I have a very well-maintained 1986 300SDL which I love.

My brakes were working, but squeaky. An independent mechanic recommended turning the rotors and installing new pads. I did so, to the tune of $280. When I got the car back, the brakes were still squeaky, the steering wheel shimmied when I braked, and every now and again, the brakes moaned B flat above middle C.

A week and a half after this brake job, I lost my brakes on the highway. The pedal went to the floor. I regained about 5% of my brake power, enough to safely get me off the road, but pumping the brakes did nothing.

I took the car to the local Mercedes Service Center, and asked for a thorough inspection of my braking system. The result: four rotors ground below minimum spec, and two failed rear calipers.

My question: How likely is it that the rear calipers failed at the same time, showing no prior warning (obviously, if the calipers had been leaking or cracked a week prior, the mechanic should have told me). The independent mechanic insists that the age of the car is at fault.

I happen to think that the calipers were put in incorrectly. I can try to force the original mechanic to pay for the $1200-$1500 dollars worth of repair, but not if it's not his fault.

Any advice would be much appreciated.

Thanks,

Rachel

Jeeze, it is hard to make factual judgements, but I will share my thoughts. I doubt any post you get will help you financially, but it may help you detect BS if you see or smell it.

The shop that did your brakes was obviously incompitent if they turned rotors below minimum thickness. This says alot about them. If you took it to the local Brakes-R-us instead of a reputable shop, shame on you. One of the two shops is obviously not reputable. Pick up one bad rotor and have it measured by a third shop (this is so simple, they should not charge you anything), and now you know who you can trust. Stop doing business with the liar immediately, even if they offer to fix their mistake for free. Brakes are important to you (and me)!

One reason for a minimum thickness on rotors is there needs to be a certain mass of metal to absorb the frictional energy of braking. Too thin and they overheat and warp too. If they overheat, it can transfer heat to you caliper and harden the rubber seals in the caliper. I don't know why it happend to the rear, since the front does most of the work. Maybe they were already old and this agravated the problem. Also, maybe the the heat "boiled" the brakes fluid causing air and loss of braking. You would have to be doing some pretty hard braking, even with the thin rotor condition to cause this problem.

Another posibility is that the calipers are old, gunked up and dragging, which is causing premature brake wear. In this case, the original shop should have noticed this as well, but was not caused by them.

So, you need to do some more research with the shop to really understand what they have found wrong, not just what part is bad.

Good luck!

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Deezel
87 300TDT
150,000 miles

...another possibility is that with the rotors being so thin, the caliper pistons just went too far out, and once past a lip that I am sure has developed over the years, wouldn't 'go slack'...this heated the poor little darlings up to the point of failure. The thing that aggravates me about this whole thing, is that the rotors for a 126 are cheap! (as in when you buy some, not in quality) . Grrrrr!
Your mechanic get my putz of the month award!

I just reread your post...12-1500 dollars?? I hope they wash, wax, and clean your carpets too for that.
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03/83 300D 184k
07/73 280 160k

[This message has been edited by Larry Delor (edited 04-04-2000).]

I think that both of the statements above hold true in this case...We don't even own a brake lathe and do not EVER turn down rotors. Once below min, they will overheat quickly. The reason for the rear failure is the thin rotors cause the pistons to ride in a spot where years of buildup has produced rust, when this passes the seal, it will cut it and the seal will leak...

Sorry about the trouble.. Make the other shop pay for the damage and have the dealer repair it.


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Benzmac:
Donnie Drummonds
1981 280GE SWB
1987 16V
ASE CERTIFIED MASTER AUTO TECHNICIAN
SERVICE MANAGER FOR 14 BAY FACILITY
MERCEDES SPECIALIST 8 YRS
PARTNER IN MERCEDESSHOP.COM

I agree with not turning rotors, but some people stilllike to do it.

Concerning the piston traveling out too far after the rotors were turned, I thought about that too, but if (and I guess that is a big if) they had put new pads in, that would have more than compensated for the loss in rotor thickness. Either way, we agree that that there has been some bad brake maintnence going on!!!

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Deezel
87 300TDT
150,000 miles

THE REAR CALIPERS USUALLY FAIL IN THE MANNER YOU DESCRIBED BECAUSE OF A BAD MASTER CYL. VALVE,THE VALVE STICKS CLOSED AND WON'T ALLOW FLUID TO RETURN FROM CALIPERS ,BRAKES DRAG,PRESSURE BUILDS,HEAT,SMOKE, FADED PEDAL,EMPTY WALLET.
IF YOU HAVE NOT REPLACED THE MASTER CYL. YOU MAY BUY EVERYTHING AGAIN!!
M.F.

After you get the car back from the dealer, drive it on an open highway at full speed for a while (5 minutes?). Find a safe place to stop and turn off the engine. Check the temperature of the wheels. If there is an overheated brake, you can smell it. Touch the center of each wheel with caution (don't get burned). If the wheel is too hot, you may have a problem. I cannot tell you how hot it should be, but you should not smell burning.

If 5-minute driving is not long enough to surface the problem, driving another 10 or 20 minutes more (open highway with little or no usage of the brake). If there is a problem of brake over heating, you should be able to tell now. The problem caliper is much hotter than the rest.

David

[After you get the car back from the dealer, drive it on an open highway at full speed for a while (5 minutes?).

Please don't do this on US roads. There is absolutely no reason to drive fast to check brakes. If you are worried about dragging a good drive through the neighborhood with a bunch of stop and go is the test. Driving fast without applying the brakes won't test much other than your driving skill and recklessness.

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Steve Brotherton
Owner 24 bay BSC
Bosch Master, ASE master L1
26 years MB technician

Every rinky dink mechanic wants to turn down rotors - more labor more money, especially if it is a woman from Harvard, no offense intended just the truth. I used to work for a franchise.

Was this a recommended mechanic? Unfortunately, as described above, mechanic is will depend on how much $$$$ you get.

I'd ask for some mulah, then I'done bad decision led to another. I think you have a strong case to get some money back, but normally these things are hard to prove and depending on how honorable the fualty go to a deaeler next time while you ask around for someone reputable closer and maybe cheaper. Dealers usually guarentee their work for a longer period of time. I would not take my Benz to one of those Franchises that you see on TV, you know their names.

Just my $.02, but what do I know?

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'89 420 SEL
'90 300 SEL
'84 300 SD (sold it)

I do value every Steve's commant very much. I am sorry if I misleaded anyone (April fool passed already) last time for telling you not to use the brake on a highway. Let me try to express my idea one more time in one or two sentenses to see if that helps or makes it worse.

If the problem is in the master Cyl as M.F. suggested, the problem of no braking while driving on a highway may happen again. My suggestion is to check the brake from time to time just to be sure that the brake fluid do not get to the boiling point (assuming dragging is the cause) during highway driving as it failed last time. Safety is the key.

David



[This message has been edited by be459 (edited 04-08-2000).]

Well, boys--

You're all awfully helpful. And this situation keeps getting worse and worse. I had the car brought back to the independent mechanic (not a franchise) who had first worked on it so they could fix any of the damage they had done.

They had insisted the front rotors weren't too thin, but replaced the rear rotors and calipers. I paid for the rotors. I also purchased an original Mercedes master cylinder and sent it to them to install; the master had broken when my calipers went.

I went in to pick my car up yesterday (and the frightening things I saw there, I can't even begin to tell you).

Now my brakes are usable, but I'm out $700, and I should still replace the front rotors and calipers.

New problem: the car no longer shuts off after removing the key. I know it's a vacuum leak, but could it have been caused by this lousy brake job?

Thanks again,

Rachel

You car not shutting off is indicative of a vacuum problem. There is a vacuum switch connected to the ignition switch which is responsible for shutting off the engine. If this switch goes bad or is not connected, your car won't shut off.

I am really sorry for your predicament. I am surprised that you got this kind of treatment from an independent. My motto is, "If you burn me, you can only burn me once, once". I think that was from a movie. Anyway, I would take it to a dealer until you get some suggestions from users in your area. A decent mechanic would at least eat the labor costs from a mistake, but if they make no concessions, run for the hills.

When it comes to a Benz a dollar of maintenence is worth a $1,000 of repairs. Cutting corners only causes more headaches.

Then again, what do I know?


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'89 420 SEL
'90 300 SEL
'84 300 SD (sold it)

I hate to digress, but there are a couple of things I would like to clarify now that I read your original message more carefully.

#1)How many miles does the car have?
#2)How long have you had the car?
#3)How many miles did the car have when you bought it?

OK, enough with the 50 q's, the point is that if you are a new owner, there is a chance that one of the prior owners replaced the front calipers and wheel cyliners a while back while the rear ones could have been the originals. You would know this by checking former records or, or of course, if your are the original owner.

If that is the case, in your mechanic's defense, it is possible that after he put new pads on the back with the old cylinders, the cylinders overpressurized and ruptured (happened to me on a classic american car). It would have not done anything to the front because they were newer.

It is very possible that this is the case because the front breaks wear out twice as fast as the rear, hence replacing the fronts in the past is not all that out of the question if your car has more than 100k miles.

There is also a distant possibility that he put on the wrong pads. The distance between the pad and the rotor have to be accurate to avoid overpressurization. Slapping generic pads on old brake equipment could be a disaster. It is also possible that they did not turn them down properly as well.

I first read your post in the middle of the night, but after thinking about it, there are a lot of factors that need to be considered and researched to ascertain who is as fault.

My best take is that you are a new owner of the car (less than 1 year) and your mechanic tried to save you money by taking a conservative inexpensive route, and due to the age of the componenets, cause addition malfunction. Unfortunately, this is common for new owners of used cars. Don't get too discouraged, only a small price to pay in the long run to enjoy the finest of automobiles.

....That'll hold true, if I knew anything.



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'89 420 SEL
'90 300 SEL
'84 300 SD (sold it)

Matt,

You're right. I've owned the car for a year. I bought it in very good condition from the original owner. It's now in beautiful condition, and certainly doesn't act as though it had 250K on it.

The problem seems to be the number of things that have gone wrong at this independent shop. Calipers, rotors, master cylinder. The connector for the swaybar is cracked. My main vacuum line (that runs from the master cylinder drum to the engine block) is cracked right at the master cylinder. These things were all working perfectly 3 weeks ago. Just a few too many coincidences.

Because of the cracked valve in the vacuum line, I can't turn off the car. I'm getting an ulcer.

By the way, what is the technical name of that vacuum line? And do you have to purchase the entire thing, or can you replace valves in it?

Thanks,

Rachel

Hello Supergirl/Rachel,

For brake (and ignition)repairs, it is always best to stick with factory original parts. As a general rule, aftermarket parts tend to squeal and pulsate due to (different) composition and other technical stuff.

May I recommend that next time try going over to Somerville to the dealer and ask them for an estimate. "An informed consumer is a smart consumer".

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