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Re: rather nasty Serpentine belt idler pulley failure story Posted by Ari [Email]  (#2847) [Profile/Gallery]
(more from Ari) on Mon, 2 Jul 2007 12:41:21
In Reply to: rather nasty Serpentine belt idler pulley failure story, Rolf Karlstad, Sat, 30 Jun 2007 22:25:50 Members do not see ads below this line. - Help Keep This Site Online - Signup |
Yes, that belt can do a lot of damage thrashing around in there. And although a metal washer is a nice idea, sealed bearings fail when sealed bearings decide to fail. As a rule, I replace the idler and tensioner pulleys every 60K, with the belts every 30K. That is excessive, but I don't trust the pulleys to 90K.
How to get the rubber cover back on? It is a bit of a squid-wrestle, and best done with the liner off. But it can be done with the liner in place. Feed the nib of one of the rubber bits through the proper hole, and grab the end with a pliers. Pull directly away from the surface, so the nib stretches (and thins). Pops in. Feed in the next, and keep going.
In later years, Saab moved the pickup to the engine block, reading right off the crank, and away from the pulley. Why did Saab put it on the main pulley? Because Saab used pretty much the same engine in a lot of cars, and didn't make a lot of changes over the years. By putting the sensor on the main pulley, they could have the same basic block, head, and valve train for both DI and non-DI cars, depending on the market. Just don't install the distributor and put a plug into the valve cover. Could they have put the sensor where the distributor was? Sure. But that would require its own special rotating claptrap. The belt did make a mess of the apeture wheel, but that really is quite rare - otherwise, it is a nice, protected location, where the sensor can be mounted securely and accurately. Sticking in a surrogate distributor wouldn't have been as easy.
And face it, engines aren't really designed to reduce secondary damage - damage caused by an otherwise minor failure. For performance reasons, Saab and many others use an interference engine. Break a chain (worse - break a belt!) and the engine is trashed. Car engines have no oil-out operation - the ability to run for a little bit with no oil pressure. You'll see that in aircraft engines (inverted flight, and just very expensive engines). Adding that kind of protection either adds weight, cost, or impacts performance. Such is life. Cars are made to break.
Congrats on getting the car back on the road under dire conditions. The last time I lost a belt, I was all of 3 miles from home and toolbox. Coasting to a stop in the middle of Wyoming must have caused much sphincter tightening.
posted by 192.249....
, Mon, 2 Jul 2007 12:41:21 <-- Viewing This Message
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