Rotors warped again.. - PeachParts Mercedes-Benz Forum

bhatt · #1 10-28-2002, 04:47 PM

Hello all..

Bought a 300SDL about 1.5 years ago and have since driven 20,000mi. When I bought the car, the rotors were smooth with no vibration or pedal pulsation while braking. Within 2000 miles or so, the brake pedal started pulsing while braking and I had a slight vibration around 60-80mph. Assumed PO had torqued the lug nuts improperly and this caused the rotors to warp.

Put on a new set of rotors after driving the car 3,000-5,000mi or so. Those did it again after a few thousand miles! I've been driving with warped rotors for the last 15k mi or so and it's driving me nuts!!

Rotors were replaced with OE type Balo rotors. Noticed at the time pads looked brand new even though I had already driven 5000 miles + whatever the PO drove since he had them changed! I've since driven another 15k and the pads still look like they haven't worn down much compared to new pads (looks like 80% pad life left!) Brakes make groaning sound when coming to stop sometimes.. Did NOT replace these pads when doing rotors.. they've been on the car 20,000mi +++ (WEIRD!)

Should these pads have lasted this long with no noticeable wear? My guess is that he had cheap "lifetime warranty" pads on the car and they're screwing up the rotors. .. does this make sense?

I'm going to check the back brakes to make sure they work, but am I wasting time throwing a new set of Balo rotors and Texar pads at the front axle? Or is there anything else I can check before I warp another set???

Thanks!
Neal

'86 300SDL 256,000km (154k mi)

jsmith · #2 10-28-2002, 05:22 PM

check for sticking pistons in one of your calipers. i had a similar problem in another vehicle and discovered it when i had installed new rotors and pads. one wheel got abnormally hot to the touch. turned out that one caliper had a sticking piston which probably caused the original warping problem.

bhatt · #3 10-28-2002, 10:06 PM

Thanks jsmith..

How do I check for a sticking piston? I know how to pull the pads from the caliper and push the piston back in to install a new pad.. if the piston goes back in am I OK?

If I recall correctly, all 4 front pads were wearing equally.. If a piston were sticking, would one of the pads be worn down more than the others or would it look the same?

Neal

#4 10-29-2002, 02:13 PM

I worked for Buick for 5 years and had several classes on ABS. The warping of rotors generally occurs when an excessively hot rotor comes in contact with water. When washing your vehicle avoid spraying water directly on brakes and avoid driving through water in roadway after moderate to hard braking. The best thing you can do is just practice good braking habits.
Oh, and the groaning is a sure sign of hard braking in heavy water conditions, causing pads to glaze. You can try sanding the glaze off the pads with a medium emery cloth.

bhatt · #5 10-29-2002, 03:54 PM

No dust shields on the car, and I generally run it through the car wash twice a month. Prior to the wash, I spray rim cleaner on and scrub a bit with a brush. Because of this "prewashing" of the rims, the car sits still for 2-3 minutes, with another minute or two lined up to get into the wash.

Assuming I'm not hitting the brakes hard for a few minutes before the wash, I'm only applying the brakes once or twice in the last five minutes before the wash. . could this still be causing them to warp?? I've never warped rotors before and have driven cars with much thinner and cheaper rotors (I've driven the worst of them all.. '85 and '87 T-Bird, notorious for warped rotors but never experienced it. '85 Sunbird, '90 Geo Storm with paper-thin rotors, etc.)

Neal

psfred · #6 10-29-2002, 08:34 PM

Gee, I must talk too much!

Several causes of warped rotors, but the leading one is probably very hard braking and then sitting at a complete stop, so the pads insulate the part of the rotor they cover.

Get those pads out of there, they are at least glazed. Groaning or squealing means aftermarket, rock hard pads, and they are probably the cause of your warped rotors -- too hard, glaze, then cause you to use too much braking effort, overheating them.

You need to driver VERY gently for several hundred miles on new pads. Try to avoid "panic" stops (hard enough here, let along in major traffic!), and make several firm stops from 35 mph with as much cooling time as you can between to wear the fur off the new pads after you put them in.

Definitely check the rear brakes. Rear rotors can warp, and if the parking brakes were dragging (from not releasing the parking brake) and then adjusted too tight, they can rumble, too. Won't get worse when braking, though.

A sticking piston can make the car groan at low pedal pressure stopped. Can also make the car jerk when coming to a complete stop with light pedal pressure.

On my Volvo, I think i have either a sticking piston/s up front, or air in one circuit that makes the pads vibrate. Not a rotor problem, as heavy pedal makes the noise and vibration go away.

If the rotors were run underthickness and the pads jammed on the antirattle spring, caliper rebuilds are in order. This is easy, the only really hard part is getting the piston back in at the correct rotation point -- impossible to move in the bore without the special tool.

Peter

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