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Harmonic balancer? Posted by Ari [Email]  (#2847) [Profile/Gallery]
(more from Ari) on Wed, 4 Jan 2006 11:57:37
In Reply to: Clanking noise on the engine, Oni, Wed, 4 Jan 2006 09:21:43 Members do not see ads below this line. - Help Keep This Site Online - Signup |
If the sound is a rattle, high up on the engine, that would be valve noise as the oil pressure comes up. Usually normal on a Saab engine, but it might be an indication of low oil pressure. If you suspect low oil pressure for any reason (oil light flickering at idle, when the car is warm), get the oil pressure checked.
If the noise is lower down on the engine, then it may be belt/pulley related. The one that comes to mind is the Harmonic balancer, also known as the main pulley. The big one on the bottom. It is a sandwich of an inner and outer pulley, with rubber in the middle. The rubber fails over time, and when the car is cold, the outer portion doesn't rotate with the inner portion. This makes all sorts of interesting noises. As the friction causes the assembly to warm up, it sticks better. A harmonic balancer failure is a bad thing - They don't heal. If the pulley walks off the front, the belt will come off and do some damage. If the pulley walks off the back, it runs into the oil pump, and starts grinding through it.
I would have someone start the car, cold, while you listen at the engine with the hood open. Try to get a better idea of the noise and where it comes from. Also, use a flashlight to look at the belt and it runs on the pulleys - especially the tensioner pulley, a black pulley behind the AC compressor. The belt should be running in the center of the pulley. If it's running off to one side, that can be a sign that the harmonic balancer has shifted. The tensioner pulley should 'jiggle' a little - maybe 1/8 inch or so. If it's bouncing around, that can be a bad tensioner shock or other pulley problem.
The best check of the harmonic balancer is to draw a chalk line or two (I also use liquid white-out) across the face of the pulley, at the ede. Then start the car a few times. See if the lines still line up. If the inner and outer parts have shifted, the pulley needs to be replaced. I just mark the pulley and monitor it.
posted by 192.249....
, Wed, 4 Jan 2006 11:57:37 <-- Viewing This Message
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