Knocking noise from back of car

sbloxxy · Jun 11, 2007

Hi all, I've got an annoying (to say the least) rattle/knock from somewhere on the o/s rear. So far I have replaced the nuts holding the exhaust heat shields in place, I have replaced the disc brake inner shield, replaced/tightened various exhaust clamps and brackets - but its still there. Its worse over rough roads and I'm now thinking it may be a suspension component. To help point me in the right direction, has anyone else suffered from this one or got any ideas? My car is a 2000 Boxster S, by the way.

channella · Jun 12, 2007

I'd think suspension strut first Maybe trailing arm second.

Guest · Jun 18, 2007

Hi sbloxxy

Does your knocking happen when you go over speed bumps?? If it sounds like your exhaust is loose, then I had the same problem and both the suspension arms needed replacing. I got it done at my Indi for around £450... All OK now.

RPEE · Jun 25, 2007

You didn't say what the sound was like. I had an annoying rattle in the rear that sounded like i had some loose blocks of wood in the boot. It was really evident going really slow on bumpy surfaces. Finally tracked it to the stiffening boards under the boot carpet. A few well placed sticky pads did the trick. My local indie suggested replacing the rear transverse control arms. Glad i didn't. Open the boot and knock on the floor and see if the sound is familiar, worth a try.

Guest · Jul 1, 2007

This sounds just like a problem I recently had and I agree its very annoying. The noise was cured by replacement of both rear suspension trailing arms. Apparently the bushes wear out at the forward attachment points. The work was done by OPC Leeds and they quoted £500 to replace.
The worrying thing though was that my Nov 2003 3.2 S had only done 15000 when the noise developed and was still within its 1 year Porsche Approved used warranty. I argued that this should be a warranty job in view of the very low mileage, but the OPC at Leeds said it was wear and tear and that this was not covered under the warranty. Wear and tear after 15K?? So I complained to Porsche UK and got the cost reduced to £125. The noise has gone and the handling has improved noticeably !
I asked Porsche UK if this was a common problem with all Boxsters, they couldnt really explain it, but did suggest that the previous owner might have lived in an area where there was a lot of cobbed roads. I think its more likely to be something to do with the colour of the car which is Arctic Silver.

Good luck in getting your problem solved.

Black80XSA · Jul 1, 2007

If its a definite clonk when traversing entry/exit ramps across pavements and onto garage forecourts then its likely to be the trailing arms.

sbloxxy · Jul 6, 2007

I've been grovelling around under the car (again) and have checked every bush/joint for play - nothing appears to be worn or to be moving excessively. Obviously its worse on rough roads but I also noticed that if you throw the car about from side to side when driving (don't ask me how I discovered this!) its also very noticeable. I still think its suspension related but I'm out of ideas. A couple of you mentioned rear suspension trailing arms: are these the ones that lead forward from the rear suspension, mounting on a point high (ish) up on the bodywork?

cotty · Jul 22, 2007

I have a 2001 'S' and I had a very similar problem last year. Knocking behind the passenger compartment when going over speed bumps, bumps in the road or pot holes. I soon noticed that the knocking reduced massively if I was accelerating. Once I eased off the accelerator the knocking came back. I took the car to my local independant, Ninemeister in Warrington, and explained my theory of less knocking during acceleration. They were confident they knew what it was.

A day at the garage and 2 new rear control arms later, the knocking was gone. It cost me £500. Not cheap but now any passengers don't think the car is falling apart.

Hope this helps.

Cotty

RPEE · Jul 23, 2007

Hi Cotty,

Which control arms, the transverse ones (long fork like) or the coffin shaped ones from the hub to the body.

RPEE

cotty · Jul 24, 2007

RPEE,

To be honest I did not check. But fortunately I have the part number, 98633104307 and a quick search on
http://www.design911.co.uk/index.htm?Region=UK
shows it to be the fork like ones.

The guy at Ninemeister told me that bush wear on this part is commom on the Boxster. The reason why the noise reduced under acceleration is due to the arms pushing from the rear wheels on to the engine bay. This reduces the amount of movement in the joint which leads to less noise. Sounded plausible and it did work!!

Hope this helps.

Cotty

sbloxxy · Sep 7, 2007

Finally sorted this one out: it was the rear anti-roll bar bushes. Worn to the point that they are allowing the anti roll bar to knock slightly.
I can't tell you how fantastic it is to finally get rid of the problem and be able to enjoy a 'quiet' car again...

Helen Goff · Sep 7, 2007

ORIGINAL: Black80XSA

If its a definite clonk when traversing entry/exit ramps across pavements and onto garage forecourts

i had that sort of noise on my 2.7 and we tracked it down to the exhaust heat sheild a couple of clips had fallen off. think it cost me about £8 for replacments.