Did my timing belt jump teeth

JETMAN79

MEMBER
1995 TOYOTA 4RUNNER
3.0L
6 CYL
2WD
AUTOMATIC
250,000 MILES

Vehicle engine shut off while accelerating on road. I couldn’t figure out what was going on until I noticed my two camshaft timing marks were not both at the 12:00 positions, one at 12:00 and the other at about 10:00 and crank at 0’ TDC. Timing belt seems tight but it seems like the belt must have jumped about 8 notches. Is this really possible?

5 Replies

KASEKENNY

MECHANIC
18,907 POSTS

Hi Jetman79

That is unlikely. Did you try to turn the crankshaft one full revolution and see if the marks line back up? There is a chance you were not at TDC on the compression stroke. If you were on the exhaust stroke then one of the valves (exhaust) would be open and that would be about the position.

Just make sure you use the crank pulley to turn the engine over. If you turn the engine over a couple times and when on 0 degrees the cams just don't line up then you will need to correct it because if it truly is that far off I would think you would have some starting issues. Looks like this engine is a non interference engine which is good if this is the issue. That means the piston and valve will not contact if out of time. However, they will have performance issues as I said.

Let me know what you find and we can go from there. Thanks

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Monday, June 3rd, 2019 AT 7:50 PM

JETMAN79

MEMBER
3 POSTS

Thanks for the response Kenny1. Yes, I did turn the engine over by hand several times and the cams would not line up. I should of added that the truck is dead and will not start. Also, coolant was leaking threw a bad water pump gasket all over the belt and I’m thinking that could of helped it slip, it’s just hard to understand how it happened. Could the tensioner be bad or the coolant cause the belt to degrade? The belt just seemed to be nice and tight. Maybe some loosening is not noticeable by touch.

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Tuesday, June 4th, 2019 AT 2:47 AM

KASEKENNY

MECHANIC
18,907 POSTS

Yes to both. The tensioner could be the issue but you will see that the tensioner is all the way out which would indicate a stretched belt. If it is not all the way out and the belt has tension on it then it is probably okay.

The coolant leak can cause a belt to slip. I would repair the leak and then replace the belt, resetting the timing and then turn it over again. I am sure you will be all set at that point.

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Tuesday, June 4th, 2019 AT 6:55 PM

JETMAN79

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3 POSTS

That’s what I’ll do. Thanks for your insight and response. I’m going to replace the water pump gasket, tensioner, and belt, clean everything up real well and see what happens.

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Wednesday, June 5th, 2019 AT 4:36 AM

KASEKENNY