Bill Ball

In the last 3 weeks my trusty S4 has developed a very odd clunk.

1. Sounds like something swinging freely and striking against the body with a definite non-metallic clunk.

2. Sometimes definitely sounds like from the front left wheel well; other times from the rear of the car. Passenger says it sounds like front right wheel well. I got inside all wheel wells, covers off, and found nothing loose.

3. A few times there has been NO CLUNK for 30 miles or so. Once it disappeared after filing the gas tank, so I thought it was something in the tank. I removed the level sender, which was in perfect condition, and could find nothing loose in the tank. The internal pump was solidly mounted and visible. THE TANK APPEARS TO HAVE A SECTION ABOVE THE FLOOR THROUGH WHICH THE SENDER STICKS. SO, SOMETHING COULD BE LOOSE UNDER THAT SHELF. ANY IDEAS? I probed around on the top of that shelf and found nothing loose.

4. Most apparent at slow speeds over even slightly uneven surfaces.

5. Can be brought on by moving the steering wheel back and forth sharply BUT ONLY while moving down the road. NO CLUNK when moving the steering wheel while the car is stationary. Wheel bearings are snug and quiet. Calipers tight. Tie rods and balljoints snug, ALTHOUGH there is slight movement in one tie rod inner joint, but no clunk when I exercise it.

6. No clunk on acceleration or deceleration (ruling out TT balancer).

I have inspected all the suspension and steering related bolts and bushings. All are tight and intact. Rear upper control arm bushings and from upper A-arms are relatively new. I once had the upper rear shock mount nuts come loose. That made a RATTLE rather than a banging clunk and was very easy to locate as coming from the rear hatch area.

I found one exhaust hanger rubber off. Reinstalled that - no change.

The clunk is getting more consistent, although occasionally I do not hear it at first for several miles. I've gone over the underside of the car and peered all over the engine compartment. I've check the battery box and the spare tire well.

IDEAS????

TIA.

John Speake

It certainly sounds like something loose in a body cavity. The light in my hatch fell apart and I haven't managed to get all the pieces out yet - the random rattling is very annoying !

Mrmerlin

is it possible the RR sway bar link is bent and rubbing or loose

bureau13

I have some mysterious sounds that come and go, sometimes manifesting in a semi-rhythmic clunk...I'm about 90% sure it's got something to do with the e-brake bits behind the passenger side rear rotor. It always sounded like the left side, and I thought it was the rear, but sometimes sounds can be deceiving, especially from the driver's seat.

Jetdriver69

I had a random clunk myself, but more of a rattle.

I put a Borla exhaust on with 285 rear tires and there is very space back there now.

If the mounting bolt below the rubber mount directly above the muffler is not super tight, the muffler can rub against the tire or the rear suspension.

I had to move the muffler a bit to the right and torque everything down and replace the worn rubber mount with a new one. Hopefully that will keep everything in place and solve the mystery noise problem.

If not, it is off to the sheet metal shop to fab a bracket to keep the muffler from migrating.

NC928S4

Slight adjustment to exhaust hanger brackets cleared up my clunk. The hanger hooks on the drivers side ( 928 111 264 01) and ( 928 111 260 00) were causing the intermediate silencer to bump on the body. The adjustment was very minor but got rid of the clunk.

hacker-pschorr

I had a similar sound when a CV joint was waving goodbye in my 944S. It was totally random but definitely a "clunk" sound. Sometimes resembling a cow bell.

dr bob

Did you put the bowling ball away after league last Friday?

chitown928s4

Check your steering rack bushing. While up in the air have someone else move the wheels up down sideways. Keep an eye on bushings.

SeanR

Pull the caps off the rear shop mounts (in the hatch behind the rear seats) and grab you a 19mm socket, see if you can turn it easy. If so, pull the 3 17mm nuts and the cover, counter hold the shock and tighten up the 19mm nut. I've seen this many times as people don't get those tightened enough and come loose over time.

Mongo

Sounds like a CV joint to me.

granprixweiss928

Perhaps a shock going bad. I had a bad one RF and it first seemed to be RR. It would make a clunk like you suggest. it would not do it in garage. only driving.

Bill Ball

Thanks for all the replies.

Steering rack is locked down - no bushings - and is very snug. And since the clunk does not happen except when the car is rolling, I essentially ruled out the steering rack.

Sway bars and links are all tight and intact. Same for every other suspension part.

No bowling ball.

Nothing loose in battery box or spare tire well.

I do have an axle with a torn boot. The joint does not have any wear play, but the shaft does move in and out more freely than it should due to some loss of grease. Going to remedy that tomorrow. It is true that the noise only happens when the car is rolling, so that would be consistent with a bad axle, although there is no noise at all unless the car is shaken. Rolling along on a smooth surface brings on no noise.

I can bang on and shake the exhaust and nothing clunks.

I've gone into all the wheel wells repeatedly looking for something loose. I tied down a few things more securely with no change.

I checked all the shock mounts. I suppose this could be a bad shock but the Bilsteins are not leaking nor does the car handle badly. No noise in turns or when accelerating or braking.

The gas tank is one mystery area. I was told there is a sump with a cover that can come loose, but I don't see one at least from the level sender port. I don't think there is a sump.

It sounds like something swinging randomly against a body panel and only occurs with jostling, not with acceleration or braking.

NC928S4

Not that I'll ever admit to doing this but any chance you left a socket, wrench or screw driver in a door panel?

Bill Ball

Well, the doors are pretty quiet when slammed. A dropped tool is a good possibility. I need help locating to source area. It's not clear if it is front, rear, left or right.