D Norton,

I hope you rethink your decision to drop off the board. While I have disagreed with some of your previous posts, I recognize one of the better features of this forum is the built in checks and balances on the information you get here that comes from the variety of people with their many backgrounds that participate. No one wants to drive away a potential source of good information just because they don't agree with how a point is being made.

Data is data and the only thing that can color it so someone can "dislike" it is how the data is presented. We all need as much data as we can get, so we have to learn to provide data as we would like to get it, which is efficiently and effectively. In general, the people on this forum want to know how to do something, which means they are most receptive to data that is presented in the form of direction to finish the job they want to do. They are already disposed to do the work, and live with the consequences they are aware of, which is usually believed to be paying someone more money to clean up any mess they make of it. If someone has data that is critical to safely completing the job, we all need that data desperately. If it is presented in a way that can cloud its true meaning, it will, and the data is not recieved.

I am supposing something here regarding Bill's perception of some of your past posts, but it reflects my impression too. The tone of your posts has been less to provide guidance to someone trying to do something themselves and more to admonish them for considering it. I think from the time and care you spend to get information to those seeking the information would be more satisfying for you personally, and those reading your posts, if the information was presented in the perspective of how they are looking for it.

The topics you have posted to, and the information you have given, hint at a vast experience with a lot of the technical details important to why these automobiles are such great engineering and manufacturing achievements. I for one hope you do not drop us out of frustration, but learn to communicate with us so we can get to share some of your experience. Hoping you change your mind, Jim

David:

Your attitude has pissed me off on more then one occasion, but like the others, I'd hate to see your knowledge dissappear from this forum because a comment was blown outta proportion.


If you learned to word your posts less like a Dealer Mechanic talking to Ms. Yuppy and more like that of a mentor (helpful warnings are great, but not this "Take it to the dealer" hoohah) then you'd be fine here.

even the best driver in a new s class may not have been able to avoid the terrible mayhem today on I75 but all i can say is if i had my choice in that situation i would be in a benz.

the mb brake system is imho one of the best in the world and as mentioned the condition of the caliper itself is paramount if you consider rebuilding or replacing.

I agree 100% with 84300DT. Maybe because we own the same model year Benz... (?)
I know that my car is capable of locking up both rear tires, and still stop straight and true, and this is without ABS.

I just had my shop put on new rotors and pads front and rear. My old rotors were rusted and/or worn to the point that my car needed them replaced to pass PA state inspection. Anyway, wow, now I have brakes, and I mean serious brakes. (My car has always stopped better than my wife's Subaru Legacy, but Subaru brakes are weak, and give a very uneasy "graunching" sound during heavy braking.)

The old rotors seemed to "grab" a bit earlier in the pedal travel, but if I get on the pedal a bit, I now have nice linear braking power. I was afraid to use full braking for the first 200-300 miles or so, but am working on "braking them in"...

I did want to say, in closing, that most mechanical work is beyond where I feel comfortable going, both for time and laziness reasons, but I value all of the insight I have gained into automotive science from the many selfless experts that have blessed this forum with their wealth of knowledge. So many people have answered all of my questions over the last three years that I've made this forum my own personal "hiding place" on the web.

I do love God for all He has done, but if "cleanliness is next to godliness", you should look elsewhere to find him because my poor hands look like diesel oil thats traveled 50k miles.

Good words of caution on the brake area of repairing MB's. As I removed my first "stuck" caliper and tried to free the piston I became convinced that the job was beyond me. In fact, I believe that the caliper is beyond repair. I couldn't budge the piston inward with two monster clamps, and I couldn't budge it outward with compressed air.

I therefore called around and found another wagon which was being parted out. I removed all four calipers from it for $120 and went to work. The two front calipers were 2 years on a rebuild and had brand new pads in them. The two rear calipers were used and I found one to be usuable and the other to be stuck. Since I only needed one rear caliper (my other one was functioning well), I just put the working one on my left rear.

After putting new pads in the rear and bleeding all four lines I have a couple of questions:

1. Why can't I get my pedal as firm and awesome as my 300D? The brakes feel good and I'm confident in them (drove 30 miles in traffic), yet they don't have that awesome feel that some MB's have.

2. I used a right rear on my left rear because there were only two noticeable differences. One was that the bleeder screw ended up near the bottom rather than the top and the second was that the brake hose ended up being 1/2 inch higher. Seems to function well. Was that stupid or have you heard that it can be done?

Don

Don,

Sounds like you have been pretty busy! I know about that grime that just won't wash off, you have to let it wear off your hands and grow out from under your fingernails. And so far, my wife finds the stuff very unromantic. Big problem for my hands on the weekend as I am usually inspired to scrub a lot....

The bleed screw needs to be at the top of the chamber to allow you to bleed all the air out.

Also, I would be very reluctant to change one caliper on an axle, and I would not mix brands and model/production variations to ensure equal and effective braking across the axle. I would be less concerned with the brake line connection location, provided it is not kinked or strained over the travel of the wheel.

You should be able to get at least the same pedal response as you had before you started the job. Are the calipers the same brand and production models? If the bleeding (brakes, not hands) does not address the pedal feel, I would suspect the bleed screw and supply line configuration are not allowing all the air to escape, leaving you a small bubble to compress.

I cannot get to one of my cars or manuals to check this for a few more days, but I thought the calipers were the same on each side, and to deal with your bleed screw issue, one side had the caliper "behind" the wheel and the other on the "front" of the wheel.

Well, you have your "hands full" on this weekend. Good luck, and hope this helps. Jim

Diesel Don,

How did you bleed the brakes? On my 1984 300SD, I tried to bleed the brakes using the rubber hose/brake fluid-in-a-jar method. After two hours of trying, I still had a soft pedal. I got a Mitty Vac and bleed the brakes again. It took a lot of bleeding. Now I have some really good brakes. I would say that bleeding brakes on a Mercedes is much more difficult than other cars I work on.

As far as your right/left caliper swap, I noticed that in all calipers and wheel cylinders that the bleeder valve is on the top. I think that the air in calipers accumulates on top. When you flip a bottle of water over you can see all the air going to the top. When you bleed a flipped caliper, no air would come out since the air is trapped on top. You would think that you would have bleed the system, but you didn't.

I must admire your idea of a flipped caliper. It sounds like something I would have tried also. If you want to experiment, you take the caliper off the wheel, flip it over, bleed it, and put it back on. I think this will work for you.

I'm a DIY'er and have repaired my brakes on both my BMWs, Porches and Mercedes for the last 15 years with no shop experience and no failures/problems. It's straght foreward and easy. You put it back together the way you took it apart acording to the directions that come with the seal kits. Quite easy in my oppinion. The only real safety issue is that you MUST replace the rubber whenever the caliper halves or pistons are dissassembled. Cleaning the parts is easy and straghtforeward. If the cylinder or piston is dirty, use a fine steel wool to remove the rust deposits, as it isn't hard enough to damage the caliper's metal. These deposits only result from not changing the brake fluid often enough (MB says yearly) because it's hydrophylic.

The only dissadvantage with this procedure, is that there is no outlined procedure for it in most manuals, thus making a person do guesswork; which can lead to catastrophic failure. Luckily, my dealer's kits come with instructions (both BMW and MB).

I have done full engine teardown etc, again with no experience other than a book and have rebuilt almost every part of a car (less automatic), but I'm also an engineer.

ATLD

Jim:

Thanks again for a wealth of information. We're accumulating alot of posts together. I ask the questions and you answer them. My senior member status is a joke because its a bunch of accumulated questions :)
The bleed screw at the top for the air makes sense. I knew there must be something. On the front axle I swapped out my old bendix calipers and put ate's on both sides. On the rear I only changed one caliper. It is my understanding that the calipers on the rear don't come with alot of options. I thought I might get away with it back there.
The pedal is significantly better than prior to the job. Yet I want that legendary Mercedes feel and don't have it yet.
I don't understand your comment on why one bleeder screw would be in front of a wheel while another is behind the wheel?

Mercedes Man:

Thanks for the comments. I bleed them with the clear plastic hose method in a jar as well. In fact, this might have been Jim Smith's method that was posted some time ago.
Thanks for the idea of flipping the caliper to bleed and then reassembling. Might try that next. Each adjustment so far has brought about a better pedal.

Don

Don,

On some cars, as you look at the position of the caliper in relation to the axle, the caliper on one side of the car will be behind the axle and on the other side of the car it will be in front of the axle. When this is done, the caliper is not required to be "handed" meaning a single design can be used on both sides.

For example, asssume the bleed fitting on the driver's side of your car's rear brake caliper is located on the inside, upper forward section of the caliper, and the caliper is located mostly aft of the axle, so the pads come out to the rear. On some cars the set up will be exactly the opposite on the passenger side, with the caliper mostly forward of the rear axle, and the pads would be removed in the forward direction. In this case the bleed fitting would be on the inside again, but at the upper rear of the caliper.

Once I brought the discussion up, I should have realized your car probably does not have this kind of set up, or you would have already noticed it and never had the problem you now have. Sorry if I wasted a bit of your time with this discussion, but I am almost certain my W123 has the unhanded set up.

One caution if you will be bleeding the last caliper out of position and off the disc - if you don't substitute something for the disc and apply the brakes in this process, it is possible the pistons will come out too far, and you may damage the replacement caliper. I have never tried this, but it may be a reasonable solution.

Good luck Don, hope this task is done soon! Jim

Jim:

That is one last thing to consider. If it can't fit on the disc, I won't try it. I do think I can turn it though. We'll find out one of these days. The brakes are functioning much better as all four calipers are working with new pads in place. But I drove my daughter's car today and the brakes there are simply perfect. Its stunning that an 18 year old car has a better feel than most cars driven off a new lot today.
I'll keep you posted if I have any further luck with this.

Don

Finally
 

I turned the left rear caliper upright (off the rotor), stuck a brake pad between the brake pads in the caliper & bled it with the bleed screw upwards. This yielded some additional air in the lines. I was out of fluid by then so I went down to the local store. On the way there, my pedal was awesome at first but would slowly descend to the floor. I was both excited at the firmness but worried about the gradual loss of pedal. As I came back to the car I noticed a small puddle of brake fluid about 2' in back of the front left tire. Upon getting home, I crawled underneath to find that I indeed had a brake line leak. I believe that this was the culprit all along and only got worse with the additional pressure that came from bleeding and re-bleeding, etc.

How hard are the brake lines to replace? Any idea of expense involved? They look pretty straightforward.

Don

Well, I've been heavily on the road of late and way behind. I was amazed to see such controversy over brake work.

One of the many things I like about the Benz cars is the ease of brake service. Replacing pads on a Benz is probably the easiest brake work you could do on any car. But there is nothing I can think of that is difficult involving MB brakes.

I have rebuilt calipers a number of times with great success. I don't understand the hesitancy to do so. And I certainly can't for the life of me understand how anyone can consider this an unsafe thing to do, if the casting passes inspection of course.

My $0.02,

have to agree with Larry. Pad replacement takes all of 15 minutes, calipers are MADE to be rebuilt. None of that cheap plastic American car crap inside a Benz caliper. I have not had to rebuild any calipers on my 300 but did them a few times on my old 200d. I remember the first time I went into a parts store (way before this place existed) and asked for a caliper for my 200. The guy behind the counter said "You don't replace those, you buy a $7.00 rebuild kit" I couldn't believe that! Had to get a buddy who was into old Mustangs and had every tool ever needed to show me how to rebuild one.

Don,

What failed, the rubber jumper or the steel tubing?

Either is relatively straight forward, and you have some choices if the steel tubing is cracked.

First, if the problem is in the rubber jumper, the replacement is really pretty simple if the mechanical connections come apart cleanly. Sounds like you got the ones off the caliper end, so that should not be a big problem again.

I have done this and just let the line drain down, then replaced the rubber hose and fittings. Unfortunately, getting the fitting where the line connects to the steel tubing might be a chore, and I have broken the steel tubing doing this, mainly because the tubing was not in good shape and could not handle the roughing up it got when I disconnected the hose.

I bought standard steel tubing to replace the stuff in the car (this was an old 1966 or so 250S) and then removed the old stuff and bent the tube to suit. I put it in and it worked fine. The tube and fittings came from a local auto parts place, and the only choice I had to make was how long a length to buy. I am not sure if you buy lines from the dealer or FastLane if you get pre-bent tubing or not. Never tried, but if you do, and you are not handy bending tube, it might be worth it to pay a little more.

Good Luck, Jim