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Registered
Join Date: Sep 2007
Location: Ottawa, ON, Canada
Posts: 113
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Help diagnosing intermitent clacking noise (center front).
Car is an 89 3.2 w/ 88,000 miles. Stock engine and muffler. I don't believe the engine has ever been out. In the last 500 miles it's had a new rotor/distributor cap, fan belt, plugs and valve adjustment. The valve train has a nice sewing machine sound. Oil level and pressure is good. SW chip.
In the last 100 miles, I've experienced 2 occasions were I started the engine and could hear a clacking or toc-toc-toc sound. Sticking my head in the engine bay and reving the engine, the clacking speed increases with revs and seems to be coming from the alternator/fan shroud and or rear of fan area (center front of the engine). I checked the fan shroud if there was any "scraping" going on from the fan blades but saw nothing. A good test would be to disconnect the fan belt when the sound is produced, but the unfortunate part is that in BOTH instances that this has occurred, shutting down the engine and restarting it made the clacking (toc-toc) go away. Could this be rod knock? Chain tensioners? Alternator bearing? I'd really like to eliminate the chances of it being rod knock or chains! Best regards, Initial
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95 Carrera 4 Black/Black Coupe, Row M030, Bilstein HD Past - 89 911 3.2 silver cab |
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07-20-2009, 06:31 AM
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muck-raker
Join Date: Jan 2009
Location: Coastal PNW
Posts: 3,059
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If the fan belt was recently replaced, check the belt tension to make sure there is enough play. If overtightened, it will screw your alternator bearing. This will sometimes create a similar noise.
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STONE '88 Cabriolet, using EP Slick 20w50 partial synthetic Snake Oil...just as Rommel intended.  Deny Everything; Admit Nothing; and Always Make Counter-accusations 
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07-20-2009, 10:38 AM
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Registered
Join Date: Sep 2007
Location: Ottawa, ON, Canada
Posts: 113
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Good advise. I went ahead and moved a shim from front to back. I previously had about 1/4 to 1/2 inch of deflection, I now have a solid 1/2 inch of deflection.
Took the car for a nice top down spin with the much looser fan belt and everything seems fine. I can only wait and see if it happens again.
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95 Carrera 4 Black/Black Coupe, Row M030, Bilstein HD Past - 89 911 3.2 silver cab |
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07-20-2009, 04:50 PM
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Registered
Join Date: Dec 2004
Location: San Diego
Posts: 121
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Also check the outer alternator/fan drive pulley half very closely for cracks connectiong the small holes surrounding the main shaft hole. Mine was cracked through about 5 holes and sounded like a rod knock. Very hard to see.
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72 T 3.2 |
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07-21-2009, 04:20 AM
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