It is an 89 model 740 GL, stock 4-cyl engine, 230K miles on original engine. The harmonic balancer (or crankshaft pulley) that drives all of the accessories failed. The outer part separated from the inner part. The outer part was turned at an angle of more or less 30 degrees by one of the belts, and it and the belts "jammed" up while the engine continued running for a while, the inner part of the balancer still locked on to the shaft, still spinning. Nothing was left of the rubber, and part of the bottom of the timing belt housing was ground away. Fortunately my wife noticed the overheat and stopped the car before the engine was burned up. Trying to save some bucks (money very tight) I went and bought a used harmonic balancer and installed it. However, it had quite a bit of wobble when I test-ran it, the wobble of a pulley running on a bent shaft. This of course makes the belts vibrate/jump. They are not jumping around so badly that you hear anything abnormal or feel any abnormal vibration when driving....but it looks bad, for sure. Well, I concluded that either I got a bad part, or the shaft end was bent by the extreme sideways pull that must have occurred when the outer part of the balancer got wedged/jammed up. So I spent $120 for a brand new pulley/balancer and installed it. Very bad news....the new one has *exactly* the same wobble as the old one did. Well, the car is actually my brothers', and when he got back in town and needed to drive it for a while, he took it to some mechanic who tells him that the balancer is not put on right and that is why it is wobbling....and says don't drive it at all, it is going to fail and ruin the engine. (We've probably put at least 2000 miles on it with it wobbling!) Now I would hope that he is right---I didn't install it right....but then again, someone who doesn't really KNOW that it is not installed right would certainly look at that wobbling harmonic balancer and conclude it is not put on right. But I cannot think of any way I could have put it on that would make it wobble. I mean, it was hard to get it started on the shaft because the tolerances are *very* close, and it is pushed ALL the way on to the shaft. I could not see or feel any erosion or damage to the shaft at all. The key has it securely locked in place, it's not coming loose. What could I have done wrong? And two different balancers have the same wobble? Its not a "run-out" wobble, it is a lateral wobble, as you would have from a slightly bent shaft. If the shaft end coming out of the block (which I guess is the actual end of the crankshaft, through the front seal?) has been bent a little, then there is nothing to do but a major overhaul to replace or true up the crank, right? If I take the balancer and belts back off, and somehow affix something like a metal ruler to the front of the engine so that it is almost touching the shaft--- then turn over the engine, would this be a good way to confirm a bent shaft? (don't know how practical this would be, as it might shake a lot). I'm getting the car back for some months or maybe permanently....just don't know if we should not drive it at all as that mechanic said....but there is no money for a crankshaft repair, and won't be for a LONG while, and we need to drive is on rare occasions for short distances, as a back-up car. I don't know of any mechanic I can take it to for diagnosis that I can trust....would like the opinion of someone like a pro who knows these engines. Thanks!
- posted
19 years ago