1996 Pontiac Grand Prix Noise After Timing Belt Replacement

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1996 Pontiac Grand Prix GTP 3.4 overhead cam. Had a purge valve issue, but was replaced, resealed a oil leak at the oil pump drive shaft plug, but didn't remove head or cam housing, just the intake. This was a year ago, not related to this problem.

The engine ate the timing belt for the 4 overhead cams. The belt was replaced, engine started, but very noisy and stalled, not to restart. Next the cylinder heads were removed. One replaced because of cracks, and both completely rebuilt. At this time the o2 sensor was replaced, a complete tune up, starter, just a basic really going over on wear items.

Now with all the repairs made regarding the timing belt failure. The engine now starts and runs with power. But has a very loud buzz saw or chain saw noise coming from the front of the engine. I removed the serpentine belt eliminating all the accessories. Removed timing belt covers to verify timing belt is not rubbing. I'm a professional mechanic by trade. I've work on Toyota industrial equipment for last 22 years. Not familiar with this 3.4, but with info can repair as to factory procedures.

Looking at a picture breakdown of engine, there's also a timing chain and tensioner driven by crank to balancer shaft, which drives timing belt. My gut response is this may be it. Could the destruction of the timing belt damaged this chains tensioner, and now it's slapping the cover? Or maybe you know this is something else. Due to the fact these are difficult cars to work on, I don't want to repair something that isn't broke.

ANSWER:

If you have verified and are completely sure that nothing was rubbing on the timing covers, I would have to say that i have not had a belt failure cause damage to the chain or tensioner. A tensioner or bad pulley will cause a belt to fail, but not the other way around. I have however had several of the timing belt idler pulleys fail and cause noises.

Many times this is the cause for the timing belt to fail. Spin each of the idler pulleys to listen for a noise. Of course this would require removing the belt again. You could also use a small pry bar to see if pulleys have any play or seem to wobble. This can be done with belt still on. If any excessive movement, replace it.