New Timing Belt Is "Walking"

[venerated]

I just replaced the timing belt on my E30, along with a new belt tensioner. I am in the process of putting the car back together and after turning the engine a few times (to make sure TDC lines match up on the crank shaft and intermediate shaft) I notice the belt is walking on the pulleys.



Belt is flush with rear side of crankshaft pulley.


Belt is walking off this pulley toward front of car.



Anyone know why this could be happening or what I can do to remedy it? Does it have something to do with how the belt tensioner is positioned/tightened? Thanks in advance.

[kronus]

Interesting. There was another thread with a failed m20 due to a belt that tried to walk off the front and shredded itself. Folks in the thread suspected a bad batch of Conti tensioners.

What brand tensioner?

[venerated]

Interesting. There was another thread with a failed m20 due to a belt that tried to walk off the front and shredded itself. Folks in the thread suspected a bad batch of Conti tensioners.

What brand tensioner?

Looks like INA. It's this one: https://www.fcpeuro.com/products/bmw...em-11311468743

[shoshottz]

sub’d... timing job coming soon and need to be prepared for anything like this.


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[digger]

properly seated in the crank gear?
check run out on the cam gear, intermediate gear and idler. something is wonky

[zaq123]

does it go back and forth on those mentioned gears or just walks to where it is now and stays there?

[dnguyen1963]

My suspect is the belt. If the grooves are not perfectly parallel, the belt will walk. I would get another belt to see how that behaves.

[e30austin]

I'm guessing you're using a Conti belt (which I have for many years, without issue), but you might give a Gates belt a try and see what happens.

[venerated]

After more investigation, I think the crankshaft is not reseated all of the way and that is what is causing this. I replaced the seal in there and thought I had it back on, but I released tension on the tensioner and tried to look at the belt parallel. I found that the crankshaft was what was guiding the position of the belt.

Through all of this, I also realized that the pin from the oil pump pulley (? I think that's what it is, middle pulley) was missing a pin that actually made it move the pump, so I found a lot of metal shavings because the pulley was just moving around the shaft instead of moving with it.

Whoever worked on this car previously unfortunately put it back together missing many parts (the timing belt tensioner spring and pin, this other pin, I'm sure I'll find more) so I am trying my best to make sure I have all the pieces by using diagrams from realoem.com.

Once I get everything back together (Have to put another part order in) I will update if that was the issue or if it's something else. I also experimented with the position of the tensioner and found that influenced how the belt was moving, so if someone else has this issue that hasn't replaced the crankshaft seal or knows that it is reseated correctly, try to tighten and un-tighten the two bolts that hold the pulley on til the belt is moving in a straight line.

[digger]

The crank gear should bear against the shoulder of the crank. The large m20 bolt pushes it against the crankshaft

[e30davie]

I don't understand all the comments on different brand making a difference. If we cant trust that the teeth on the belts are made straight then we might as well give up on cars.

Sounds like you have are onto something. In instances like this I personally would take it all apart and start again.

[digger]

Yeah pull it apart start again. No need to buy new parts unless youve found something that is faulty.

[zaq123]

New Timing Belt Is "Walking"

You didn’t answer my previous question. In any event, I don’t think one could set crank gear off, cam gear possibly but no easy way to do it with crank. If the belt goes back and forth - cam gear or inter.shaft gear. If just stays to one side, most likely the tensioner. If the tensioner checks out, gears check out, one of main reasons for the belt walking is an excessive tension (it makes the tensioner deflect on the bearing).


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[shoshottz]

fixed?


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[venerated]

fixed?


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Have been really busy and haven't had time to do anymore work to it. Will update when I figure it out.