Glyn M Ruck

A South African owner has contacted me regarding a brake pedal that sinks to the floor under constant light pressure. This is on a C220 CDi. We know of at least one other car that does this, namely a new gasoline powered Blue Efficiency. The fact that this occurs with a gasoline unit would seem to negate the diesel vacuum pump. The car in question suffered this after a front pad change. Benz has been unable to correct. Possible causes raised have been - front callipers (replaced), master cylinder (replaced), the ABS unit (original)

Please see below including video clips etc. We would appreciate members inform us if they have experienced a similar problem & any thoughts on a solution. MBSA have washed their hands of this issue.

The saga:

Quote"

Mercedes-Benz Nightmare

Updated 30 March 2011
The following is a true story and I am prepared to swear to that through a Notary Public if required. The vehicle is a Mercedes-Benz C220CDI – WDD2040082R007238 manufactured in South Africa. Please note that “Mercedes-Benz South Africa” from here on is referred to as MBSA. The vehicle is on an ASSYST PLUS service plan (full extended warranty) and may therefore only be worked on by an approved Daimler AG dealership or MBSA themselves, in spite of their apparent inability to understand the cause of or to repair the problem.

Brake problem. (The short story)

Below is a link to download a short “un-edited” movie clip (17 Mb) that demonstrates the brake pedal going to the floor. For the first 35 seconds, I allowed the car to warm-up, so please be patient. You may use a stop watch to time exactly how long the pedal takes to reach the floor (or the mechanical limit of the brake pedal movement – a distinctive “cluck cluck” noise can be heard as the pedal bottoms if you turn up the audio).

http://radue*********/MercedesBrakeProblem/110228.wmv

Now imagine going down a steep hill or entering an underground car park and having the brake pedal slowly disappearing as demonstrated in the above clip. This actually happened a few days after the meeting I refer to below and was reported to MBSA.

28 January 2011:
I attended a meeting at MBSA Centurion headquarters where they recorded minutes. I quote from the minutes of the meeting under heading - Technical Concerns:

“Braking issue where the brake pedal goes all the way done to the floor board
and it seems that the brakes does not have pressure.” sic

As of this date MBSA are officially aware of the braking problem. Several attempts were made to fix the brake problem apparently in communication with Daimler AG, but I have no proof of this, only hearsay. I did ask for copies of this communication but my request was ignored.

1 March 2011:
On instructions from MBSA, the car was taken to Cargo Motors Bedfordview where MBSA would supervise the repair of the brakes. More parts were changed and “tests” conducted – I am not able to attest to this.
During this period I did research on what the law in South Africa is regarding brakes. I discovered that the South African Bureau of Standards had a document “SANS 10047:2009” which is the South African National Standard for “The testing of motor vehicles for roadworthiness”. The reference to this document was published in the Government Gazette number 32981 dated 5 March 2010 on page 44. I informed MBSA of this document and they obtained a copy thereof. Page 29 of this document clearly deals with my brake problem. I quote:

"5.35 Service brake operation (inspection in vehicle)
Reject if
…..
b) in the case of a hydraulic system, there is sponginess or the pedal creeps down
when a light, firm pressure is maintained on the pedal, or
….."

In other words, no matter what else is correct in the test, the vehicle is not road worthy (by virtue of the clause “Reject if”) – that is the Law!

25 March 2011:
In spite of MBSA being aware of the law as outlined above, they sent me an email and I quote from it:



Please note that the independent brake test referred to above was simply having them press the brake pedal hard while the car on the test rollers. They failed to report the pedal creeping problem. This document may be viewed here:

http://radue*********/MercedesBrakeProblem/Mar08s.jpg

28 March 2011:
I collected our car at Cargo Motors Bedfordview where MBSA were “repairing” it and could not believe that they had not fixed the brake problem after FOUR WEEKS! I drove the car directly to a roadworthy test station in Edenvale and asked them to do a full test. As expected, the inspector failed the car because of the brake pedal going down to the floor, and therefore is not in compliance with the law as defined in “SANS 10047:2009”.

http://radue*********/MercedesBrakePr...rthyTest-s.jpg

Please can someone help me get MBSA to fix or replace this vehicle. The car is in my garage and may not be driven on a public road as it is not roadworthy.
Keith Radue
Email: keith@radue.co.za

Sportstick

I notice only the "hard parts" have been addressed in your intro...calipers, pads, etc. I also assume the system has been fully purged and reloaded, so that he's not compressing air, and that the fluid level has been maintained and leaks have been ruled out.

I wonder if somewhere in a line there is a defect similar to an aneurysm? Could there be some weakened part of the line which appears normal when not under pressure, but starts to expand and give when the pedal is applied? Have the lines been replaced?

Glyn M Ruck

Brakes have been pressure bled to WIS method - no known air - no balooning flexible hoses (they tried that excuse) - no leaks.

Interestingly - Benz flew out new front callipers from Germany even though they have a plant here, but to no avail.

EDIT - after doing all that they sent the letter now posted above in the original document.

Glyn M Ruck

We have posted this to the UK Benz forum as well to capture the largest possible audience for input.

http://forums.mercedesclub.org.uk/sh...499#post691499

lingnoi

On the German forum motor-talk there is a thread about "sudden brake failure". If you need further infos about this thread feel free to pm me.

Regards, L

jinsu

Which year model is this?
Did the brake loose from all four wheels?
I haven't got the same problem on my 2011 C200 CGI BE.

tanktube67

The only two things that it comes to mine that will make the pedal sink to the floor without any visually leaks are

1) Defective master cylinder (already replaced)
2) A defective ABS unit

Glyn M Ruck

Hi Tank - Can you work out where in the ABS block we could be bleeding off pressure We will look into any feasible suggestion. Benz can't diagnose.

tanktube67

The brakes were already pressure bled (best way to bled) so should be no air in to the system my lucky guess is that the ABS unit has an internal leak.

Glyn M Ruck

mleskovar

Carsy

Can a brake specialist isolate the ABS ESP system by capping the lines ?

It should not be too difficult or take much time.

This should answer the question on whether the ABS ESP is at fault.

mike210

I dont understand how brake calipers cause a brake pedal to fade,
what you describe usually sounds like an internal leak in the master cylinder.
the correct Mercedes test for your complaint is a high and low pressure brake test.
It is performed by connecting a pressure gauge to the left front caliper and the vehicle is started and brake pressure is applied then a brake pedal jack is used to hold the pedal there after 5 min the pressure must not drop more than 5 percent. the low pressure test you switch the engine off and pump the pedal to release all booster vacuum then press the pedal down and insert jack and adjust to a pressure of 3 bar during a 2 min period the pressure must not drop. if that test passes your brakes are normal

Glyn M Ruck

Calliper over return can cause a low pedal that immediately comes up with one pump. This is not typical of calliper over return.

Glyn M Ruck

Has anybody here tried to do this with their own W204?

Glyn M Ruck

John - Keith has a German car specialist that is prepared to have go at this issue. Problem is that in terms of SA warranty - MBSA will void the warranty.

Unfortunately not like Australia where you can have a car serviced by a third party & keep your warranty intact. Here the OEM would void the warranty.

He can't drive the car because his insurance won't cover an unroadworthy car. Between a rock & a hard place.

Carsy

May be time to go to the local press with the issue. In for a penny in for a pound.

Letting it be known publically & embarrassing them with logic & common sense may bring a response.

Glyn M Ruck

Yes - it's going to the press, the AA, the SABS etc. We have to force Benz into action. One of the reasons for posting is to investigate if others have the problem. Seems some cars in Germany have the issue thusfar.

keithrad

Thank you Glyn for the excellent work you have done in presenting my problem, I really do appreciate it.

I have sent a pm to lingnoi to ask him to crosspost this thread to the German forum. I am sure that our car could have been involved in a similar incident.

jinsu our car is a 2007 C220 CDI. How many wheels "let loose" I don't know, but my better half was proceeding carefully (as the ramp was wet) into an underground parking in the middle of Johannesburg and was almost at the second level when the car "lurched" forward for several metres. Lucky for her there was nothing in her path and she kept control of the vehicle in spite of the brake pedal being down on the floorboards. A quick pump and the brakes were back.

The loan car from m/b was a 2011 C200 CGI Avantgarde below is a link to a movie clip I took just before returning the car.
http://radue*********/MercedesBrakeProblem/mb200cgi.wmv

jinsu

Hi Keith,
I'm also in Joburg. It sounds like some one way valve losing fuction after a few minutes.
I'm driving a manual C200. I do many incline stop and start everyday. I can imagine the problem will cause accident.
I've tried mine yesterday. It ain't happen yet.
I will support you if MBSA does not action to its customers.

Glyn M Ruck

The fact that Benz started replacing things on the car tells me that they know it is not right. They could not resolve the issue which resulted in another BS letter below! As we said above we know of one other brand new vehicle that is doing this. Thusfar I'm pleased that other forum members do not seem to be suffering this issue with their vehicles. We know of issues in the UK & Germany - let's see what the next few days turns up.

AkaSigFreak

Wow! Sorry to hear about your problems. I don't know if this would be a similar situation: When the GLK was first coming out, I was invited by my dealership to come test drive one. As soon as we left the dealership, I approached a stop light and when I pressed on the brake pedal it went to the floor board. I immediately told the sales manager that something was wrong with the brakes. He had me return the vehicle and his service manager took it in the back. Never heard anything else about it.

tanktube67

Sorry to hear that it’s coming to this, the big fish always want to eat the little fish.



Carsy, has a good suggestion, all you guys need is a couple of union blocks and a couple hose lines to connect the blocks.

Glyn M Ruck

Here is the ABS schematic & three operational modes from Benz own training programme. Without an external leak I still don't understand where the fluid could go to give you a low pedal without a leak being visible unless the line dampers (11) can accommodate sufficient fluid.

Carsy

Glyn,

Thanks for the interesting line diagrams.

I reckon that the problem has something to do with the pressure reducing solenoids Y7, Y9 ,Y11 & y 13.

If one of these were passing due to a faulty v/v or seat or retaining spring or being told to open through an electrical fault when the gentle pedal pressure was applied there may not be enough hydraulic fluid available to prevent the pedal reaching the floor. The accumulators or line dampers may take too much & cause the problem.

What is the receiver 10 ?

Interested to hear other views.

JC