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Discussion Starter · #1 ·
Have had this problem from day 1, 5 years ago, when I picked up this SLK.
It has a rotation noise coming from the bottom and causes the BAS/ESP light to come on. It's been 5 years and I have been replacing almost everything I could think of but the problem just won't go away.

The noise starts from the moment the car starts to drive. It's a flapping noise that changes speed as the car go faster. It is highly correlated to the wheel speed. Car drives faster, noise goes faster.

I had owned another SLK 230 in perfect condition so I know how quiet the drivetrains, brakes, suspension and everything.

Over the 5 years I did everything I could to source the problem and end up with limited success.


List of things I have replaced:
- 4 wheels and tires swapped from another SLK (no fix)
- 2 front struts KYB (struts bad according to tire wear)
- 2 front wheel bearings and cleaned ABS rings (fixed BAS/ESP light only a little while)
- transmission mounts
- drive-shaft flex disks
- drive-shaft center bearing w/ bracket
- drive-shaft u-joint bearings (yes it's replaceable)
- 2 rear wheel bearings
- 2 rear wheel knuckle bushings
- 2 rear brake rotors
- 2 rear parking brake shoes

At first I replaced the 2 front struts according to the tire wear pattern. No fix. Then I replaced both front bearings. Fixed the BAS/ESP light for a while. Soon the problem gets worse. The whole car was shaking at high speed. From the bottom to the steering wheel. Inspected the drive shaft and found a few minor cracks on the flex discs so I went the whole 9 yard and replaced the center bearing and the rubber bracket, along with transmission mounts, and the u-joint bearings. Result was a big improvement, yet some vibration is still there. It still throws the light but on and off. On good days you hear it but you don't feel the shaking. It seems to go away on hard throttle or braking.

The car is 6 speed manual shift. 110k miles. Clutch engages pretty well. Shaking still happens when clutch in or gears in neutral.

Today I found myself playing with the front wheel bearing preloads. I think I need help. The problem is driving me crazy and making every ride unpleasant for these years. I only put on 6000 miles last 5 years.

Here are the codes I have:
C1025-2 CAN bus: CAN message ABS is faulty
C1100-4 L6/1 (left front speed sensor):Loose contact
C1101-4 L6/2 (right front speed sensor): Loose contact
C1140-128 N49(Steering angle sensor): Steering angle sensor is not initialized
C1142-1 B24/2 (ESP lateral acceleration sensor): Electrical fault
C1142-4 B24/2 (ESP lateral accelaeration sensor) : zero point variation
C1142-16 B24/2 (ESP lateral acceleration sensor): Singal cable has open circuit or short circuit
C1202 A7/7s1 (BAS release switch) : Plausibility
Vario Roof code: B1268 Speed sensor: status signal is invalid
N1140 CAN Bus-fault

Any help is appreciated. Thanks in advance.
 

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Crikey, I really don't know where to begin, this a really tough one and you have listed far more than I would have suggested.

I will have a think and suggest anything I come up with. As it is a manual, does it have a dual mass flywheel in the clutch?
 

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Discussion Starter · #3 ·
I think it is.
I have an oil leak coming down between the transmission and engine area. Can't find where it come from but I'm pretty sure it's engine oil. It's not the ATF pink color. Yes, it takes ATF.
So it could have a leak at the engine main seal. It wouldn't cause vibration.
If the gearbox is leaking, then I could have a damaged clutch bearing.. It does sound like a bearing.
I also had a differential leak at the pinion gear bearing seal. But it's gone after I replaced the flex disks and u-joint. I am thinking excess vibration from the shaft could be the cause of leak.
The shaft needs balancing, which I haven't done. Most shops quoted $300-400 just for a balance. Just found a place can do $125. It will take a week.
However balance issue affects most at high speed. Mine is the opposite. Less noise when going fast.

Tomorrow I will try to top off differential fluid. It could be running low.
 

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I've had two similar problems over the years, the first was on a Volvo and it turned out to be a loose prop-shaft, the other was on a crappy fiat with a bent drive-shaft, might be worth checking those out?
 

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When you say "Shaking still happens when clutch in or gears in neutral.", is that standing still or when moving?
I had a problem with a different car of mine that had a speed dependent vibration. Turned out that the tires had internal construction problems that were diagnosed when I went to a tire shop that had a road force balancing machine.
A road force balancer simulates the pressure the car applies to the tire contact patch by having a drum come up and contact the tire while it is on the computerized balancer. The computer reads the forces applied to the drum.
May be your problem or may not but it is something to think about.
 

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Discussion Starter · #6 ·
I mean when it's moving. Engine revs smooth when car is still. That rules out engine mounts.
I can sure use some balancing machine. Need to research on that.
But first thing I need to get the driveshaft balanced since I replaced the u-joint.
Tires need replacing too since they are running low anyways.
Maybe 2 new struts for the rear.
Just can't stop throwing on new parts.
Anyone know how strong the differential is? Looks pretty small and wonder if it handles the extra torque of 320, specially the gap between 1st and 2nd gear puts a lot of stress on that diff.
Wonder if I should do a rebuild.

How's other 320 running out there?
 

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I believe read something recently saying when changing break pads n shoes to always renew the rotor arms. Not sure if that helps you, but thought I'd suggest it.

Good Luck. Sounds like you need it!

Regards

Steve
 

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Discussion Starter · #10 ·
I'm not exactly sure where is the rotor arm? Is it one of the control arms?

UPDATE: Just got rid of the noisy Good Years and put on new Dunlop DZ102 rubbers. The vibration is much less but still happens and triggers the BAS/ESP light after driving for a while.
 

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I mean when it's moving. Engine revs smooth when car is still. That rules out engine mounts.
Actually it doesn't rule out mounts and that maybe where your problem lies. There is little load on the engine when you are in neutral and you can rev the crap out of it and it will move very little even if the mounts are shot. Put it in gear and it's a different story. Good news is it's pretty easy to check motor mounts.
 

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Mercedes Benz of San Francisco does road force balancing.
I had replaced a lot of parts on the Camaro that had the vibration problem. I finally found a clue to what was wrong when I put the car on jack stands. I then slowly brought the speed up to the vibration point and nothing happens. No vibration.
Scratched my head for a few minutes then hit on the road force issue.
It might not be your problem but is a cheap way to eliminate it from your list of possibilities.
 
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