brake problems- I really, really, dislike brake work! - PeachParts Mercedes-Benz Forum

RG5384 · #1 03-10-2002, 12:53 AM

Well i have a new interesting problem with my 83 300SD. When braking at slow speeds, there is a very noticible moaning coming from the front. Second, when i did a fast stop and let off, the car jerked to the right immediatly after i left off-sticking caliper? I then did several "panic" stops and could not duplicate the pull to the right. I know my car needs rear brake pads quite bad, could this be causing these problems? Also, how many times should you be able to pump the pedal before you run out of booster pressure(power brakes). Thanks
Ryan

Mercedes Man · #2 03-10-2002, 12:07 PM

Which brand of brake pads do you have? I replaced the Mercedes brand with Raybestos, and they squeak and make a little grinding noise at low speeds. The Mercedes brakes had anti-rattle shim that I could not make fit on the Raybestos. The Raybestos have a shorter braking distances.

As far as pulling. you can tell which caliper is pulling by driving the car for some distance and feeling the temperature of the rims. The hottest rim is the caliper that has the problem. You can also drive the car down a quiet street with no cars on it. Then you let of the wheel and slam on the brakes. The car may suddenly go right or left! From here, you have to decide which caliper is sticking. In my experience, bad calipers usually drag, and the car will go the direction of the dragging caliper. Sometimes the caliper freezes in the bore and only one brake works. The car will go the direction of the working brake.

You can also jack up the car. Have someone spin the wheel, and you hit the brakes. If the wheel doesn't turn freely after hitting the brakes, the problem is in that wheel.

Capt Kirk · #3 03-10-2002, 12:35 PM

I just wrote up a how to on brake system work that is going on the FAQ page. It's really not that hard to do once you know what the problem is.

It's most likely a caliper that is sticking or not engaging. You should also replace the pads that are really worn down cause if they get to bad you can mess up the rotors and the calipers.

vwbuge · #4 03-10-2002, 04:52 PM

First I would try to bleed all the brakes. Then if that doesn't work Take the calipers off and disassemble, clean and put back together. If that fails buy a new caliper. 'Nuff said. Mercedes has THE easiest brakes to work on.

RG5384 · #5 03-12-2002, 04:08 PM

thanks for the replies. I completely agree that brake's arent anything to overlook, and that i need to look at the problem. So far, no ill symptoms have returned, and i've located the moaning noise to the back, not the front which i originally thought(sunroof being open can do weird thigns with sounds......). I will be replacing those pads asap, probably this weekend. I just replaced the front pads, and when i did that nothing seemed ary. I cannot afford new calipers at 250 bucks a peice, so i'm praying that isn't the problem, if it is, i will be looking for rides from people for a little while. No wheel has excess heat, and nothing had begun dragging noticibily again, it was just that one incident. But, things dont normally cure themselves, so i'm sure my problem will re-appear. I hope it stays gone untill i have the $$ to fix it though
Ryan

#6 03-12-2002, 05:14 PM

Your `83 300SD either has Ate, Girling or Bendix calipers
for brakes, and in various combinations front and rear
paired. From the description of the car's driving characteristics
it displays symptoms of a seized caliper or a faulty brake
line. One indication can be increased brake dust; excessive
heat another at the suspect wheel. Given the age of the
vehicle, provided the brake system has not been checked
thoroughly nor regularly serviced on time, to have a brake
caliper to disfunction should not surprise.

At or about the model year of 1983 Mercedes began to use
significantly more Bendix brand brake calipers. The chances
are good, very good, that you have combinations, in pairs,
to include Bendix brake calipers. It's not for fully certain that
you would have Bendix, just highly likely. Now there is nothing wrong with a Bendix brake.

Ate is a German brake. It works on a slightly different set
of engineering ideas than the others. Ate is well-known to
give that legendary Mercedes-like stopping power thus to
join the the other two in the class of superior brakes.

Many vendors will not rebuild brakes today. A variety of reasons
bring this about but safety, cost and liability concerns are to be
included. Therefore, if you have a seized caliper you may need to
purchase a replacement brake caliper, and in a set of pairs.

Since brakes either work perfectly or you have no brakes, I'd
see to this issue at once, and if replacement brake calipers
are to be done, too, I'd go with Ate. New brake lines are also
easy at such a time.

When one considers that brakes and steering comprise the basic
fundamentals, if one has no brakes nor steering one has no car,
essentially.

vwbuge · #7 03-12-2002, 07:29 PM

$250 a piece for calipers?! Where are you shopping? My '85 has ATE brakes and I can get the calipers for under $100.

lrg · #8 03-12-2002, 07:58 PM

RG5384,

Check your flexible brake lines. They run on each wheel from the solid brake line to the caliper. When these begin to fail it almost always starts as swelling on the inside that constricts the flow. You can easily push fluid in to the caliper but the pressure doesn't release easily so the caliper appears to be sticking slightly. These are cheap and easy to replace so if they are at all hard and stiff I'd replace them first. It's also a good excuse to bleed all the brakes properly.

diesel don · #9 03-13-2002, 01:08 PM

I need to address two sticking calipers on my TD soon. My question to you brake guys is this:

What exactly are Bendix calipers? How do you identify whether or not you have them?

Also, in rebuilding a caliper (i have the kit with seals, etc), what type of lubricant does one use?

Thanks

Don

JimSmith · #10 03-13-2002, 01:33 PM

diesel don,

Bendix is a manufacturer and the caliper itself will have some identifying brand marks on it. If you want to know what kind of calipers you have it is likely easiest to pull the wheels and look.

One of the most common reasons for disc brakes to "stick" comes from the wear on the seal you have in your kit. Wear can come from age, dirty brake fluid, corrosion of the piston and other things.

The seal is a square cross section "0" ring, and it is the only part of the braking system that pulls the piston, and therefore the pads, away from the disc when you take your foot off the pedal. It does this by the design of the piston to cylinder wall clearance and the selection of the seal material.

The seal is captured in a groove in the cylinder, and has a high coefficient of friction against the piston. The travel of the piston by design is very small, so the seal gets deflected or distorted when you step on the brake pedal. When you take your foot off the pedal, the seal provides the spring force needed to push the the piston back far enough to release the clamping of the disc by the pads. If the seal wears the design conditions no longer exist and there is nothing to pull the piston/pad away from the disc.

The result is a sticking brake. The most successful fix is to put a new caliper in, as any honing of the cylinder or other metal removal operation on either the piston or caliper cylinder will upset the seal dynamics, making the seal less likely to be able to do its job.

So, if you take your caliper apart and there is corrosion on the piston due to running too long with worn pads (sticking out too far) and being exposed a corrosive environment, you will be best served with new calipers. If everything is pretty clean and moves freely, a new seal is needed and that may work fine. Your kit should include some other protective parts, like the rubber bellows and some other seals. As for a cleaning fluid during this job, I would use brake cleaners and brake fluid. I would only use brake fluid as the lubricant putting the parts together as this is the only fluid that is supposed to be present at the piston to caliper bore seal under normal operation.

Hope this helps, Jim

diesel don · #11 03-13-2002, 09:58 PM

Jim:

That is a huge help as I'm tackling this problem tomorrow. Thanks for spelling it out so clearly. It seems as if each new job is a mountain to cross until actually accomplished. Will print it out and take it with me.

Don

#12 03-14-2002, 11:14 AM

For the purpose of safety, and safety alone, DO NOT rebuild the
brake calipers, REPLACE with two new calipers. Not everyone
has the skill to correctly rebuild a brake caliper and that is why so
few shops do it. You may not care about your well-being nor
the value of your car, but faulty brakes could injure someone else
and cause them losses. Again, it takes knowledge, skill and real
insight to restore old calipers, so do not try to play expert with
this equipment. Buy brand new calipers in pairs and be safe.

You have been warned.

JimSmith · #13 03-14-2002, 01:30 PM

TXBill, D Norton, and most of all diesel don,

Rebuilding calipers, if there is anything more than a seal change needed, is likely out of the skill range of anyone but a brake specialist. And, unfortunately, most calipers are ignored until, when you take them apart, there is more than a seal to change needed to restore them.

Recognizing when the job turns to replacing several pounds of scrap metal with new parts from changing a few grams of rubber seals, is probably the big judgement call in this task. All I can say here is if there is visible damage, lean toward the scrap and replace decision. But the seal change operation is clearly a job within the skill level of an aware do it yourselfer if all else is in order.

If you look at the Mercedes-Benz shop manuals for the earlier cars (like my 1975 240D) they include caliper rebuilding instructions, which are limited to seal replacements. They involve before and after checks to verify the fix actually fixed the problem, with special tools, and a road test. Most of us do not have access to the special tools, and will rely on the road test. You can do this in stages as well, to reduce the risk. Like check brake function with the system back together in the driveway, then at slow speeds and then at more normal speeds. If this repair fails, it should show up on the driveway test. Leaking fluid, sticking brakes or no brakes (not sure how replacing seals can do this) should show up before you put the wheels back on, with the car jacked up.

The reason you cannot remove metal to correct gouges, scrapes, general corrosion, and so on in the bore, or on the piston, is metal removal, no matter how small, changes the design geometry of the interface between these parts and the seal. Once this is out of the range of the design, which most instructions do not disclose, including the MB shop manual I have, the brake function is compromised. The brake may leak fluid, limiting braking force, or, more likely, it will stick again.

So, if all you are doing is changing a worn out, rubber seal, I think the job can be successfully performed by a reasonably aware do it yourselfer. Knowing the brakes are a safety system, I, diesel don, or any other individual doing the job will take extra care doing the job.

I used to think the brakes were so important I only let the dealer do the brake work. Then I was severely disappointed by sloppy work on something I held so important I did not trust myself to do, and I was forced me to rethink my logic. Confronted by the data, I concluded my brakes are more important to me than they are to anyone else, so I learned how to work on them confidently.

I now only let the dealer or anyone do something on my cars that either requires a special tool that costs as much as the repair itself and is not a regular repair, or is something I aknowledge is beyond my experience and is also not a regular or repeat item. These "rules" still keep my dealer, and a few other mechanics in the area, busy on occasion. As I get older the rules change a little and I will pass a job I used to do to a mechanic just because I do not have a garage anymore and have to work on my driveway, and I don't feel up to the task physically, like in the winter.

Some advice to diesel don for this job, and most of the jobs that expose the insides of machinery, is "Cleanliness is next to Godliness" which was passed on to me by a nuclear submarine machinist with about 40 years on the job. Dirt and the like, known as foriegn material, is the enemy of sliding, precision fits.

So, I do not agree with D Norton's ominous tone, or his blanket statement, but I understand the caution. The kit comes with all the seals and other soft parts you need, and if you limit yourself to taking out the old, keeping things clean, and putting in the new, the job is doable.
If the seals do not fix the problem you will have the same problem when you had when you started, when you think you are done, sticking caliper(s). Unless you make a serious mistake, like leave a part out, you should not have any new problems as a result of changing the seals. In any case all this should be apparent when you test in the driveway. Good Luck, and I hope this helps. Jim

#14 03-14-2002, 07:10 PM

For "Bill," the forum Diesel Moderator

Firstly, let me put you at rest. I will find another place to rest my
head on the `net. You can close my "user" a/c with mercedesShop
as soon as you have read this post. We part as friends and why
not? We both like mercedes diesels.

I am totally unaware of parts sales and tech help available via this
mercedesShop vBulletin `net site. I just plain never knew about it.

In Europe today, repair garages accept brake calipers for rebuild. I'm not aware of exactly how it works entirely but repairable
brake calipers are forwarded to repair facilities wherein serious
experts under the highest cleanliness standards work with
layers of failsafe standards to remint brake calipers. Perhaps
they devote so much energy to this activity due to the autobahn
system which permits speeds in excess of 150mph but the average is 90mph, according to the ECU. USA cars use the exact
same Ate, Bendix and Girling units, also Brembo (later). No
similar system exists for officially supervised brake caliper rebuild in the United States. Since we have no similar system in place like
the Europeans, the only certain method to guarantee the inner
workings and hidden mechanisms of those MB supplied brakes is:
1) to purchase replacement new; or, 2) rebuilt from Caliber Motors in California, an MB dealer, who is the only MB dealer in the US who offers rebuilt brake calipers done by MB and carrying a warranty by MB. Please do reconfirm all of the above. You must.

The fact that various US independent MB shops can obtain seal kits to rebuild brake calipers does not guarantee that they would know what they are doing. When to toss a piston or to call a ridge
out-of-round for the squared accordian seal involves more than
a naked eye or "feelings." Dust and dirt must be eliminated even
to the extreme of using denatured chemicals; oxygenous matter
held behind the piston may never be expelled through the M/C-----well, on and on and on. Many shops have no such ability, no such committment nor awares to properly succeed at this task. In fact, used calipers of a similar brake manufacturer would be a better idea if an owner couldnt afford to purchase new calipers.

In addition, the mere fact that seal rebuild kits are sold may only
imply that someone has their thumb stuck on the sales button.
It is much the same as someone selling ammunition but no firearms or controlled substances but no syringe. Better to rethink
this entire line of argument. This is a tautology; circular reasoning.

The internet is a strange place, Mr Moderator. One can say anything that one wants to and without fear of too much accountability PROVIDED you dont say anything that hurts someone or casues them losses. I realize that additional rules are agreed upon at the registration of mercedesShop and the vBulletin system. I have been here for exactly 3 days. I am
responding to you as the Moderator for your plead for an answer
back and this at my first having laid eyes upon your query. BTW,
nice to meet you, too.

Faulty brakes can kill, Mr Moderator. It is a safety issue. The reason for an addendum repost to this thread was to provide
an additional evidence from myself for all potential lurkers that
I take no responsibility and can take none for any party who
attempts to improperly repair their brake system and as a result
of anything read. It did alarm greatly to see a lister say, in effect,
that he was going to go do his own brakes soon, yes, it did. I'm
sure that some of the estimated 125 vehicles that piled up today
on I-75 North in Ringgold, Ga, will be inspected for their brakes; very many of the 176 cars that piled-up on I-10 in 1995 in Mobile
Alabama, were later examined for their brakes, too, or so I read.

Mr Moderator, there are a few Federal statutes that happen to
address these types of specific subjects, if you would know how to care to learn to peruse these matters. I would have thought
that you, as a Moderator, would have already done a thorough
checking of such, especially in re safety issues.

It disappoints that you do not know how to care for my various
posting commentaries Mr Moderator, yet I accept that you have
the right not to like them. I have reread some of the content of
those posts, especially for accuracy, completeness but not for
appropriateness for this venue. No emendations will be given you.
Your comments that I am opposed to the DIYer is an unsupported
comment which is unsupportable. How would you know such a
thing? I have a mere dozen posts yet you condemn? If you go
back and take a second look, you'll see several items that confirm
DIYer experiences.

I must say, Mr Moderator, that of all the things to call attention to
for an infraction of list culture, it seems to me that brakes would
have been almost at the very least likely to expect any call-down
at all, especially given the conservatisms I wrote. Those silly
rebuild kits cost somewhere between $11. to $19.---- hardly
enuf to make a list vendor insolvent. Also, if it does threaten a
long cherished notion of some that brake caliper rebuids are a
serious buisness given over to competent workmen: Good! It
might save their life. It might save your life, too, Mr Moderator.
Who knows? They guy on your tail next time may have rebuilt
his own brakes...

Anything further dispositions might be best handled via direct
emailings. I have no issues with your future contacts via that
method. Unfortunely, the matter may seek for further discussion.

Good luck Mr Moderator!

psfred · #15 03-14-2002, 08:00 PM

I have replaced the rubber components in brake calipers many times. It is very easy, and the only thing that can go wrong is that you cut the piston seal putting the piston in.

I have never re-condidtioned pistons or bores, and would not for the simple reason that any polishing or piston or bore will ruin it for further service.

Don't mistake rebuilding a caliper for repair/reconditioning -- I take rebuilding to mean replacing wear parts (seal and dust boot, heat shield, springs) ONLY. Any corrosion or "crud" that cannot be removed with a cloth and brake parts cleaner condems the caliper for further use.

Restoring pistons cannot be done -- new pistons will be required if damaged, and must be oversized if the bore in the caliper is machined. The bores and pistons are chrome plated, and the plating must be renewed for the caliper to work correctly. It should be obvious this is not a DYI project!

Ryan:

The low speed growling is a sign the rear pads are shot -- replace them pronto. If there is a palpable ridge at the outer edge of the rotor, replace those, too -- $45 apiece, cheap at the price, else the pads will collide with the retaining spring on ATE calipers, jam, and seize the pistons in the bores. Ugly.

I stick with MB pads, and please, please, break them in properly -- no hard stops for at least 50 miles of city driving -- else you will melt the adhesive, glaze the pads, and have crappy brakes until you replace the pads again!

Peter

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