Experts needed: Timing belt running toward engine

[whitemike]

Hey all,
Well, pretty deep into my build now, new engine is refreshed and everything is just about to go back together. Only problem I'm still facing is with this damn timing belt.

The timing belt (even after moving it back to normal) will tend to work its way back toward the engine. The farthest it sits is right at the edge (flush) of the cam gears.

What I've checked:
1) Previous owner told me it was the bracket on the oil pump shaft, but that checked out fine. It's nice and tight and compared to my other 7M (that doesn't have this problem) It's exactly the same.

2) Next, I was told to check the crank timing pulley, the rear lip on it sometimes can snap off causing the timing belt to lose its guide. This wasn't the case.

3) Checked the cams and the crankshaft for any in/out play. Everything checked out.

4) I was told it could possibly be the timing tensioner, I don't see how, but It's going to be replaced anyways on re-assembly.


Guys, I'm stumped. Please tell me someone has had this issue and has an available solution for me. I'm ready to assemble the engine TOMORROW and I don't want to put it back together to find that the problem still exists.

Thanks in advance for any help,
-Mike

 

[gofastgeorge]

It does that on my currant engine.
I don't see any problems with it unless it would want to run off the pulley.

 

[whitemike]

It does that on my currant engine.
I don't see any problems with it unless it would want to run off the pulley.

Maybe not immediate problem but the fact is that something is out of spec and it needs to be fixed.

 

[hvyman]

t belts usually go to there own spot not to where you set it. if its not rubbing or falling off its fine.

 

[whitemike]

t belts usually go to there own spot not to where you set it. if its not rubbing or falling off its fine.

It was rubbing the rear timing cover, and getting progressively worse.

 

[IJ.]

Take some pics of the belt and pullies.

 

[whitemike]

Take some pics of the belt and pullies.

Alright, gonna have to do it in the morning. Thanks.

 

[MK-beast]

I would like to know the answer to this as well as I have the same issue with mine except that my timing belt tends to pull away from the engine (Toward radiator).

 

[suprahooked]

If the belt is running back theres a good change the the washer that is on the back of the crankshaft gear has broken free.
I had the same problem and change the gear to fix the problem.

 

[whitemike]

If the belt is running back theres a good change the the washer that is on the back of the crankshaft gear has broken free.
I had the same problem and change the gear to fix the problem.

..
What I've checked:
..
2) Next, I was told to check the crank timing pulley, the rear lip on it sometimes can snap off causing the timing belt to lose its guide. This wasn't the case.
..

 

[giterboosted]

I have the going forward problem and yes mine is rubbing, or at least it was but it's not actually rubbing anymore, but regardless no matter how many times I fix it back to where it goes it INSTANTLY goes back when it is cranked, sorry to thread Jack a little but I'd like answers too.....

 

[whitemike]

I have the going forward problem and yes mine is rubbing, or at least it was but it's not actually rubbing anymore, but regardless no matter how many times I fix it back to where it goes it INSTANTLY goes back when it is cranked, sorry to thread Jack a little but I'd like answers too.....

I had it moving forward on my previous 7m. It turned out to be the front guide snapped off the crank timing gear. Check it out, and get a new one.

-Mike

 

[whitemike]

IJ: I've taken pictures of everything the timing belt comes in contact with, as well as the oil pump driveshaft, let me know if you spot anything. You can see where the belt sat on the cam sprockets.

 

[IJ.]

How tight was the tensioner done up Mike? (tq spec)

Did you lever it against the belt before tightening?

Where's the Oil pump pully?

 

[whitemike]

Not sure, Ian.

Something I seem to have neglected to mention, I don't know how, is that I've never ran this motor.

I picked up this motor a little while ago, It's strong with quality parts inside, but needed some maintenance. Replaced all bearings, main seals, oil pump shaft seal, all related gaskets, cam seals, valve cover gaskets, water pump, timing belt tensioner, thermostat, etc.

I've never ran this motor, but the previous owner is a friend, and I trust what he told me. All I know is what was stated.

You're confident it could have been the tensioner? The new tensioner will be installed tomorrow, and everything is being torqued to spec so far.

Thanks,
-Mike

 

[IJ.]

If it's be over tensioned on the belt that will pull the belt off centre but more inportantly if the bolt has been over tightened it can damage the wall of #1 cylinder

Even at the Toyota spec of 36 ft/lbs I've measured half a thou deflection on a new thickwall casting.

 

[whitemike]

If it's be over tensioned on the belt that will pull the belt off centre but more inportantly if the bolt has been over tightened it can damage the wall of #1 cylinder

Even at the Toyota spec of 36 ft/lbs I've measured half a thou deflection on a new thickwall casting.

Holy shit.

I really hope this isn't the case. Taking the tensioner off, it actually kind of felt loose from what i remember. Either way, what's my options at this point.

I guess I'll just put it all back together and hope for the best. This motor was running (strong) before it was pulled and sold to me.

Thanks for the insight,
-Mike

 

[IJ.]

To paraphrase The Oracle from The Matrix I hate to bring good people bad news Mike, I learnt by accident after trashing my original mint GE block by over torquing the bolt

(could never understand why it had horrible blow by on the dyno at even low boost)

Also for the belt tension just buy a fresh spring from Toyota (they're cheap) and let it set the tension per the TRSM then pull the bolt down to 36 ft/lbs and you're good to go.

 

[whitemike]

Also for the belt tension just buy a fresh spring from Toyota (they're cheap) and let it set the tension per the TRSM then pull the bolt down to 36 ft/lbs and you're good to go.

Sounds good, Ian. I already have the new tensioner and spring coming to the shop tomorrow. Let's hope this solves the problem, and I don't have the blow-by problem of cyl. 1 that you had.

Thanks a lot, look out for my build thread, I have tons of pics. It should be up any day now (once the motor is done)

Time to head off to bed, It's 3:37AM and I have to be back at the shop at 8AM :aigo:

-Mike

 

[CyFi6]

Was the block ever machined without the timing cover being machined? Theres a little spot on the pass side of the bock where the head meets the block, you can actually feel if there is a ridge where the timing cover meets the bock. If its higher than the deck surface it could cause your head to be leaning back in a sense and making the belt ride back.