ProudDad

Hello everybody,
I have been working on a friends 91 4Runner 3vze. It had 283k when he bought it. So far we have done full tune up, valve cover gaskets, plenum gasket, camshaft and crankshaft seals, all new timing components, water pump, rear main seal, clutch, starter, alternator, battery and new oil and filter of course. He has been driving it and put about 5000 more miles on it with an oil change at about 4000. Just resently it wouldn't start. Sounded like it had no compression. Checked the timing belt and it appeared to have skipped a bunch but no signs of teeth missing. Bought another belt and got it running again. It drove great that night with no issues. The next morning again it wouldn't start. This time the timing was still good but motor seemed seized. Very hard to turn over by hand. Eventually got it started and did a motor flush. Oil was extremely dirty. He again drove it away and 4 days later same issue again. No start and sounds like timing is off again. Any ideas?

MudHippy

If it keeps happening then someone is doing something wrong. The belt should never skip teeth. Ever. If it does, then it wasn't installed correctly. And/or nobody's figured out why it did it the first time. Hence it keeps happening. Something critical is being missed.

That's pretty much all I can say with any certainty, based on what you're giving me. This is not a common problem. So there is no common answer.

ProudDad

Well I did not mention that my father helped and is a 40 plus year mechanic specializing in foreign auto and has also had and worked on his own Toyota 3vze. I am 100% possistive it was done correctly both times. Hand turned the motor several times to verify timing was correct. Like I said before the first time it drove about 5000 miles. If it wasn't done properly we wouldn't have gotten that far. We checked the pins on all the gears and none are sheared. It felt as if the were a bent valve because it was so hard to turn over by hand but there was no noise once it started. I have heard the sound of a bent valve before. Once the motor was started and flushed out it ran perfect. It even turned over easy by hand. Checked and set timing. Then 3 days of driving a couple hundred miles, runs good all day, go to start in the morning and no compression. Even my father is stumped.

chuckross1957

Since you flushed the engine oil and it came out very dirty, try flushing it again and see how it looks. I'm wondering if a previous owner went a very long time with out changing the oil.

MudHippy

Look...what I'm getting at is this. Without properly diagnosing why the belt skipped the first time, you can't expect it to not happen again. And again. That's what I mean by installed correctly. A critically important part of fixing something is knowing how/why it broke. Until you've got that figured out you're pretty much wasting your time.

It's happening for a reason. Trust me. There's no magic involved.

ProudDad

That's why I am asking. What other possibilities could cause it. Belt is on correct, no pins sheared on crank or camshaft gears. When warm motor turns over by hand and runs good. When it's cold it doesn't turn causing the belt to skip. Could it be the motor is so gummed up?
This is why I am asking for any ideas of what it could possibly be. I felt like you're still trying to say it's installed incorrectly. It is on correct or it wouldn't run fine for a few days then stop. This is the reason I am here. Any other person want to help me out cause this guy hasn't.

GorgeRunner

Is there a belt tensioner? If so, is it working?

ProudDad

Yes everything was brand new installed when we did it the first time 5000 miles ago. Checked it the second and third time. It's the spring and bearing tensioner not the hydrolic one. It's still putting good tension and bearing is still spinning freely.

pcmentor

Was a brand new belt put on after the other new one slipped? The may be damage to the belt that was missed or unseen.

ProudDad

Yes. I thought that maybe the first belt may have over stretched somehow. Bought a new one when we did it the second time.

MudHippy

Did someone forget to tighten the spring tensioner? Because that's THE ONLY way the belt could ever skip teeth.

I can hear the reply now. "What do you mean tighten the spring tensioner?"

The bolt that keeps the spring tensioner from moving. You haven't mentioned that it's been tightened and couldn't be causing the problem. I was going to ask about it. But I'm trying to give your "foreign auto expert" 40+ year mechanic father the benefit of the doubt.

But like I've said already. Somebody did something wrong. We're just trying to figure out what.

Why do I keep saying that? BECAUSE IF YOU DO THE JOB 100% CORRECTLY THIS DOES NOT HAPPEN!!!

ProudDad

Yes the bolt was tightened.

RJR

If I read you right, when (or just before) this problem recurs, the motor is very hard to turn over. Seems like that's a clue. Next time it seems stiff, I would suggest immediately tearing it down, removing the timing belt, and finding out which of the three rotating shafts (crank, or one of the two cam shafts) is resisting turning. That should give you more insight than you have now.