I have a nasty and untimely clunk

[benjj]

Some advice please gents. I've got to leave in the car for Goodwood in 24 hours so have tomorrow to try and square this away.

I have a nasty clunk coming from the rear half of the car.

It sounds like a metal on metal banging. It's like someone has left a pair of molegrips on the rear suspension and it's banging around. They haven't though, I've checked!

It is not speed/throttle/gearbox related. The sound happens when going over bumpy ground at all speeds. The sound stops when brakes are applied.

Things that have been replaced over the last 2 days:

Rear discs, pads and handbrake shoes
Rear halfshafts/seals
Rear dampers
Rear wheel bearings

The exhaust has also been checked from the manifold back and it's not fouling anywhere. Likewise we disconnected the rear ARB droplinks thinking it may be that. It wasn't.

The fact it stops when braking makes me think it must be brake related but it's had an MOT today which it sailed through with flying colours. Spot on brake balance and performance (as expected, all new components and racing blue fluid).

Anyone have any ideas? Surely applying the brakes and it stopping is significant but I'm having some serious brain fade now after mucking around with it all day when I should be working...

Ben

 

[sutters]

Cracked or broken spring possible?

 

[benjj]

Hmm, it's definitely coming from the back half of the car and there aren't too many springs back there!

Will give them a quick once over though just to be sure. Have a spare set so all good if one turns out to be fubar.

 

[944 man]

ORIGINAL: sutters

Cracked or broken spring possible?

The don't have 'springs'!

 

[944Fripp]

Just dealt with something similar.

Turned out it was the newly replaced pads rattling in the caliper.

Exactly the same symptoms as you describe (particularly the one about applying the brakes makes the sound go away).

The good news is that it was an easy fix (ground down a tiny bit of the metal part of the he pad so it fitted correctly in the caliper) and it was good as new. It's caused by slight oxidation on the aluminium caliper preventing it from sitting just right and can't be seen with a visual check. You need to take the rear pads out and check for fouling as they go in without the retaining clip.

Another option could be that the anti vibration pad on the back of the pad may not have been installed right...or at all....or may have fallen off.

Don't panic though, the car was perfectly safe without fixing this, just a bit noisy over bumps! []

Maybe my 944 will see yours at Goodwood....if I can get the new CV joints fitted in time!

 

[benjj]

Thanks Fripp. As you posted that I was on the phone to the bloke who runs my cars. He suggested that the sliding plate/nylon insert could be worn and causing the slip.

Either way I think we may have nailed it - sadly won't be done in time for Goodwood though so I'll just have to put up with it for the 500 mile round trip!

I'm at FoS all weekend with the charity I work for - Mission Motorsport. My car will be on the stand so if you see it come up and say hello and meet some of the lads.

Cheers,

Ben

 

[zcacogp]

I'd be with Tom in that it's brake related, particularly if the noise stops as soon as the brakes are applied. Ill-fitting pads are an option (yours is a lux, non, hence no Brembo calipers?)

Are you sure that the calipers are correctly mounted, and the mounting bolts done up tight?

Another diagnostic would be to induce the clunk noise (i.e drive over rough ground) and try slowing it down on the handbrake. This will cause similar reverse-loading of the drive system but not be related to the calipers. If this doesn't stop the clunk then it is (almost certainly) caliper related. If it does stop the clunk then it will be something else.

Let us know how you get on. I hope you make it to Goodwood OK.


Oli.

 

[benjj]

Yep, early steel single pot calipers all round on mine. Will make sure the caliper carrier bolts are all nipped up but pretty sure they are as they've just been off for the disc/pads/wheel bearing work.

Great idea with the handbrake - thanks, will do that tomorrow morning and see where it leads.

 

[944Fripp]

ORIGINAL: benjj

Yep, early steel single pot calipers all round on mine. Will make sure the caliper carrier bolts are all nipped up but pretty sure they are as they've just been off for the disc/pads/wheel bearing work.

Great idea with the handbrake - thanks, will do that tomorrow morning and see where it leads.

As I was posting my reply I did think "what if they're not Brembo brakes?". Still, either way the effect of braking is telling so it's got to be something around the caliper me thinks.

Good luck with it, I'm at FOS on Saturday so I'll pop over and say hi.