2jzgte timing belt walks off cam gear

[RZTT]

Hi Guys, I have a problem with my car as the timing belt keeps walking off the cam gears at high rpm and rubs against the front timing belt cover. The car is 1995 model JDM spec Twin turbo Toyota supra (2jzgte).

Took the car down to drag strip one night and on the first launch I heard a snap noise coming from the engine bay. Then couple of second after heard this really loud grinding noise when accelerating. Was running 18psi at that time. Shortly after that pulled my cam cover off and saw the belt moved few millimeter off the cam gears and causing it to rub against the cover.

Took the car home then the next day, we put new tensioner, new timing belt, and new crankshaft. And took it for a drive. At about 4500rpm-5500rmp it happend agian. I have no clue what else I could look at?? Is it possible my that the crankshaft mite be moving and cause the belt to walk off the cam gears? OR there could be something bent? Please help guys need the car back on the road asap.

Your advice and help would be appreciated.

Thank You
Manesh

["Z" UTE]

Misalignment of the various wheels and idlers will do this. Is the crankshaft gear as fas back as it should go?, is there a chunk of crud preventing the crankshaft gear going all the way back? Put a dial test indicator on the cam wheel, and check for end float, and front bearing play.


cheers Chuck.

[Mr_Flawless]

End float would be a big thing to check, even a idler support pin bent slightly or cross threaded will sit askew. Other things like a slightly warped cam gear can cause a problem such as this. Dirty or oily cam and crank gears can also cause a belt to walk. I agree with Z ute, best bet would be to run a dail gauge on all the pullys and check.

[RZTT]

Misalignment of the various wheels and idlers will do this. Is the crankshaft gear as fas back as it should go?, is there a chunk of crud preventing the crankshaft gear going all the way back? Put a dial test indicator on the cam wheel, and check for end float, and front bearing play.

cheers Chuck.

HI Chuck, Thanks for taking your time to help. The Idler wheel has been realigned twice to make sure its sitting correctly. As far as I know the crankshaft gear is sitting all the way back. The dail test indicator is a good idea. Never thought of that. Thanks heaps.

End float would be a big thing to check, even a idler support pin bent slightly or cross threaded will sit askew. Other things like a slightly warped cam gear can cause a problem such as this. Dirty or oily cam and crank gears can also cause a belt to walk. I agree with Z ute, best bet would be to run a dail gauge on all the pullys and check.

Hi Mr_Flawless, Yeh i thought i should check the idler support pin, you could be right it may be slightly bent. I had Oem cam gears when it happen and now I'm running aftermarket gears. Thanks heaps Mr_Flawless for you advice much appreciated.

[oldcorollas]

did it only start after changing to the aftermarket gears?
could they flex just enough to cause walk?

[RZTT]

did it only start after changing to the aftermarket gears?
could they flex just enough to cause walk?

no it happend after I put in 264 bc camshafts. Had no issue for a month and as soon as i took the car to the drag strip thats when the belt started to walk. I was still using oem cam gears. Only upgraged to aftermarket gears after the belt issue

[2jzhilux]

Have you measured the thrust clearance on the cams?
Also check there is a washer behind your timing belt tensioner bolt

[CELICASUPRA7M]

my 7m did this once, it was the cam gears had come loose and were leaning back towards the head which encouraged the belt to wander off, def gotta be to do with the cam sprockets,
Obviously yours arent loose but yeah, dial indicators dont lie!
cant see how the crank sprocket would have an effect being so small compared to the huge cam gears tho.

GL with it

[petergoudie]

Is the tensioner spring stretched and therefore not tensioning the idler fully?

[RZTT]

Got the problem fixed guys. Thanks heaps for everyones help. It was actually my ebay cank pulley. Replaced it with Ross damper and now the running sweet.

I got another problem. Boost not holding

here is the link to the thread http://www.toymods.net/forums/showthread.php?t=57086

Hope you guys can help me out agian

[PlacentaJuan]

can you give us some more info on your solution please;

why was the ebay pulley causing problems etc?

wrong part, wrong size etc...

[RZTT]

can you give us some more info on your solution please;

why was the ebay pulley causing problems etc?

wrong part, wrong size etc...

The ebay Crank pulley wasn't Dampened, and it was causing alot of vibration to the crank gear. From all the vibration at high rpm the belt walks off cam gears and snaps the tensioner.

[PlacentaJuan]

sounds pretty serious;

i have been running that undampened (and undersized) ebay pulley for a few years with no problems yet.

however i am very aware of not having a dampener (or harmonic balancer) and will be one of the first things i replace when the engine comes out again.

[RZTT]

sounds pretty serious;

i have been running that undampened (and undersized) ebay pulley for a few years with no problems yet.

however i am very aware of not having a dampener (or harmonic balancer) and will be one of the first things i replace when the engine comes out again.

Yeh i had for a year and didn't have any issue with it till i upgraded my flywheel to fidanza light weight flywheel.

[Mr_Flawless]

just be careful that your not masking a unbalanced flywheel, if it was fine before u replaced the flywheel, i would be taking that flywheel to get its balance checked. the new balancer could just be masking the real problem