engine is fine and I put on a new top engine, there could be a problem with the old and new engine parts being mixed together; right? The new might put too much stress on the old part? That is what my friend said, although he did this once and had to pay only $300.00 for a new rebuilt engine, or that is what I think he said.