I replaced my rear brake rotors, pads and sensors only about 7,000 miles ago with MB rotors and pads from a dealership. When I took them to a shop just recently they indicated that the rear rotors are scored. When I'm on a freeway and apply the brakes I hear a slight cavitation. IS there something going on with the calipers?

Cavitation ???

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A Dalton

yes, it sounds like the rotors are scored that's what I mean by cavitation.

Oh...I see,
You kinds threw me there....
Cavitaion is when the hydrylics are cavitating b/c of a mixture of air/vapors with the fluid when under pressure .


If your rotors are scored I would be looking at possible brake hose constriction or caliper binding..not fluid cavitation.
[ or cheapo brake pads]

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A Dalton

Hearing a cavitation wouldn't cut it for me - I want to see it with my own eyes. Then I'd probably want to rename it. Sadly not all brake shops all impecably honest on these things. Rear brakes get so little wear it's unimaginable that you have damage on your rear rotors in 7k miles, especially with soft dealer pads. In any case you need a second inspection/opinion, starting with confirmation that the noise is coming from the rear.

Thanks for the info. Must be something going on with the calipers.

I replaced the rear rotors because the shop said they were being scored (as explained by the dealership). When driving at high speed I cold hear the breaks making a noise (a cavitation like sound, for lack of better word to describe it). I replaced the pads and rotors with MB dealership parts and they sounded fined, But now I think I'm hearing it again after only about 7k miles.

So there must be something going on with the calipers, but was just wondering if there was something else I should have done besides changing the pads (i.e. lubricating any moriving parts, etc.).

Also, I think I'm going to look into getting the older rotors turned as they seem to be acceptable (thickness wise).

Thanks for the info.

mayr71, you may need new rear brake hoses. Older, collapsed brake hoses prevent the caliper piston(s) from retracting properly resulting in premature wear of the brake pads ... or there is rust between the piston and caliper bore preventing the calipers from functioning properly.

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Fred Hoelzle

Well I had a Mercedes mech check out the calipers and their functionality.

He said that the calipers were operating fine, but my 7k old rotors are warped. He noticed that the wheel lug nuts were very tight and that this could cause the rotors to get warped.

So I need new rotors again. Have you hear about lug nut torgque affecting the rotors this way?

Absolutely....there is a specific procedure and torque specifications to tighnening the lug nuts......

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A Dalton

mayr71, buy a torque wrench and torque the lug bolts on your 1995 E320 to 80ft/lbs. The actual specification may be 81ft/lbs, but I dislike odd numbers.

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Fred Hoelzle

As I posted, it is not just the torque specs that effect the proper seating of the rotors..it is an incremental tightening sequence procedure that must be used. It is referred to as the "Star Pattern" and this should be imployed. Simular to head bolts having a numbered sequenced procedure.

The problems arise when Gearheads slap your wheels back on with the speed of a Video Game , using an Air Impact Gun set on MAX....


Most Owners Manuals have that info listed.

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A Dalton

i just had my wheels balanced and had to specify 80 ft-lbs at Merchant
tire. i felt like if I wasn't there they would have thrown them on at 100lb-ft.

thanks for all the input.

Cool...a tip for ya at those discount tire joints.....

If the guy ask if you "Want Fries wit dat ?? " , ask if he would not mind if you had his Boss tighten the lug nuts ....

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A Dalton