Sounds like you need a lot more than pads.

Sounds like a leaking master cylinder and/or sticking rear brake caliper/failed hose.



You need to have someone who knows what there looking at check out the brakes. How were the seals around the pistons? Could you depress them without to much effort? Are the hoses original, most likely they are.

If it were my car I would throw a new master cylinder on it, plus a set of hoses all around and flush the sytem with some ATE DOT 4. Luckly rear calipers are cheap so if I suspect those I'd throw on a pair, maybe some discs and do the bearings while I was back there since they have probably never been touched.

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1999 SL500
1969 280SE
2023 Ram 1500
2007 Tiara 3200

Re: "Sounds like you need alot more than pads..."

That would be my luck! It really would. What I really need is to win a big lottery and buy a brand new car. - but I dont think a new one would be built as good as my W126.

I would love to do all of that work if I were a millionaire. The car will have to just set. I just had to spend almost $400 to have the fan bracket replaced on my Lexus (which was a sudden failure that I was not planning on having to do, because I need motor mounts on that car and I had been planning on using that money for that), so I cannot afford another costly repair on this or the Mercedes now... I am quickly chipping away at my hard earned savings account and this Mercedes car is also in dire need of tires and an alignment. It seems like everything is happening at once and its really starting to bum me out. Just had to rant a little there.

It looks like the brake hoses have already been replaced not too long ago. The PO was really good about maintainence on this car. Its just the pads were wearing when I got the car and I guess got worse when the right rear brake started sticking some. There were actually still some pads left on them, but they were worn quite low.

The seals around the pistons looked fine and they were not too hard to depress and we were able to finally get the pads on. My dad has changed brakes hundreds of times on our other cars over the years, just never on any Mercedes. Last time I had to have the brakes replaced on my other Mercedes I had, I took it to a shop, but they had it forever.

You said "leaking master cylinder"... do you mean leaking air or fluid? I dont see any fluid leaking and the level in the MS reservior is full and fluid is very clean. Bearings too? I dont hear any whining or anything... is that something that could wait? They may have been done already for all I know.

I had the sticking RR brake for a few weeks, but never had an issue with the brake pedal going low. It was fine that day (pedal was normal) but after driving 5 miles on a highway without needing the brakes, when I depressed them, they went very low, but the brake warning light never illuminated. I had to use the brakes 4 more times and it felt the same way... it felt like the rear brakes were not working at all. When I would stop, the back of the car would bounce.

I thought I would try new pads first, then a master cylinder if necessary, but I am not buying a MB one - $120 - puh-huh . I found one for $60 if need be, but it will be next week before I could replace it. I have had the worst luck with brakes on my cars... my old Pontiac is currently in need of a master cylinder and I bought one (for a whopping $17!), but it was the wrong one, but the one I need is also $17.00 and its much bigger than the MB one. Funny how MB parts are so costly and how I always have such bad luck with cars. I was hoping it would be awhile before this car needed anything major. Thats what I get for hoping.

I guess I will replace the other pads tomorrow and see what happens and replace the MC if I need to later in the week. I hope not though. The MC itself is very clean and actually looks almost new, but under my hood overall looks very clean - not like it was just cleaned, but like a "cared for" clean- which is good I guess.

Thanks for the tips/info.

Also, if the master cylinder was bad, wouldnt the brake warning light illuminate?

Sounds like you can't afford the car, sell it and bank the money.

Not having experianced the problem, and since you report no external brake fluid leaks it sounds like an internal master cylinder leak. But it could be vacuum related to, further diagnostic work is needed.

__________________
1999 SL500
1969 280SE
2023 Ram 1500
2007 Tiara 3200

... I could never sell it for what I had in it (I only gave $2000 for the car, but another $500 for shipping, then another $300 in taxes when I bought it last year) and I am not going through selling another car, then buying another, then paying state taxes on another car... I am going to drive this one until the wheels fall off.

I also guess its better than a $400-500 car monthly car payment though on a new car and soon the other car will not be mine... I am giving the Lexus to my mother. The car is paid for though and I guess after these repairs, it would be OK. Its just everything is happening at once (with my other costly car repair). I have a good amount of savings in the credit union, (I dont mean to sound like I am in the poor house) but with the way the economy is now, I am not keen about throwing money out on unnecessary repairs, ya know? Not to mention I am stingy.

I guess I will shell out $60 for a new master cylinder, $60 for 4 new brake hoses and however much more for calipers, quarts of dot 4 brake fluid and whatever else decides to break with the way my luck has been. I guess I cant complain, I have not had any problems with this Mercedes at all until now.

Lastly, where are you buying your calipers at? $85. each here on Fastlane and even more at places like Autozone... like $110 to $150 each. Thats not cheap to me. "kits" are available for like $30.00, but just looks like little seals.

IMHO changing the brake pads on Euro cars must be one of the most simplest jobs.

The 4 wheel disk brakes on my 1967 Fiat 125 sedan were the same design as on your W126 - as on BMW's and a host of other cars. The rear disc pads off an early BMW 7 series are the same pads as used as front disc pads on some BMW motorcycles.

Standardization - what a glorious thing. Try and find some Japanese cars with common parts.

Don't let your rear pads get less than 25%. You may end up with caliper problems. You may have fallen victim to this.

Easy indeed. We did the other side (left rear) this evening when I got home from work and it was easy as pie. It was not stuck tight like the right rear one was and the pad on the left rear was still like new whereas the right rear was down quite a bit.

If you're certain that the RR brake hose is OK then the RR caliper either needs to be rebuilt or replaced because it isn't releasing properly. Merely replacing the worn brake pads isn't addressing the real problem.

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Fred Hoelzle

I dont know. Im not certain about anything anymore. I drove the car today for the first time since the pads were replaced and the brakes are working fine now.... nice pedal and powerful braking. Also, the RR brake does not seem to be sticking at all now.... I dont smell it and the car will roll freely now, whereas before, it was held back a little.

For now its fine, but it may go bezerk again next time I drive it. I guess if so, I will replace the hose and rebuild the caliper. Seems cheaper to rebuild than to pay $85 for a new one?

Thanks!

dude...it's the master cylinder....rocky racoon gave you good advice....replace the master cylinder. THEN replace your rear brake pads (both wheels).

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1990 560 SEL- "Goldielocks"
1984 300SD TurboDiesel- "Ole' Blue"

Thanks, but I am confused... did you not read my update? The brakes are working perfectly now. Does that mean the master cylinder can still be bad even though the pedal is up now, firm and perfect working brakes?

Does a master cylinder thats bad work fine? Also, wouldnt the brake warning light be on?

Rocky Racoon also said for me to just put on new pads and I could get lucky... seems as though... as I said, the brakes are working fine now.

Just wanting to update...


Thank goodness, it turns out I didnt need anything more. New pads, brakes good as new.

Actually it wasnt the master cylinder... new rear pads, brakes as good as new. Good pedal and powerful stopping power and the RR brake is not sticking anymore. Thanks for the info though.

I just wanted to update incase anyone else has this issue. Oh, also to those that said these were easy to replace, you were right. Easy indeed. Thanks again all.

Make sure that you spray you disc librally with anti-squeal while you have the wheel off. Spray both sides of it, making sure you turn the disc to make sure that you spray the part that is under the brake pads. Also, make sure that you take note of how the spring-clip fits into the unit before you put the pins back in. Good luck
JD

It might have been something as simple as the worn brake pad tilting in the caliper and binding up, causing it to drag and wear further.

Just one more reason to try to prevent the pads getting below one quarter of their new thickness!

As to parts to replace first, I was always taught to start with the most likely causes of a problem, especially when you have one that is already obviously broken or worn out.
If I were to be working on this, I would be looking at a possibly rusted/worn caliper on that corner as well, before I would install a new master cylinder.

In applications where there is a sliding caliper, greasing the slide pins makes a world of difference, but I seem to remember (it's been a while since I've had to do rear brakes on my cars) that this is a fixed caliper, so not an issue here.

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-Josh
Testing the cheap Mercedes axiom, one bolt at a time...