I just bought a 92 740 Wagon (non turbo automatic)139k miles, with unknown service history.
The timing belt cover was loose and when I removed it to inspect the belt the cover sort of fell apart and I found the belt was only about 1/2 inch wide and was partially riding off the front of the pulleys. I know this is not good.
Questions before I change belt:

Why did it ride off the front of the pulleys?
Is this a symtom of a bad tensioner or just too long of a service interval?
I thought belts just break teeth and shred when they fail.

I have an impact wrench to remove the balancer, but how can I be sure the torque is correct when I put it back together? Can it be too tight? can I damage anything by over tightening it?

Thank you

Hi George,

I think success tightening with an impact wrench depends a lot on experience. There are two methods for holding the crank while you use a torque wrench: a $50+ tool or two feet of clothesline to block the cylinder. I use the rope. If you search you'll find a good procedure written by Lucid. There are pitfalls to using an impact wrench others have run into, but mostly bonehead errors like tightening with the key out of place.

The tensioner is the suspect in the belt riding off center. Any timing belts that have failed for me have been stripped teeth at the crank sprocket, with a leaky cam and/or crank seal to blame for the lack of longevity.

BTW, on the bogging problem, I just gave my daughter's secondary ignition a bath in the dishwasher after noting I could make the problem appear with the hose nozzle turned on "mist" setting. She said it wouldn't pull out into traffic when it was raining pretty hard. Now I am repeating the misting, and not experiencing the bog while twisting the throttle spool. Will get her a new set of wires, cap, and plugs anyway.
--
Art Benstein near Baltimore

The taste of low quality lingers long after the satisfaction of low price.

My thoughts.

The belt my be worn because the tensioner bearings have failed so badly that the Tensioner pulley was leaning causing the belt to rub. Or the Tensioner was not put on correctly at last Timing Belt change. There is a little tit in the back of the Tensioner assy that needs to fit in a hole in the Engine block. If it doesn't, it will angle the Pulley.

The Crank bolt should be Tight. They give a toque of 40 Ft lbs then 1/4 turn more. I bet that brings it up over 100 ft lbs. In MY opinion, this torque is not critical, you just want to make sure it doesn't loosen up for the next 50K miles. I use an Impact gun to take it off and put it back on. My gun has a few Settings. tight, tighter, real tight and F'n Tight. I set it to Real Tight and that works for me.


--
'75 Jeep CJ5 345Hp ChevyPwrd, two motorcycles, '85 Pickup: The '89 Volvo is the newest vehicle I own. it wasn't Volvos safety , it was Longevity that sold me http://home.lyse.net/brox/TonyPage4.html

Thanks, those were my thoughts on both the tensioner and impact wrench.
Service plate on timing cover indicates belt was changed @55k and now has 139K. So I guess the tensioner bearings just wore out.
George