Good morning fellow listers,

Right after the dealer replaced all 4 brake discs and pads on my 95 W202 with 57K miles six months ago, the pedal was very firm. Brakes application can be felt with the slightest effort to the pedal. Now after 1.5 K miles, the pedal travel is much longer. It requires more than a third to almost half of the pedal travel for the brakes to apply. When stomping on the pedal, it stops right on the spot, ABS works depending on road condition. But when trying to slow down in city driving, normal braking only start to take effect when pedal is half way down. The dealer rebled the entire system but it still feels the same. They claim that this is normal specially for the W202, and that it takes some time for the pads to properly bed to the discs. But it's be more than 1500 miles since the discs and pads were replaced. I don't think this is normal. Any wisdom and suggestions would be greatly appreciated !

Willy

p.s. brake pedal never sinks to the floor so I doubt it's the MC, but I could be wrong.

Anyone with any ideas ? please help !

Thanks !

what happens with the engine turned off and you pump the brake pedaL, does the pedal firm up.

what happens with the engine running and you pump the pedal?

do you know what method the shop used to bleed the brakes? two man method pumping the brake pedal, or a pressure bleeder?

is the fluid level in the reservoir between the min and max marks?

and is the screen and cap properly fitted on the reservoir?

did the shop use OEM / Mercedes brand pads and discs or aftermarket pads and discs?

Ethan,

With the engine off, the pedal firms up after 2-3 pumps,. Pumping the pedal with the engine running, firms up the pedal just little bit.

The shop uses pressure bleeder to bleed the car.

Fluid level in the reservoir is between the min and max marks and the screen and cap are properly fitted on the reservoir.

The shop (MB dealer) used OEM / Mercedes pads and discs.

It is quite difficult to regulate the brakes when trying to slow down because the braking action is either full force or none.

Willy

Let me give you some information from the Hayne's manual for your car.

It say's for excesive brake pedal travel, three things may be the cause
1) Faulty master cylinder
2) Air in hydraulic system
3) Faulty vacuum servo

This is how you test the Vacuum Servo Unit;
1) Depress the footbrake several times with the engine off, to exhaust the vacuum from the servo. Now start the engine whilst keeping the pedal firmly depressed, There should be a noticeable `give` in the brake pedal as the engine starts and the vacuum builds up.
2) Allow the engine to run for at least two minutes, then switch it off. If the brake pedal is now depressed it should feel normal, but further application should result in the pedal feeling progessively firmer, with the pedal strokes decreasing
on each application.
3) If the servo does not operate as described first inspect the servo unit check valve (I have that operation if you need it)
4) And if the servo unit still fails (after checking the Check Valve) the fault lies within the unit itself. And repairs to the unit are not possible - unit must be renewed.

Ethan,

Thanks for the info ! Did the test and confirms that the brake servo is working fine. BTW, what's the symptom of a glazed brake pads ?

At 82K, our C220 has about an inch of play before the brakes engage, and then it is a very smooth easily modulated feel. It has never been otherwise. It got new rotors and pads about eight months ago and the pedal feel did not change.

It was completely bled about 20K ago with a power bleeder and the pedal feel did not change.

Your dealer is either trying to get rid of you, or incompetent on this matter, IMHO.

__________________
Chuck Taylor
Falls Church VA
'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe

glazed pads? why do you ask?

glazed pads would exhibit either noise and/or poor braking performance. If your using MB brand pads and disc, glazed pads are unlikely. You would have had to use the brakes extremely hard.
MB brakes are very good.

Had you used the archives on this site to research the long pedal travel? I recall a thread on this subject not too long ago, person conplained of spongy brake feel after brake work. (but that may have been on another forum)

I will also add that my mother whom drives a 2002 MB C240, complains of long pedal travel before brakes activate on my 1998 C230. But I will add that a friend of mine who drives a 2002 Honda Accord made a remark of how much better the brakes on my C230 slow the car down at higher speeds.

Chuck : That's exactly the feeling I get, dealer is basically trying to brush me off. What really amazes me is that I am a paying costumer, but they act like I am there for a free ride. Will try to find another dealer or independent.

Ethan : I don't really have any complains at high speed driving as it surprisingly seems to perform better at that speed, besides I keep my distance. What I don't feel comfortable with is stop and go driving here in Rome where everyone is quite aggressive.

Went back to the dealer and was told that the earliest time they can accomodate me is after the new year. What a bunch of a...... !

Willy, If you get a chance test some other C-class cars. My C-230 on which I do all the brake work; pads, disc, pressure bleed. does have a rather long initial travel before pads really bite.
I am not so sure the dealer is cheating you. it may be a difficult system to pressure bleed. Thinking back, the long travel may have occured after the first time I pressure bled. I have bled the brakes twice since and know that the system is filled with fresh fluid which will help the longevity of the unit. I cannot imagine that the three times I pressure bled I left air in the system which causes a spongy feel.

Point I am trying to make is, the dealer may be trying their best. Your initial 1500 miles of a firm pedal then the spongy feel, kind of leads me to believe the cars may be prone to a spongy pedal.

Thanks Ethan, will do that !

I have a W124 E320, but I also have rather long pedal travel before the brakes engage, compared to other cars that I have owned. I asked about it at the dealer and at an independent mechanic. I was told that my brakes were working just as Mercedes had intended them to work. They told me it had something to do with the air assist. Sometimes the pedal is quite high and then other times it is lower. It is also possible to give a little pump to bring the pedal higher. I thought some of this was a symptom of having air in my brake lines, but I was assured that it was normal for the Mercedes brakes.

Although the dealer always replaces my rotors, the independent mechanic is willing to turn the rotors once if it is possible to keep them within specifications. After having the rotors turned, my brakes engaged higher on the pedal and it felt more like other cars that I have owned. I even called and complimented the mechanic and he said that it was because the very precisely machined rotors allowed just a bit better adjustments for the brakes. After a few months, however, the brakes feel like they always did. I think the long pedal travel really is just the way the Mercedes brakes are supposed to work.

The good news is that the brakes are truly incredible at stopping the car from any speed. These brakes bring you to stop with complete control and confidence. No worries here, even if the pedal travel is a bit more than other vehicles. I have absolute confidence in my car’s ability to stop quickly, in spite of the slightly longer brake pedal travel. These cars can really stop!

__________________
I just couldn't give up on my 1995 E320.

I think it might be like always going back to that same bad relationship with an ex girlfriend.
You feel you love them too much, or you are just too stupid to know any better.



Flickr slideshow of my 1995 E320
http://www.flickr.com/photos/24145497@N06/sets/72157616572140057/

[QUOTE]Originally posted by Ethan
[B]

3) If the servo does not operate as described first inspect the servo unit check valve (I have that operation if you need it)

hello Ethan,
My car is a 260E , 1988, and I am interested to know the operation for the inspection of the checkvalve of the servo unit.
Could you provide it?
In advance many thanks

this is from the manual for a 1998 C, I think it will be helpful.

Vacuum servo unit check valve- removal testing and refitting.

REMOVAL:
1) Slacken the unit nut and disconnect the vacuum hose from the servo unit.
2) trace the hose back then disconnect it from the inlet manifold/pump connection (as applicable) and remove the hose and valve assembly from the engine compartment.

TESTING:
3) Examine the vacuum hose, check the valve for signs of damage, and renew if necessary.
4) The valve may be tested by blowing through the hose in both directions; air should flow through the valve in one direction only- when blown through the servo unit end of the hose. Renew the hose assembley if this is not the case.

REFITTING:
5) Ensuring that the hose is correctly routed securely reconnect it to the manifold/pump (as applicable) Connect the hose to the servo unit and tighten the union nut to the specified torque.
6) On completion, start the engine and check the valve to servo unit connection for signs of air leaks. Test the opeation of the braking system exhaustively before bringing the car back into service on the road.

Torque figures for 1998 C-230
Servo unit mounting nuts.....11 lbf ft
Servo unit vacuum hose union nut...22 lbf ft
Vacuum pump mounting bolts.....10 lbf ft

After months of struggle trying to fix the brakes, the brake pedal in my W202 is still very low. It's been in and out of the dealer and still no resolution. Last night I noticed that the brake pedal has a some play from side to side when I try to wiggle it by hand. By the way I have a stick shift and my driving habbit is to switch between the gas and brake pedals without lifting my heel. Anyway I drove to an empty lot last night and did the following test :

- step on the brakes with my left foot; I was really surprised with the response of the brakes; pedal feel was very firm, bite was strong and pedal travel was what it should be
- step on the brake with my right foot and there it was again; soft pedal feel, long pedal travel, and the bite just wasn't there

I will be inspecting the clutch and brake pedal assembly tonight and would appreciate it if somebody can give me some insights as what to look for. Also, is it possible that when the brake pedal is applied from a certain direction, it actuates the MC differrently ? Could this be my problem ?

Would really appreciate all the help that I can get ! This car is becoming a PITA with this problem, not to mention that I have to replace the front windshield because it was hit by a stone two nights ago !

Thanks in advance !
Willy