PASM Shock absorber faults

[berty987]

I am wondering if anyone with a 997 has experienced a similar issue to my PASM equipped boxster. The car demonstrates a knocking sound from the rear when driving at low speed over rough surfaces when the car is cold or outside temperature below about 8 C. The sound is a clunking or vibration type sound similar to that when an exhaust hangar fails and the silencer thumps against the underside of the car. The Noise is reduced by setting the PASM to sport mode and seems to disappear completely after the car has been driven for about half an hour. The rear suspension has been checked and no signs of rear fork arm, or suspension pivot arm wear or damage. I seem to recall reading someone here had rear PASM shocks replaced, please can they elaborate on the symptoms and which dealership undertook the diagnosis. Thanks

 

[garyw]

Rob had his shocks replaced, I seem to remember the symptoms being handling issues rather than a noise from them..
I'm sure he'll catch up with this thread when he's not working.

garyw

 

[Geoff_Fields]

I'm sure I've read about similar noises before on this forum. Turned out to be attributed to the heat shields, which had corroded clips or something. So the shields vibrated when cold then shut up when warmed up.

 

[robert997]

Hi berty, I had rear damper failure, there was no noise, only poor handling and copious cork-screwing. Doesn't sound like the same thing as you.

None of the local (Midlands) OPC were interested or able to diagnose damper failure, beyond a quick drive. There have been other customers with worn PASM, one of whom owns an engineering firm. All customers have had to pay for replacements (wear and tear item even under new warranty) except the afformentioned chap who was able to test his own damper and prove a failure. He was then refunded the cost of one damper, even though he had to replace the pair, obviously.

The morale of this story is that the OPC's did not have appropriate equipment to measure/test/repair damper units, like many things a decline of engineering capability here as we migrate to a disposable culture I guess. No doubt it's cheaper for them too to make a straight-forward replacement rather than a refurb.

Chris Franklin at Center Gravity (sic) is the man who CAN diagnose damper issues, and has a contract with Bilstein (and KW ?) to refurb dampers. That is a far more cost-effective route !

Your noise could well be a damper problem, or perhaps a spring ? Broken springs are not unusual thanks to speed humps. PASM Dampers on the 997 they were in the regoin of £350 each corner plus VAT and many hours labour and alignment...Rob

 

[okellyt]

One of my PASM dampers has a slightly leaky strut so sometimes you can here a slight click if its worked hard.

Porsche, Porscheshop and Chirs (Centre gravity) have looked at it and said its fine, so I am leaving it be until it wears out.

Other than Robert I have not heard of any one else with problems on 997's[]

 

[berty987]

Thanks for the replies. I am sure its not heat shields as these have been checked under the service recall and also the sound is a low frequency knock/ clunk rather than a metallic rattle. I think I can also rule out the spring as the sound goes away after the car has warmed up. The idea of taking the car to a suspension specialist isn't something i had considered, though I would not want to spend 400 pounds on a geo session if the shock needed replacing. Warranty direct would be happy to pay for a replacement shock if it could be positively identified as causing the sound and proven to be faulty or defective. I seem to be at an impasse as without significant investigation (likely to cost hundreds) I cannot claim for the replacement or repair. Warranty direct will only support 1 hours worth of investigation so I am in somewhat of a cleft stick. I will give center gravity a call and see what they can offer. Thanks for the suggestions and feedback.

 

[Rodney Naghar]

Worn drop links make a knocking sound, they are cheap to replace and are quite a common problem. Take them car to an indi for a free investigation, it is very unlikely your suspension will have gone to that extent.

 

[Black80XSA]

drop links would be my first guess too - perhaps the engine/exhaust heat is expanding them sufficiently for any wear to be compensated for after a period.

 

[berty987]

Unfortunately the "guess" was incorrect, new drop links fitted along with anti roll bar bushes and no improvment. I've now contacted Chris at Center Gravity who has suggested I take the car to have the struts removed and sent to Bilstein for tests on a dynamic rig. Whilst the struts are removed the pivot arms and track control arms can be inspected and checked for signs of wear. I feel confident this approach will get me a definitive answer to the problem.

 

[johnk]

we currently have a cayman with said fault but coming from front and does point to the pasm shock but like you say it's an expensive do, are doing some more tests tomorrow so will keep you posted

 

[berty987]

Thanks John , please keep me updated on the progress. The car is booked in with Chris at Center Gravity , I will post the results of the tests in the next few days.

 

[berty987]

Quick update :

Car went into Center Gravity today and the rear shocks were removed and sent for testing at Bilstein. This is by no means a simple task as I was soon to find out. Basically the whole rear suspension , disk / caliper and hub assembly needs to be removed, then the damper dis assembled. Thankfully Chris Franklin is very experienced in doing this sort of work and made the whole process look routine. After the strut had been removed it was a process of dismantling to get back to just the damper , before Chris's wife drove them up to Bilstein for testing. I was very impressed with the quick turnaround at Bilstein and Center Gravity , due mainly to the excellent relationship that Center Gravity have with them , the Bilstein sfaff even staying late on a Friday afternoon to do the tests !!!.

The testing equipment at Bilstein seems second to none , each damper tested over a full range of loads and a bump and rebound plot produced as a result. The test results did in fact prove the rear dampers/ shocks were faulty as one had a particularly bad response whilst the other showed an almost inverse plot to what was the norm. Strangely enough one damper felt warm to the touch compared to the other when removed from the car , as it turned out the cooler of the two dampers was in fact in worse condition !

Whilst the dampers were being tested Chris took the time to talk through and demonstrate simple tests to prove the other suspension components were in good order. Having satisfied himself and myself that there were no issues with any of the bushings or ball joints the parts were cleaned and prepared ready for re assembly.

This may seem to some as an exhaustive and expensive length to go to , but having seen the damper plots I feel that it was time and money well spent especially as it gives more weight to my warranty claim to have the dampers replaced. I do not know of any Porsche specialist or Porsche center that has this facility to test dammpers , it also encouraging to see the time and care that Chris shows in resolving these sorts of issues for is clients.

For others with PASM equipped cars that may have been told by Porsche they dont go wrong , I think it also shows that PASM dampers can fail even on relatively low mileage cars , my car is just over 40k at the moment.

 

[spyderman]

This will be a good test for your warranty - they're not covered by Porsche - they consider shocks a "wear and tear" item.

 

[berty987]

I have already asked warranty direct what's covered under the luxury care policy and had confirmation the shocks are included. The battle has been proving they are defective, hopefully this work will provide the suitable evidence to allow them to proceed with the claim.

 

[berty987]

Waranty Direct have now agreed to repair the car , though the data from Bilstein suggests the sister shock has not failed , therefore cannot be replaced under the terms of the agreement. I need to think long and hard if I wish to pay out to have the other side replaced as "good practice" or accept that the tests show no defects to substantiate replacment. Though I have had to go to some rather extreme lengths to prove the shock was faulty, I have to praise warranty direct in their attitude and final decision on the claim. I am also hopeful that the additional investigative costs over and above the usual 1 hour stipulation will be paid.

For others looking at extended warranties I would suggest considering policies from Warranty Direct or others that cover wear and tear items , particularly if the car is equipped with PASM. I'm not sure about the other policies but the only downside with warranty direct is they will not cover vehicles that have been used for track days. In my case this was not an issue as the car is used for touring and weekends , for the more enthusiastic owner this may be an issue.

I will report back once the car has been repaired in a few weeks time.