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Old 07-29-2012, 08:59 AM   #1
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Knock noise from behind rear wall

Have had a 2002 S 3.2. At around 20,000 kms. in odometer subtle knocking noise began at wall behind seats, while particularly going over cobble-paved roads after a 10 or 15 minute warm-up. At times it also looked as coming from doors, or seat belts, or engine, or...

Turned out to be faulty rear suspension trailing arms (parts no. 986-331-143-4 or 043-7). The ball-joint cap looses with time and as grease inside gets hot and thin, ball-joint knocks and transmit noise to the wall where they're attached. More easily reproduced when lifting accelerator pedal, going slow. Can be first at right or left side, but with time problem goes to both.

Lots of chassis hearing tests before finding it. Hope this helps.
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Old 10-12-2012, 07:35 AM   #2
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Exactly symptoms of mine, will have a look at joints.
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Old 10-12-2012, 08:25 AM   #3
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Originally Posted by josefer View Post
Have had a 2002 S 3.2. At around 20,000 kms. in odometer subtle knocking noise began at wall behind seats, while particularly going over cobble-paved roads after a 10 or 15 minute warm-up. At times it also looked as coming from doors, or seat belts, or engine, or...

Turned out to be faulty rear suspension trailing arms (parts no. 986-331-143-4 or 043-7). The ball-joint cap looses with time and as grease inside gets hot and thin, ball-joint knocks and transmit noise to the wall where they're attached. More easily reproduced when lifting accelerator pedal, going slow. Can be first at right or left side, but with time problem goes to both.

Lots of chassis hearing tests before finding it. Hope this helps.
Ditto here on the noise! Had similar noises…turned out to be a front engine mount. It was not yet "sloppy" but going there very fast. The rubber had torn and then vulcanized, so there were a couple chunks of rubber holding it in.

I go down dirts roads to find houses (I know it should be a crime, in a Porsche, but what's worse is these people are paying tons of property taxes to the county for roads and bridges….and all they are getting is a dirt road).

Anyway, while my car was "in the air" getting the front mount installed, I hit the joints with WD-40 using a syringe - as some members have suggested - and PRESTO! My car rides like a dream, no noises, faster acceleration - not sure how THAT's possible-maybe the motor mount, something to do with the engine transferring torque more effectively or something like that. At ANY rate, DO IT!

Grab a syringe and spray the WD-40 in a cap, suck it out with the needle. We have left over needles from giving dog shots.

You want to "pierce" the boot over the joints near the top or look for a BULGE and hit it there so you do not hit metal! It took an average of TWO (2) 3cc syringes per wheel. NOTE: Having car in the air may have allowed me to shoe-horn more WD-40 in there. The results were surprising!

Hope that helps.
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Old 10-12-2012, 11:35 AM   #4
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Originally Posted by josefer View Post
Have had a 2002 S 3.2. At around 20,000 kms. in odometer subtle knocking noise began at wall behind seats, while particularly going over cobble-paved roads after a 10 or 15 minute warm-up. At times it also looked as coming from doors, or seat belts, or engine, or...

Turned out to be faulty rear suspension trailing arms (parts no. 986-331-143-4 or 043-7). The ball-joint cap looses with time and as grease inside gets hot and thin, ball-joint knocks and transmit noise to the wall where they're attached. More easily reproduced when lifting accelerator pedal, going slow. Can be first at right or left side, but with time problem goes to both.

Lots of chassis hearing tests before finding it. Hope this helps.
I had the same problem, and had my Indy replaced the one on the passenger side. He had a heck of a time determining what it was, but sounds good now, just like it should, no knocking.

Just wondering, what did the replacement arm cost you? I saw them on Pelican for $116.00, but mine was three times that. I guess it's because he ordered a genuine replacement? The number on the arm didn't match the replacement on Pelican.

I also had a manifold leak welded on one side, now it really sounds cool!
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Old 10-12-2012, 04:19 PM   #5
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Originally Posted by mistermac99 View Post
I had the same problem, and had my Indy replaced the one on the passenger side. He had a heck of a time determining what it was, but sounds good now, just like it should, no knocking.

Just wondering, what did the replacement arm cost you? I saw them on Pelican for $116.00, but mine was three times that. I guess it's because he ordered a genuine replacement? The number on the arm didn't match the replacement on Pelican.

I also had a manifold leak welded on one side, now it really sounds cool!
The $116 part is a front control arm, not a rear, so that's one reason.
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