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Last weekend in the house before going out of town again on extended business Monday morning, I want to get the 94cs turbo ready for another attempt to NJ State inspection just to buy 45 days more time so it won't get ticketed again for expired inspection when wife drives it around town. The car failed emissions and has a related, I believe, persistent check engine light. Tonight I want to crimp the wires of the generic O2 sensor I installed. But that's not what I am writing about.
Something else caught my eyes as I look into the engine compartment. The top bolt of the serpentine belt tensioner is sticking out, loose. Okay... I have no choice but to jack the car up, remove the front passenger side wheel liner to see what happened. Turned out the top tensioner bolt was sheared off, broken. I can remove the bolt head by hand. The only reason the s-belt is still tout is because the threaded in front part of the broken bolt sticks out about mid-way inside the tensioner top hole, holding it. It is only a matter of time before the belt comes loose, taking whatever in its way with it. I was lucky to have spotted it with the car in my own garage.
When the same symptom happened to my other 94cs almost two years ago. I thought my repeated clamping on the tensioner to remove and install did it. Now this same thing happened to another 94cs turbo which I just got in October, I am not so sure. Looking at the construction of the tensioner. I noticed the top attachment to the engine block has a slightly longer moment arm. The 8mm bolt naturally experiences larger bending moment than the bottom one. Although I have no information on how much force is exerted by the tensioner. I suspect the bolt may not have been designed to sustain the life cycle expected in such environment. Fortunately I have exactly the same size bolt in a box which hold various parts of the carcass of a previous engine.
I know this question only those DIY can answer. How many of you have had the tensioner top bolt sheared off?
Now I have a pair of sheared 8mm x ~2inch bolts in my garage. I am reasonably certain the broken bolt shank surface will be the kind typical of fatigue failures. However, only a metallurgical examination will accertain it. I just hope SAAB pay more attention to this in the next version of tensioner for the s-belt.
posted by 68.38.92...
, Sat, 1 Feb 2003 10:30:46, Sun, 2 Feb 2003 12:02:44
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