I am a 84 380se and I got the rotors turned down but still get a noise when braking...thump thump Anyway it only happens while braking. Could it be a caliper or something else. IF its a caliper how do I know which one it is before I warp the rotor? Thanks Karl

MB rotors should never be turned down. From your description I'd say the rotors are warped already. Use a dial indicator to check the runout. Also, use a micrometer to see if the rotors are below the minimum thickness. If so, they should be replaced immediately.

__________________
Fred Hoelzle

originally posted by Ferdman

"MB rotors should never be turned down. From your description I'd say the rotors are warped already. Use a dial indicator to check the runout. Also, use a micrometer to see if the rotors are below the minimum thickness. If so, they should be replaced immediately."

Exactly

1) 84 model year with aftermarket discs. may be able to take a lathe resurface? But new disc are the way to go, lots of MB shops have throw out their lathes.

2) first you have to make sure it's not a malfunctioning ABS, your car have ABS, which shouldn't be hard detect if that is the cause.

3) Your talking about noise and not feel so lateral runout of a disc when braking should cause some vibration, Is your thump thump just noise or do you feel it and where do you feel it? hands, seat

That car dosen't have rear drum brakes does it?

no discs all around. I never heard that you can't turn down the rotors. Would that cause the thump thump in the braking then?

Most shops don't have the skills or equipment to turn down the rotors within MB specs. The thumping is most likely caused by uneven rotor thickness. The uneven rotor thickness causes the pistons to move in and out as you step on the brakes. You'll feel this in the pedal.

Yes, buy new rotors.