Cracked Head caused by over tightened Valve Cover?


#1

I’ve got a '95 Toyota Camry, 2.2 L4 [5SFE] engine with 115,000 miles. I had been going back and forth to my mechanic over the last few years trying to stop oil leaks. About 2 years ago, one of these leaks was from under the valve cover. They replaced the gasket, but still leaked. Took it back and they tightened down on the valve cover bolts. I drove it this way for a few weeks and there was still an oil leak. They resurfaced the valve cover and reinstalled, and at least stopped the leak at that point. [More leaks were further down the engine, but that’s another story.] Anyway, 2 years later and I’ve developed a crack in the cylinder head, down in the #2 spark plug tube. Coolant was leaking in causing misfiring, of course. Last resort was adding stop-leak into the radiator, which worked for a while, but the stop-leak sediment is still coming into the tube and now some coolant too, and engine has started to run poorly again, so now it’s trash. The main question is if the mechaninc caused the head crack by over tightening the valve cover? His remark was that the valve cover would have cracked before the head if it was too tight. From doing further reading I couldn’t find information to confirm my suspicion. I seems the main concern from over-tightening the valve cover bolts is with stripping the threads, or squeezing the gasket abnormally, but no mention to cracking the head. Plus, being 2 years before the crack occurred I would think not, however, the crack is in the spark plug tube, which is what the valve cover bolts on top of. Is it possible that the over-tighten lead to a small fissure which developed over the 2 years to a larger crack? I don’t feel that at 115,000 miles this should have happened yet. The car never overheated, and work was never done on the head. These Camrys, I’ve heard can last over 200,000 miles. The owner remarked that sometimes there can be an imperfection from the factory that eventually comes out, “like measles”. I wanted to laugh in his face, but of course I didn’t feel like laughing. So, do I say Adios to this place or are they right? [Whew, sorry, I didn’t mean to take that long]


#2

I really doubt it. He’d snap off the valve cover bolt before cracking the head, I’d think.


#3

I would never say it cannot happen but it’s in the realm of being so remote as to be ridiculous. Your search for the guilty will be fruitless. Stuff happens. Mileage based claims are also without any merit. Any car can last 200k miles or 20 miles. Mileage is virtually irrelevant because it is dependent on a whole host of conditions. Just envision two different areas; NYC versus Iowa farmland. Is 200k miles the same for both vehicles? It’s a good thing you didn’t laugh in his face…


#4

I think the head crack started first, interfered with the head flatness which made the valve cover mismatch and leak oil.

Blown head gasket could be on the horizon.

I would get a head from a salvage yard and take it to a good machine shop for an overhaul.
At 115k miles the block should be in good shape if you’ve done the oil changes.


#5

These Camrys, I’ve heard can last over 200,000 miles

Yes. They can. Yours didn’t. Any time you see a “can last x miles” statement remember that some vehicles last longer, and some don’t last as long. You’re one of the unlucky ones.

I’ll also point out that you said it’s been two years since the valve cover work. You don’t believe the mechanic when he tells you that an imperfection can come out over time, but you do believe that an imperfection in the mechanic’s work can hide for 2 years before presenting itself? That’s logically inconsistent.


#6

Well, thanks for the opinions. I didn’t mean to sound so firmly agianst my mechanic, since I didn’t want to believe it to be his fault. We’ve been going there a long time, but new mechanics have come into that place recently, so it’s not quite the same place anymore. I did say that I didn’t think something done 2 years ago would have taken this long to surface. Anyway, I’m not going to spend the money to rebuild, since there are other problems to take care of and the car is only worth a little over $2K.


#7

circuitsmith’s theory sounds very compelling.


#8

115,000 miles in 16 years suggests an engine that’s spent its life doing a whole lot of short trips. These are the absolute worst conditions for an engine except for neglect. This is severe use. In your case, the mileage is not an accurate indicator of how worn out the engine is.

Trying to stop oil leaks in an engine this old can be analogous to trying to stop leaks in an old dam where the concrete is beginning to crack away. It’s a losing battle.

Old engines have a lot of opportunities for leakage and for structral failures. Parts wear out and open up spaces where there should not be any, like between the rings and the cylinder walls. Pressure builds behind tired, long-compressed gaskets. Metals become fatigued from billions of poundings from hot explosions. At 3000 rpm your engine parts are subjected to 1500 explsions per minute. That’s 90,000 per hour. two hours a day average would be 180,000 explosions per day, or 65.7 million per year. over 16 years that’s 1.051 billion explosions. Metal can fatigue and begin to fail after that many poundings.

And gaskets work via pressure against the surfaces their sandwiched between. But over the years they become compressed and the pressure disappears.

Yes, there can be a defect in a part that eventually comes out. These are known as “premature failures” and in some cases “infant mortalities”. But any part that has lasted as long as your have has not failed prematurely. It’s lasted its intended lifespan.

Face the facts. You have an old worn out car. It isn;t the shops fault. At some point, the dam can no longer be effectively patched and needs to be replaced.


#9

e got a '95 Toyota Camry, 2.2 L4 [5SFE] engine with 115,000 miles. I had been going back and forth to my mechanic over the last few years trying to stop oil leaks.

Any particular reason you tried so hard to stop oil seepage on a car almost 2 decades’ old?

2 years later and I’ve developed a crack in the cylinder head, down in the #2 spark plug tube.

The spark plug hole is a long way away from the valve cover…it’s a lot closer to the cylinder head bolts. They’re way bigger and are subject to FAR more torque than the valve cover bolts could withstand before shearing off.

His remark was that the valve cover would have cracked before the head if it was too tight.

Yeah, the valve cover is much weaker than the head…much lighter too.

The owner remarked that sometimes there can be an imperfection from the factory that eventually comes out, “like measles”. I wanted to laugh in his face

UAL flight 232 experienced a failure of all three hydraulic systems when a compressor vane failed in flight. “The cause of the engine failure was traced back to a manufacturing defect in the fan disk, which had microscopic cracks due to impurities. (Wikipedia)” These cracks propogated, over several years in use, until absolute failure. So, yes, metallurgical imperfctions CAN and DO take time to exhibit–your mechanic was right. Good thing you didn’t laugh in his face!


#10

Thanks mountainbike, that makes the most sense of all.


#11

Thanks everyone!