Ivan J

I recently had the PSS10 kit installed, with ride height set for ROW Sport. At the same time, one of the rear control arms was replaced on both sides (993 331 045 03). The rear suspension has started making a "groaning" noise on the drivers side when I drive over speed-bumps or things like the transition from street to driveway. The sounds seems to be consistent with what I would expect from a bushing that is worn out or binding.

Is there a most likely suspect based on what tends to wear out first?

Does it make sense to take an incremental approach, to spread out the damage to my wallet? Obviously this would be a bad idea if an alignment is required at each increment. Are there any rear bushings that can be replaced without needing to re-align everything?

JB 911

I would ask the person who did the install to check it over for you. Could be simple like something didn't get torques down correctly.

mpruden

Could be a simple as a sway bar bushing making noise. No need to align after cleaning or replacing it.

Did the sound correspond to a change in temperature or humidity?

bcameron59

This.

Garth S

Always direct your first suspicion on what was last changed ...

- verify that the bar drop links are vertical w. suspension at normal compression: correct by releasing the strut perch lockring & rotate as req,d - if necessary. If no hoist available, set rear corner on jackstand and jack under the hub to just lift ( by a mm or so) the car which =~ loaded weight.

- possible that the bushing ends of the new camber links were torqued w. suspension at full droop - far better IMHO to assure they are torqued at normal ride height ( as above) - easy to check, loosen bushing through bolt & tighted w. compressed suspension. [ if not done this way, the bushing may fail prematurely].

Spyder_Man

I agree with others. Look at what's changed first. That said a little while after having my suspension overhauled I noticed an odd noise from the rear of my 993 especially when braking and heading downhill. It was hard to place, but it turned out to be the rear inner CV joints drying out.

If the CV joints lose all of their grease it can lead to a very expensive fix because the entirety of both rear axles has to be replaced. My mechanic was able to fix my problem by injecting fresh CV joint grease into the joint with a custom-build long-tipped syringe.

Again as others advise, look at what has changed first. Next look at what might be impacted by the recent improvements and firmness added by the upgraded suspension. Lastly, double check the last time your CV joints were greased. (There is a reason why Porsche lists this as part of its recommended periodic maintenance routine.)

Good luck!

Ivan J

Thanks for all of the suggestions...

The drop links appear to be oriented correctly.

The suspension was pre-loaded before the control arms were torqued down.

The sway bar bushings appear to be fine, in that they are intact (for whatever that is worth).


The shop went over the car again. They re-checked the alignment, and re-torqued all of the points that they thought might be of concern. The groaning noise remains.

The shop thinks that the noise may be caused by the old bushings now being forced into a new working position as a result of the new ride height. Presumably, this would introducing different stresses in bushings that have been essentially pre-formed by the prior ride height. This sounds plausible to me; but, I'm not very knowledgeable about the 993 suspension. For those of you with a lot of suspension knowledge, does this sound plausible?

For now, I can live with the noise. It is only audible when I'm driving slowly in/out of parking lots or over speed-bumps.

bcameron59

Good to hear the drop links are lined up right and the control arms weren't torqued at droop - which should alleviate any stress on the rubber bushings. In any case I'd be surprised if there was a big enough change in angle from US to ROW height to stress rubber bushings enough to groan like that. Mine certainly did not when I went to ROW M030.

I would still try lubing the sway bar bushings with silicone grease, they can be especially noisy when it's been rainy and it's starting to dry out. This has been the source of similar groaning noises in six cars I've owned over the years, including 2 porsches, 3 volvos and one VW. Plus it's a very cheap & easy DIY.

k722070

this is just garbage to get rid of the customer.
you should be worried they are not interested in diagnosing the noise.
disconnect the rear sway bar from the drop link, takes 60 seconds, and see if the noise stops.
you will either eliminate a potential source of the problem or know if its the problem.

Ivan J

It looks easy enough to disconnect the sway bar from the droplinks. Is it OK to drive the car with the sway bar disconnected but still held in place by the two clamps?

OverBoosted28

Yes it's fine to disconnect it. Just remove the rear drop links btwn the perch and the sway bar. What you'll have is more body roll than with it connected. If noise is gone then it's most likely the sway bar bushings at the two clamps.

Don't know about "60 seconds". It might take 300 seconds :-)

Ivan J

The sway bar has been ruled out, that would have been too easy.

Visited the shop that installed the PSS10s and did the alignment. Using a stethoscope while bouncing the suspension, we could determine that it has to be one of the control arms on the left side. Its hard to pinpoint the source, because you can hear the sound no matter where you place the probe. I think that the sound is marginally loudest when probing the lower arm that is closest to the rear of the car (pardon my ignorance, I don't know the name or function of this arm).

Given the uncertainty about the source, they are going to disassemble all of the control arm connections on the left side, inspect, reassemble with some sort of suspension lube (lithium grease?), and redo the alignment.

Texas993

I had a similar noise after installing my PSS10 myself. The noise got progressively worse.

Turns out the dumb-*** mechanic (me) didn't install it properly. At the top of the strut, the cap is re-used from the original set up. I did not remove some rubber and plastic parts that the old spring would sit in. Leaving this in caused the new spring to be crooked, causing some rubbing. I had to remove the struts, remove the rubber/plastic pieces and reinstall the rear suspension. Also had to reset height and re-align.

I hope that they didn't make the same mistake.

See pics below for the improperly installed strut and the corrected set up.

k722070

ask them to take pictures of where they use suspension lube.
be interesting for me to learn where the grease fittings are on a 993.
the shop should disconnect the strut at the wheel carrier, put a bolt through the toe arm and move the carrier up and down.
this could produce a false negative because there isn't any weight on the control arms, but it is an easy test.

texas993's comment is a good place to look. the bilstein instructions aren't very clear and if this was the first time for the shop they could have assembled incorrectly.

Ivan J

No need to be sarcastic about suspension lube. I assume that they must have something in mind in terms of what might benefit from lubrication when they reassemble. I know that there is a TSB from Porsche about using lube on the sway bar bushings, perhaps there are other applications?

I'll mention the top-mount. They have installed PSS10s before, so I doubt this is the problem. Believe it or not, I'm working with a well-known and often recommended shop.