My 420 SEL is making a weird noise that sounds like a ghost coming from possibly the bottom and rear of the car only when you are driving, hit the brakes to a stop, and then hit the accelerator. The kicker is that it does not happen all the time, so my tech could not hear it, but it is happening a little more frequently now.

The only thing that I had done a week ago is I had my tires rotated and the guy said that since the last time your tires were rotated, someone did not tighten the bolts all the way on one wheel, your bolts became bent, so we will have to replace the 5 or 6 bolts. They did it for free so I said no problem.

4 Days later I am getting this weird noise sporadically now and then after I let go of the brake(not exactly sure where it is coming from). Is there something that could have happened the to the brakes, wheel, rotor, disks, etc., from replacing warped bolts (causing from being too loose).

My Tech checked the brake fluid and the tranny fluid is fine. Alhough it is not applicable, I got new plugs and "suppressors".

It is possible that it has nothing to do with the wheels. Maybe someone had heard a noise like that and had a different problem.

Any feedback would be greatly appreciated.

How about the rear? Differential? Tranny ?

You have to tell us what a "Ghost" sounds like. Does it say BOO! or is it a more friendly sound like Casper the friendly ghost might make?

Smiles.

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Earl



1993 190E 2.3
2000 Toyota 4x4 Tundra

So a week ago, it was fine. Did the rotation and the ghost awakens. At what speed?

Do we understand correctly that when you step on the brakes, it kills the ghost?

__________________
... Kerry

126 tailed by a 203, 129 leading the pack.

Without sounding rediculous, the "ghost" sounds more like something you would hear on Scoobie Doo, like uhhhhhhhhhhhhhhhhhhhhhhhhhhhhhh, coming in, fading out, sporadically. It does not happen everytime. It can also be described as a "humming" like mmmmmmmmmmmmm or a "howling" oooooooooooo (deep and loud coming from the pit of your stomach).

When it does happen, it seems to happen after the car has been running a while and after you let go of the brake and accelerate, i.e., after a red light, usaually for a short distance, the most right now until the car reaches 25 mph.

If and when it happens and you apply the brake, YES, it does kill the noise.

I know this ghost noise sounds rediculous, so please don't kill me with any jokes. I would not believe it until I heard it myself.

I think it has to do with my tire rotation and the guy saying he has to replace the bolts. Something is going on inside one of the wheels, i.e, the cover, rim, disc brakes, etc. I don't know how it works inside there so I cannot fully think of how that noise can develop from the wheel rotating after a stop and why the brake dampens it.

Perhaps not having the wheels tightened properly cuase pre-mature wear to the wheel bearing. Now that wheel is within spec, the sound is prominent.

Well, a ghost in the machine. Sounds like (no pun intended) a vibrating brake pad or..a rotor that is warped. Either will produce funny wavering low frequency vibration. If all else is well, I would have the brakes checked throughly.

__________________
Jeff Lawrence
1989 300e
2000 Dodge Grand Caravan SE
No matter what you fix, there will always be something else to fix..
"Warranty" is just another way of postponing the inevitable.

Do this. Put your car on jack stands and rotate the wheels by hand to see where the problem is. It may be minor. There is bracket for where the brake lines are behind the wheel. If the brake hose is positioned a little off. You may get a weird noise.

Thanks for your replies.

I took it back to the place where I got the tire rotation. After a test drive of 5 miles, the noise happened as soon as we came back to the shop. It appeared that it was coming from the back of the car somewhere. He said that he never heard a howling noise just like that. The closest was is he heard something close to that, there was a problem with a differential, but that noise was constant at all speeds no matter what you did. My sound goes away as soon as hit the brake. A young Tech spent over an hour taking both rear wheel brake assemblies a part.

The only thing out of the ordinary was that the passenger rear rotor would not come off by hand. He had to heat it up with a blow torch. It finally came off nicely after that. After taking both rotors off, there was nothing that appeared to cause a noise with the naked eye.

The only thing that he noticed is that one of the two rubber transmission mounts was cracked near the engine up front and with a crow bar he was able to lift the differential. Probably not the cause of the noise, but something that needs to be fixed.

It did not make the noise on the way home, so I am hoping that just taking the rotors off and putting them back on will re-situate them correctly. Don't know. Time will tell.

After taking it to the mechanic and getting the brakes apart and looked at, as I mentioned in an earlier post, there were no problems that can be seen with the naked eye. The noise did not occur again until two days later and has been doing it again everyday since. Any other things that could possibly be causing the noise? Thanks!!

Next time the noise occurs step on your parking brake to see if doing so has any effect on the noise. It might be your parking brake shoes or lose cable.

[Edited by ejsharp on 05-09-2001 at 03:04 PM]

__________________
Earl



1993 190E 2.3
2000 Toyota 4x4 Tundra

Does this car have a self-leveling suspension?

Thanks for the info on the parking brakes. Although the parking brakes have been checked twice & nothing seems to be wrong with it, I'll definitely try your suggestion & see what happens.

As far as the self-leveling system, the answer is YES. Don't all 126's have that?

Thanks again.

As for W126's, only the 560SEL has the self-leveling suspension.

I don't know what the leveling system has to do with the noise, but in any case, that surprises me that the only the 560 has it. To me, it just does not make sense. I thought I read that I had it in my manual, not sure.

I've had a couple Volvo's that made that noise and it was caused by the center support bearing on the drive shaft. The sound is kind of a cycling whine that changes octave with the speed of the car.

I'm not very familiar with Mercedes yet and I'm not even sure if they have a center bearing on the drive shaft but if they do I would strongly suspect that's the problem. A test I've used on Volvo's to tell if the bearing is the cause is to use a grease gun with a grease injection needle and shoot some grease into the bearing through the rubber seal on its side. The noise is usually caused by a dry bearing and the grease will temporarily stop the noise. This should not be done as a permanent fix though.