Timing belt skipped on me (1 Viewer)

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4Ruster

2LT Sufferer
SILVER Star
Joined
Dec 14, 2021
Threads
57
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496
Location
Kelowna, BC, Canada
Last night I was driving home from a friends house when all of a sudden the exhaust and intake got really loud. I pushed the clutch in and the engine died on me. Turns out the rubber seal for the timing cover got caught in the belt and must’ve slipped the timing. However I cranked the engine over and it turned fine and kinda ran, but loud exhaust and intake like the valve timing was off so I killed it. Pushed it home as I was only a couple blocks away.

The next day I went to investigate and I found that the cam gear was off 1 tooth backwards, and the injector pump was off like 5 teeth. So I pulled the belt off, and replaced it with a new belt, lined everything up, hand turned it over fine. So I went to fire it up and there was lots of valve clatter and intake noise was a little loud. So I pulled the valve cover off and all of the clearances had like half a cm of clearance.
So I tightened all the valves to 0.25mm intake, 0.43mm exhaust, and it runs fine, but it’s a little slower and the EGTs are a couple hundred degrees hotter accelerating, blows a bit more black free revving so I’m thinking maybe timings off slightly or valve clearance isn’t perfect.
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Any idea why it skipped a few teeth? My main concern would be that it will happen again. Was the tensioner new?
 
Any idea why it skipped a few teeth? My main concern would be that it will happen again. Was the tensioner new?
The timing cover is damaged at the top and as a result the rubber seal is cut up there, it got caught in the belt finally and that’s what skipped it. I pulled the seal out of the cam gear, it was all wrapped up in it. I took the seal off so now nothing should catch. Now there’s a bit of a gap around the whole cover so I’ll have to be careful not to get water in there, will probably have to keep an eye on the belt since it’s open to the elements.
 
Okay, I just did a compression test.
  1. 325
  2. 310
  3. 350
  4. 345
Toyota recommends 455psi+ but the minimum pressure is 284psi. Maximum pressure difference is 71psi. I'd say the valves are sealing fine, I know there's a bit of blowby and I think the headgasket might need changing soon as its leaking oil from between the block and the head.

I think I'm really lucky.
 
The excessive valve lash is a concern. Are the adjusters all similarly extended now? What could have moved?
 
The excessive valve lash is a concern. Are the adjusters all similarly extended now? What could have moved?
Yeah they’re all adjusted roughly the same. I have no idea what could have moved.
 
Although it is possible I’ve always had the timing off a tooth. I remember a few months ago I did the valve lash and they were all way too tight. Maybe now that I aligned the cam properly, now the valves are too loose because they’re sitting on the cam properly for TCD.
 
I did do the compression test when the engine was dead cold from sitting for 2 days, would that make the results lower at all?
 
I did do the compression test when the engine was dead cold from sitting for 2 days, would that make the results lower at all?
cold VS hot will usually be different, but typically lower when hot..
the valve lash being off has me wondering too.. did you do that compression test after re-adjusting the valves? also is it possible you adjusted them on the wrong stroke ?? ( there are 2 TDC's per cam revolution )

lastly, you may want to rig a cylinder pressurization test to force air into the cylinder and test the rings/ valves on each one.

I will be doing my timing belt again on my 2l soon, I can take some compression readings when its apart and share here for comparison
 
cold VS hot will usually be different, but typically lower when hot..
the valve lash being off has me wondering too.. did you do that compression test after re-adjusting the valves? also is it possible you adjusted them on the wrong stroke ?? ( there are 2 TDC's per cam revolution )

lastly, you may want to rig a cylinder pressurization test to force air into the cylinder and test the rings/ valves on each one.

I will be doing my timing belt again on my 2l soon, I can take some compression readings when its apart and share here for comparison
Yes I did the compression test after adjusting the valve lash to spec. If I were try and adjust the valve when I was 180 off don’t you think it would be tight because the cam is pushing on the rocker?
 
Some compression testers can read lower on a diesel if there is significant volume before the check valve.
 
I had that issue with my CX500 motorcycle engine and everybody I tried to reason with told me I was wrong.. but when I shortened the hose it read better !!

It makes sense, as it's esentially increasng cylinder volume. On a 22:1 compression diesel, even a tiny bit makes a difference.

With diesels, compression is easy to tell by how they start. So if this situation were mine, I'd be looking for even compression numbers between cylinders, cold starting and blowby to tell condition of the motor.
 
Here’s a cold start video then. A little shaking at first. The rattling is just the exhaust.
 
That seems like a pretty decent start to me. Was not smoking at all out the exhaust? The little missfire on first start could be some air still getting into the lines.

I have had low compression in a diesel before, and it took a lot longer than that for the bad cylinder to start firing.

Did you check your engine oil for sparkles after the timing belt incident?

Pull the engine oil cap off while its running and just set it in the hole. If it blows completely off, and you see big puffs then you have problems. If it just rattles in the hole, then things are probably fine in terms of blow by.
 
That seems like a pretty decent start to me. Was not smoking at all out the exhaust? The little missfire on first start could be some air still getting into the lines.

I have had low compression in a diesel before, and it took a lot longer than that for the bad cylinder to start firing.

Did you check your engine oil for sparkles after the timing belt incident?

Pull the engine oil cap off while its running and just set it in the hole. If it blows completely off, and you see big puffs then you have problems. If it just rattles in the hole, then things are probably fine in terms of blow by.
Thats a relief. I did check and there doesn't seem to be any metal bits or anything. I've noticed its always had a slight misfire on cold starts. For all I know one of the glow plugs cold not be heating up the same as the rest. There's a little puff of white/blue smoke during a misfire but thats it.

How's this for blow by?
 
Not familiar with the 2L. Are they a non-interference engine?
If belt skipped on an interference engine, I'd be worried about bent valves
Interference yes. Although I know it can run with the timing off a tooth as I had it like that in the winter when I did the belt, turned it by hand and noticed it was off. There's no noticeable loss in power, cold starts the same, rattles the same.
 
This makes me wonder if maybe the cam gear moved more than you think?
I’m hoping not. It is possible it skipped more but then the piston pushed the valves, and in turn, the cam gear back. But like I said I’d probably notice a difference in the engine by now, and it feels fine. If I wasn’t driving the truck when it slipped, and someone fixed it without telling me, I’d never even know it slipped.
 

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