jrs

Hi,

My 97 E420 (98k miles) has a pretty bad shake/vibration when brakes are applied with medium pressure on the pedal. When I increase the pedal pressure, it goes away.

Rotors and pads were replaced on all 4 wheels, which had no effect on the problem. Tires are in good condition and inflated properly.

Any suggestions would be greatly appreciated, thanks in advance.

John

MARK CUMMINS

Sounds like defective Brake rotors..Take it back to the shop that did the Brake job...
Did They Replace the rotors or turn them?
Have The Shop Use a Dial Indicator to Measure runout on the rotors....
If they replaced the rotors you should NOT have a Brake Pedal Vibration...When Stopping

jrs

Hey Mark, thanks for the reply.

I hear you on the rotors, but here's what makes me wonder:

I initially had a brake vibration and did a complete brake job (I had the rotors machined). The vibration persisted.

In my next attempt, I had a second set of front rotors machined by the same shop, and I installed those. The vibration exists exactly the same, with 2 different sets of front rotors, and each set had just been machined. That's what makes me suspect possibly something other than the rotors.

I know it's possible, however, that I could have 2 sets of front rotors that came back from the machine shop with unacceptable runout. How likely, is what I'm asking myself.

So at this point, would you recommend trying a third front rotor set (new this time)? Or is it likely some other problem these cars are prone to having (flex joint, control arm bushings, etc)?

Thanks again, I appreciate it, John

MARK CUMMINS

I Would think that the Rotors are the Problem..
You can Get Brand X with Quality Issues What Brand of Rotors did You Purchase?

The W210s do have Problems With the Lower Front Control arm Bushings..Take a look at them....
They Make a Knocking Sound/clunk When Defective

jrs

One of the 2 sets of rotors I'm using is Brand X (don't recall the actual name), the other set is the original rotors. The vibration is identical with both rotor sets.

But, I do also get a clunk from the front end when going over a bump.

So at this point, maybe a dealer diagnosis makes sense, rather than trying a third set of rotors. If it is the control arm bushings, I'm probably not equipped to do that job myself.

Randy B

jrs,
When you say machined, do you mean cut or turned????? If so, I would say pick up a new pair of rotors readily available for your car for abour 59.99 each side, and see what happens. Sounds to me like the turning may have leveled the surfaces out, but perhaps one side is thinner than the other. Measure them with a caliper if you can and see what thickness you have total as well. Remember these rotors are designed to wear with the pads and perhaps the machining has cut them down too far.

jrs

Randy,
The rotors were turned, and the shop claims to have checked to ensure they still had the minimum allowable thickness. But I didn't measure them myself after I got them back - I appreciate the suggestion.
John

Randy B

BTW John,
When I had my 99 E430, I would cut the discs once, and then replace on the second brake job. I do not know where you are with yours, but the replacements are quite reasonable. The whole job used to take me about 1 and half hours to do the front. Real straight forward. I 'm about to do the first brake job on my new E500. I hope it is as straight forward as the E430 was.

jrs

Well good luck with the E500 Randy, I'm sure you'll have more success than I seem to be having!

I turn my rotors once as well; that's always worked for me in the past.

gstigler

Your problem is most likely the rotors. MB recommends replacement and not turning them. Get new ones (they are about $50 a piece) and let us know if the problem persists.

mb-mopar nut

luke sent me this link about warped rotors

http://www.stoptech.com/whitepapers/...otors_myth.htm

also, the problem may be due to loose calipers or road vibrations, I feel it on certain roads at certain speeds.