96 6.5 belt walking off the tensioner

[tylerandrews]

hi guys just bought my first 6.5l its a 96 k2500 gmc sierra just put new head gaskets in new heads and what not finally got it running but now the belt is walking off the tensioner I've ordered a new tensioner and tried it but the same thing happened it walked off again.. is there suppose to be a bracket there or something I'm missing? i will post pics tomorrow. someone please help!!!!!! thanks guys

[Dvldog8793]

Howdy and welcome.
Most likely your pulleys are out of alignment. Take a long straight edge and line up all your pulleys and make sure that none of them are out true with the others.
I had the same issue and it was a PS pump pulley that was only out by about 1/8 inch.
When you replaced the tensioner, was it the whole assembly or just the pulley?

[tylerandrews]

Howdy and welcome.
Most likely your pulleys are out of alignment. Take a long straight edge and line up all your pulleys and make sure that none of them are out true with the others.
I had the same issue and it was a PS pump pulley that was only out by about 1/8 inch.
When you replaced the tensioner, was it the whole assembly or just the pulley?

i bought the whole assembly and it still seemed like it was out of line.. what would cause the pulleys to be out of line?? and thank you i will get that checked out today and post some pictures!

[Dvldog8793]

Howdy
Any one of the accessories could be out of alignment and cause this.
I would expect it was one of them that was removed and reinstalled when the heads were taken off/installed.
Could be caused by not putting a washer or spacer back in the right spot or something not tightened up properly.
Are these NEW heads or rebuilt originals? Possible that a mounting surface is not the same as the old heads
Put the straight edge on the crank pulley and check the accessories. It could be possible that the crank pulley is moving but unlikely if you did not experience this problem before.
First thing to suspect would be whatever was removed when the heads were done. If I remember right the accessories closest to the tensioner are the alternator and the AC? I would check those and the tensioner first.

[tylerandrews]

Howdy
Any one of the accessories could be out of alignment and cause this. I would expect it was one of them that was removed and reinstalled recently. Could be caused by not putting a washer or spacer back in the right spot or something not tightened up properly.
Put the straight edge on the crank pulley and check the accessories. It could be possible that the crank pulley is moving but unlikely.

the only pulleys i took off were the a/c compressor, belt rensioner, and the altenator. i have the altenator bracket on and the a/c compressor is in place but like i said its just the belt tensioner that looks out of line. i dont no if there is a spacer for the tensioner or another bracket?

[N9Phil]

I would check and make sure that your belt is on all of the pulleys and in the right groves. It seems to me that I had that problem once and I found that I had the belt off by one notch and it would cause this problem.

Phil

[rustyk]

Also while you're at it, check/replace the crankshaft pulley - it's damped, and on mine, the rubber was completely gone. The hammering damaged the tensioner shaft, tilting the pulley, allowing the belt to slip off when the belt got wet.

[tylerandrews]

Thanks everyone for the advice! i checked all the pulleys and everything was fine.. i was just missing the bracket that goes behind where the tensioner actually mounts.. so no more belt walking off truck is running and driving!!! Also could anyone tell me hot the truck is suppose to run at? its currently running at 220-230. Thanks again guys i really appreciate it!!

[Dvldog8793]

Howdy
You are running too hot. In normal driving you should be at 190-195.
If you do a search on this sight there is ALLOT of info on what to check and clean up to fix your problem.
I would not drive it much at those temps.