wbrian63

I'm hoping that maybe someone will have the same issue as I'm facing.

2002 S55 - 154k miles.

On the freeway or on surface streets if you cross a large tar strip or pavement drop/rise there's a definite thump under the car.

It seems to be coming from behind the driver's seat under the rear floor boards.

Just replaced the rear ABC valve and all the accumulators (pressure spheres). Both front & rear sphere were completely toast (filled with fluid).

Prior to replacing the rear valve I was getting a red light on the cluster when I hit dips or rises that caused the rear suspension to travel a lot - not any more after the valve replacement.

When I pulled the spheres and saw they were full of fluid, I assumed the thumping was coming from the ABC pressure lines whenever the suspension took a jolt - without the sphere helping to dampen the pressure spike, something's gotta give. No joy - bump still present.

Just replaced the driveshaft center bearing & support so the rear 1/2 of the exhaust was out and there was no evidence of the system banging or touching the body anywhere.

Transmission mount is new. So are the engine mounts.

Car doesn't eat rear tires, so I'm assuming that the issue isn't a worn suspension link or something in the rear. I've checked the suspension visually and I see nothing out of the ordinary.

One thing I did notice when I replaced the front control arms and lower ball joints was the struts detatch from the upper mounts when the suspension hangs free. If I go over a parking lot bump too fast I hear a definite thunk in the front which I assume is the strut pulling free of the mount as the tire drops over the bump before the car can follow. If I go more slowly, the noise doesn't occur.

I wonder if the same thing is happening in the rear with the struts.

The mounts aren't sold as a separate part, so the only repair is new $trut$ which is not really necessary - I just take care to avoid causing any suspension travel that might allow the strut to drop free of the body even a little bit.

Any ideas would be appreciated.

Regards

mrbenzes

Id say you hit the nail on the head about the top of the struts not connected at the rear....
Mike

wbrian63

Kinda the car-equivalent of a Sherlock Holmes phrase: once you've eliminated everything that can't be causing the bump, what remains must be what is causing the bump...

I worked for a company years ago that made exotic gaskets for the chemical industry here in Tx. They had some really odd stuff - in some cases involving rubber bonded to metal.

I'm going to tap one of those resources and see about re-bonding the struts to the mounts. I'll bet there's an adhesive out there that can take the stresses.

Anyone have any other ideas about where the bump could be coming from?

mrbenzes

Haha, maybe if you bought the car used, a smuggler left a big bundle of cash in between the trunk and gas tank and it is loose in there...just awaiting discovery..I'd say $50K in 20 dollar bills would make a bit of a thump...

perfota

Hi, look like I am going down the same path with the noise issues. I was curious to see of you had found a solution to your noise? I can't seem to find where the clunk noise come from on my car, but definitely has some clunk noise over the back area.
Thanks
Ciao
Perfota