Brakes! - PeachParts Mercedes-Benz Forum

conor · #1 06-05-2008, 01:27 AM

These things will be the end of me! On my 1978 300D I heard the pads hitting the rotor at a spot at every rotation, so I replaced the calipers and hose and bled it best I could. It seemed like the right thing due to the fact that the pistons were stuck.

Well, the noise is still there. Is it safe to assume the rotor is warped? the rotor looks fine, yet it doesn't seem to be bad wheel bearings due to the fact that there isn't any shimmy in the wheel. thoughts?

BoomInTheTrunk · #2 06-05-2008, 01:52 AM

well if you ran the pad down enough to damage the caliper i doubt the rotor is still good. if the rotor is warped you aren't going to tell by just looking at it. take the wheel and spin it, if it grabs at certain spots than the rotor is defiantly warped. If it doesn't then the possibility is still there that they are warped.

conor · #3 06-05-2008, 02:25 AM

Quote:

Originally Posted by BoomInTheTrunk

well if you ran the pad down enough to damage the caliper i doubt the rotor is still good. if the rotor is warped you aren't going to tell by just looking at it. take the wheel and spin it, if it grabs at certain spots than the rotor is defiantly warped. If it doesn't then the possibility is still there that they are warped.

I don't know what you mean by ran the pad down enough to damage the caliper...the pads were/are fine. I replaced the calipers because the piston was stuck, probably not needed I dont know, but the pads didn't wear. I just check to see if I could rotate the wheel and found a very small leak from the valve, probably not an issue. In any case, I could not rotate the wheel very well because the pads were shut around them. If the rotor were warped, wouldn't I hear the pads hitting all the time? In my case, the pads only hit after I've been using the brake.

BoomInTheTrunk · #4 06-05-2008, 02:34 AM

oh my bad i read it wrong. the pads always touch the rotors just a little but if they catch when you spin the wheel freely then the rotor is warped. Did you put anti squeal paste on the back of the pads, and are the pads or rotors glazed over. If they are glazed over the pad or rotor will look like glass in some ways. if they are they need replacing.

conor · #5 06-05-2008, 02:43 AM

No anti-squeal. the wheel turns without catching. The rotors are very smooth. I don't know what a rotor is supposed to look like, but it is really smooth with fine groves in it.

I don't understand why only after I brake hard a few times does the pad start hitting the pad.

BoomInTheTrunk · #6 06-05-2008, 03:01 AM

Quote:

Originally Posted by conor

No anti-squeal. the wheel turns without catching. The rotors are very smooth. I don't know what a rotor is supposed to look like, but it is really smooth with fine groves in it.

I don't understand why only after I brake hard a few times does the pad start hitting the pad.

the pad hitting the pad?

conor · #7 06-05-2008, 03:10 AM

yeah, there's no rotor. I took it out a couple of weeks ago. Sorry, I forgot to mention that. I figured the pads would be enough. No, sorry, let me try that again: "I don't understand why only after I brake hard a few times does the pad start hitting the rotor." (a continuous scrape, scrape, scrape after I hit the brakes hard.) At least that's what it sounds like...

BoomInTheTrunk · #8 06-05-2008, 03:15 AM

the calipers are still sticking then you would get that and if they are making a noise in a rhythmic pattern than the rotors are warped. Rebuilt calipers can be bad to and stick to, took me 2 months to get working calipers and i ended up buying brand new calipers not rebuilds just to get it right.

tangofox007 · #9 06-05-2008, 09:10 AM

Quote:

Originally Posted by conor

"I don't understand why only after I brake hard a few times does the pad start hitting the rotor." (a continuous scrape, scrape, scrape after I hit the brakes hard.) At least that's what it sounds like...

Jack the offending wheel off the ground. Then hit or kick the tire adjacent to the caliper and again 180 degrees opposite the caliper to loosen the brake pads from the rotor. Then rotate the wheel by hand. If the "scrape" is still present, it might be time to look at your wheel bearings.

ajcbgray · #10 06-05-2008, 10:33 AM

I had what I thought was a sticking caliper and it turned out that my master cylinder was on the way out and not fully releasing pressure to the rear brakes causing the drag.
If your brakes drag and over heat they will either warp the rotor, or pad material can adhere to the rotor causing a high spot that hits when the wheel rotates (that happened to me). Do you also feel a pulsing when you brake?

conor · #11 06-05-2008, 12:22 PM

Quote:

Originally Posted by ajcbgray

I had what I thought was a sticking caliper and it turned out that my master cylinder was on the way out and not fully releasing pressure to the rear brakes causing the drag.
If your brakes drag and over heat they will either warp the rotor, or pad material can adhere to the rotor causing a high spot that hits when the wheel rotates (that happened to me). Do you also feel a pulsing when you brake?

no,
there isn't really a pulse feeling. Basically, theres no problem much of the time - no noise. But after I've been braking hard like going downhill, exiting the freeway, stop and go, then the rhythmic scraping noise begins and usually goes away eventually after both not using my brake and keeping a good speed, such as freeway driving. If I had the noise from stop and go before I get on the freeway then it usually goes away after I've been on the freeway for awhile.

conor · #12 06-05-2008, 01:34 PM

new revelation: after a spin, it seems like the front brakes are good, and instead the right rear is scraping. -Warped rotors I'm pretty sure.

ajcbgray · #13 06-05-2008, 01:50 PM

If you don't feel any pulsing when you brake I don't think you have a warped rotor. It could be the e-brake dragging or something rubbing. I'd pull the rotors off, clean everything up and try to isolate the sound with the wheel off.

conor · #14 06-05-2008, 02:01 PM

I'm pretty sure the noise is coming from the pad hitting the rotor. My theory is that while driving my braking is the causing the pistons to stick out more pushing the pads closer to the rotor which makes the pads more susceptible to any warp in the rotor. Since after driving awhile and braking I hear scraping at every rotation, I assume the rotors are warped. I'm actually trying to get the car ready to sell by this weekend!! So, I don't think I'm going to fix it if it's a rotor...

BoomInTheTrunk · #15 06-05-2008, 02:10 PM

well if it is the rotor just fix it, they are only like $34 or something like that. just have to use a 10mm allen wrench or socket to get the hub off.