997 Suspension Creaking / knocking noise

Dosthilldave · Friday at 1:17 PM

I’ve just completed a “mild” suspension refresh on my 2005 C2S cabrio. New front shocks, top mounts (re used bearings) rear top mount bush ( previous owner had recently replaced shocks but reused very worn bush). Drop links all around and rear arb bushes. This work has removed any knocking or crashing of the suspension and after alignment, handling, steering and ride is vastly improved, I’m delighted with the result.

I am now getting to some of the lesser noises and I have one that I can’t pinpoint. It’s a light knock / rattle / creak that seems to be drivers side, but not sure front or rear. It is audible from the absolute lowest speeds, and not necessarily linked to bumps in the road. It’s not speed dependant nor related to drive take up. It’s not a constant noise, nor at all cyclical. It sounds a bit like muffled snooker balls knocking together. On the road, there is no suspension noise and likely this noise is drowned by road noise above 20-25mph

I’m pretty sure I’ve torqued everything correctly. Any suggestions where to look? Coffin arms and tuning forks looked ok, but they are probably original and the car has done 78,000 miles

911UK · Friday at 1:28 PM

there should not be any light knock or rattle if you've done this work, something needs rechecking

Dosthilldave · Friday at 1:30 PM

Pretty sure it was there before work done

photek · Friday at 2:01 PM

You've done so much already, just replace the original coffin arms and tuning forks as well - the noise is probably the ball joint in the coffin arm.

Unrelated to noises from the front end, but also check the engine and gearbox mounts - they can also effect the handling.

Dosthilldave · Friday at 2:22 PM

photek said:
You've done so much already, just replace the original coffin arms and tuning forks as well - the noise is probably the ball joint in the coffin arm.

Unrelated to noises from the front end, but also check the engine and gearbox mounts - they can also effect the handling.

That was what I was wondering. Engine mounts have also been replaced same time, forgot to mention that, again, big improvement over old ones

drmark · Friday at 2:49 PM

photek said:
You've done so much already, just replace the original coffin arms and tuning forks as well - the noise is probably the ball joint in the coffin arm.

Unrelated to noises from the front end, but also check the engine and gearbox mounts - they can also effect the handling.

This. The classic symptom is "snooker balls in a box". Most noticeable at low speeds over rough surfaces, particularly when heading downhill if at the front, and typically worse when the car is warm / hot (the ball joint and arm expand at different rates).
Don't ask me how I know

(I am on my 3rd set in 75,000 miles, and you can't really tell by looking but the play is very evident once you remove them).

Neven · Friday at 3:42 PM

As per @photek and @drmark

The noises you're experiencing are almost certainly related to the lower arms, specifically:

Snooker ball noise and creaking = coffin arms
Rattling = diagonal control arms

You have those on both the front and rear. Try and isolate to which end the noise is coming from and replace those. It recommended to replace both sides at the same time ideally. Or alternatively replace them all (front and rear) and have done with it.

Dosthilldave · Friday at 5:40 PM

Thanks guys, quite emphatic then. I’ll now have to start planning the next phase of the project.

Simple enough to do on the drive?

Neven · Friday at 6:59 PM

Dosthilldave said:
Thanks guys, quite emphatic then. I’ll now have to start planning the next phase of the project.

Simple enough to do on the drive?

Well it depends...

If the bolts come out without too much of a problem, then you should be able to do on the drive. Just remember you'll need to get a geo done once you've replaced the arms. You'll also need a separator tool for the ball joint.

However, if the bolts are seized (highly likely), then you may need to cut them out which is a hell of a job as you'll need to be very precise with a reciprocating saw - slip and it could cause carnage. You might be fine with doing this yourself, but personally that's a job way beyond me.

Giff · Saturday at 9:05 AM

Coffin arm replacement with seized bolts.

It’s actually not too bad with a reciprocating saw (can be easily done on driveway) and with a 150mm blade you’re not going to have to be too careful not to cause any collateral damage.

Cheap but effective kit:

Screwfix saw - https://www.screwfix.com/p/titan-ttb881rsp-850w-electric-reciprocating-saw-240v/282vv

Blades - you’ll get through a few of these - https://www.screwfix.com/p/bosch-s922ef-metal-reciprocating-saw-blades-150mm-5-pack/62700

Adjust the saw stop so the range of movement of the blade avoids contact with the subframe, saw slowly, too fast and the blade will overheat, sit there for a few mins with it cutting and job done.