Yeesh! if you start hearing noises from the brakes, INSPECT them!!! - PeachParts Mercedes-Benz Forum

vstech · #1 09-21-2007, 01:53 PM

the rear brakes on my SD started making a squeel last week, so I put up a mental note to check them out, well wednesday I started hearing more noise from back there when I would hit the brakes gently... so I pull off the wheels, and look everything over with a new set of pads to go in... well I got my money's worth out of THOSE pads... odd thing is the outer pads on both sides of the car were MUCH thinner than the inner side... odd. also the rotors had a good ridge... I guess I will need to replace those pretty soon...
anyway, I decided to check the brake fluid... don't think I EVER flushed it on the SD... 7 years... oops. anyway, that stuff was rank and chunky... I am SO glad it was not siezed. I flushed the accessible resivoir, but could not get to the front tank... how do you clean out the front tank on the MC???

bodyart27 · #2 09-21-2007, 02:21 PM

As you have found out the resevoir is split front/rear. If you can not siphon out both (with a turkey baster for example), you'll have to just bleed the calilpers - which you should do anyway during a brake job. Just putting new fluid in the MC is not enough anyway. When brakes get hot, it's the water that has creeped into the brake fluid sitting in your calipers that can boil. Go do a bunch of 60-10 mph stops in succession and I bet your pedal starts to "fade" and go to the floor.

That's the water boiling to vapor in your calipers that is compressing (gas compresses, fluid does not) giving your pedal the extra travel (that or your brake lines are bulging - I've replaced all mine due to age as a precaution).

I recently did a brake job for my mother-in-law on her 94 Jeep Cherokee and I think at 80K miles her car had the original brake fluid and pads. The fluid looked like dark ice tea. Super nasty old stuff.

When you do the pads and rotors just give the whole system a good flush. Start bleeding the system from the caliper that is farthest from the MC (passenger rear > driver rear > passenger front > driver front).

vstech · #3 09-21-2007, 02:25 PM

for sure, a full line flush is best, but I always empty the reservoir, and wipe down all the walls where various bits of gunk accumulate... impossible on this type of resivoir... and a flush is going to be useless... how to get out the bad... hmmm.

pawoSD · #4 09-21-2007, 03:07 PM

Thanks for reminding me, I was going to flush my brakes recently but forgot. I am at almost 2.5 years....so not toooo bad, but it needs to be done.

bgkast · #5 09-21-2007, 03:09 PM

I'm flushing mine this weekend. The stuff in there now looks almost black!

bodyart27 · #6 09-21-2007, 03:41 PM

Quote:

Originally Posted by vstech

and a flush is going to be useless....

Why is that?

linguica · #7 09-21-2007, 06:43 PM

Quote:

Originally Posted by vstech

for sure, a full line flush is best, but I always empty the reservoir, and wipe down all the walls where various bits of gunk accumulate... impossible on this type of resivoir... and a flush is going to be useless... how to get out the bad... hmmm.

with rags close by. That way you wont have to bleed the chunks through the system.

pawoSD · #8 09-21-2007, 06:56 PM

Easier said than done....when we tried to do that (during brake system disassembly), we broke one of the nipples off of the resevoir (plastic was old), and $90 later it was all set with a shiny new one.

linguica · #9 09-21-2007, 07:18 PM

Good point! I guess I was lucky. Mine came right out and slid into the new bushings on the new MC and I was on my way.

Mustang_man298 · #10 09-21-2007, 11:17 PM

Quote:

Originally Posted by vstech

odd thing is the outer pads on both sides of the car were MUCH thinner than the inner side... odd. also the rotors had a good ridge...

Your caliper slides are either seized or getting close, making the pad opposite the piston drag, make sure they get cleaned well and lubed lightly with caliper lube. Even just being dry and dirty can cause them to not release correctly. Sticking slides cause one pad to wear out faster, sticking pistons will cause even but rapid wear on both sides, and usually overheating.

When I got into unseizing the brakes on the 80 (sat for 4 yrs in a backyard, I touched the pedal once and the wheels locked solid, made it interesting getting it off the trailer) I purged the MC by using an old large syringe I keep in my toolbox, slurped out the first side and slipped a good sized needle thru the top of the divider wall to get the rest, "powerwashed" the bottom and sides with new fluid in the syringe to break loose the sediment and then slurped it again. Worked pretty well.

Hatterasguy · #11 09-21-2007, 11:26 PM

I just threw a new set of pads on the front, after 30k miles the old ones were shot. However the new OE pads are total trash.

They squeal to no end, and now I hate ATE rotors as well, total trash!

They warped, after 30k miles!

The original calipers are not to hot either.

My front brakes are now total squeling, pulsating junk, I'm going to throw them away this winter and replace the whole system. The ABS is acting up as well.

However my rear X drilled Zimmermans are holding up very well!

So this winter, X drilled Zimmerman rotors up front, rebuilt calipers, Textar pads, new caliper bolts, stainless brake lines all around, and new ABS sensors.

Lots of new parts up front this winter!

waybomb · #12 09-22-2007, 10:19 AM

Quote:

Originally Posted by Mustang_man298

Your caliper slides are either seized or getting close, making the pad opposite the piston drag, make sure they get cleaned well and lubed lightly with caliper lube. Even just being dry and dirty can cause them to not release correctly. Sticking slides cause one pad to wear out faster, sticking pistons will cause even but rapid wear on both sides, and usually overheating.

When I got into unseizing the brakes on the 80 (sat for 4 yrs in a backyard, I touched the pedal once and the wheels locked solid, made it interesting getting it off the trailer) I purged the MC by using an old large syringe I keep in my toolbox, slurped out the first side and slipped a good sized needle thru the top of the divider wall to get the rest, "powerwashed" the bottom and sides with new fluid in the syringe to break loose the sediment and then slurped it again. Worked pretty well.

To this point - sometimes you may even have to use a file to get all the old rust off. Then sand smooth, and coat with something like SylGlide. On all parts that touch. It's a silicone based caliper slide compound.

funola · #13 09-22-2007, 10:48 AM

Take the MC off. Fill with brake clean, shake, dump, reapeat, fill with brake fluid, shake, dump, repeat.

Quote:

Originally Posted by vstech

for sure, a full line flush is best, but I always empty the reservoir, and wipe down all the walls where various bits of gunk accumulate... impossible on this type of resivoir... and a flush is going to be useless... how to get out the bad... hmmm.

vstech · #14 09-22-2007, 05:50 PM

Quote:

Originally Posted by Mustang_man298

Your caliper slides are either seized or getting close, making the pad opposite the piston drag, make sure they get cleaned well and lubed lightly with caliper lube. Even just being dry and dirty can cause them to not release correctly. Sticking slides cause one pad to wear out faster, sticking pistons will cause even but rapid wear on both sides, and usually overheating.

ok, for everybody who does not already know, the 123/126 (and possibly others) brake calipers have no slides... it is a fixed dual opposing piston caliper. there is nothing to lubricate. proper flushing of the lines/caliper/master cylinder is the best you can do for preventive maintenance.
now the piston boot, can it be replaced? mine was pretty worn out.

waybomb · #15 09-22-2007, 06:30 PM

Quote:

Originally Posted by vstech

ok, for everybody who does not already know, the 123/126 (and possibly others) brake calipers have no slides... it is a fixed dual opposing piston caliper. there is nothing to lubricate. proper flushing of the lines/caliper/master cylinder is the best you can do for preventive maintenance.
now the piston boot, can it be replaced? mine was pretty worn out.

Yes, there is something to clean rust from and lubricate - the brake pad backing gets stuck in the caliper as it slides back and forth. I know, Mine were stuck on my 126. Had to beat the pads out. All of them were stuck from rust and other gunk. Had to file the area and sand it, then lubricated them all.