Sl W129 Brake problems

vikingo34

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I have a Sl Class w129 but since 2 year ago i began to have problems with the brakes and sometimes i try to push the brake pedal all the way but it was difficult to stop the car so i send it to a mercedes dealer but the mechanic can't fix the problem with the car and they damage the brake discs and the pads, so i decided recently to try with another mechanic and i have to buy new discs and pads, I buy ventilated discs for the 4 wheels and Ceramic pads (Akebono) but this didn't fix the problem, I have another mercedes S600 i did the same buying new discs and pads and this car stop like hell, but my SL Still have the same problems it needs a long distance to stop and you have to push all the pedal to stop the car, and the pedal feels too soft not like the other that stops only with a touch of the pedal. Do i have problems with other part of the brake system?
 

Dave Brooker

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I have a Sl Class w129 but since 2 year ago i began to have problems with the brakes and sometimes i try to push the brake pedal all the way but it was difficult to stop the car so i send it to a mercedes dealer but the mechanic can't fix the problem with the car and they damage the brake discs and the pads, so i decided recently to try with another mechanic and i have to buy new discs and pads, I buy ventilated discs for the 4 wheels and Ceramic pads (Akebono) but this didn't fix the problem, I have another mercedes S600 i did the same buying new discs and pads and this car stop like hell, but my SL Still have the same problems it needs a long distance to stop and you have to push all the pedal to stop the car, and the pedal feels too soft not like the other that stops only with a touch of the pedal. Do i have problems with other part of the brake system?

Has the brake fluid ever been changed?
 

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To check the servo,,put your foot hard on the brake, then start the engine, if the pedal sinks further then the servo is working. It the brake pedal has a lot of travel the change the master cylinder.
 

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Leaking slave/master cylinder/calipers? ABS controller? Bias valve? BAS if fitted? Brake hose damaged and expanding? Could be any number of things though shouldn't be hard to fix?
 

kth286

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You could put it through an MOT via a Mercedes dealer (very cheap) and if when it fails, they should then tell you what the problem is.

Where you located perhaps we can recommend a good Merc dealer such as the Tony Parslows in Basingstoke (do their own MOTs)
 

television

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Have you tried what I said in post 3 to see if the servo is working
 
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vikingo34

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Leaking slave/master cylinder/calipers? ABS controller? Bias valve? BAS if fitted? Brake hose damaged and expanding? Could be any number of things though shouldn't be hard to fix?

We already do that, the brake hose is not damage
 

television

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Have you put your foot on the brake pedal and pushed hard keep it pushed hard and start the car,,does the pedal go down further once the engine starts
 
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vikingo34

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Have you tried what I said in post 2 to see if the servo is working

thanks a lot, if the pedal when i start the engine go further all the way when it stops it's the servo? if that's the idea i already do that and the brake goes all the way
 

television

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Its not easy to explain.

With the engine off,,does the pedal go very far down ?

keep the pedal down with your foot and start the engine, does the pedal now go further down.

You have two independent brake circuits. and the front and rear brakes have their own parts in the master cylinder, number 25 in the link
http://www.detali.ru/cat/oem_mb2.as...GA=722.353&CT=F&cat=515&SID=42&SGR=060&SGN=04


You have a brake booster that give the extra power when the engine is running,


If 1 of the rubber pistons fails the brake pedal will feel very soft and go down a long way. number 101 is the pipe from the engine that operates the booster
http://www.detali.ru/cat/oem_mb2.as...GA=722.353&CT=F&cat=515&SID=42&SGR=060&SGN=04
 

television

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thanks a lot, if the pedal when i start the engine go further all the way when it stops it's the servo? if that's the idea i already do that and the brake goes all the way

What can happen is that when you put in new brake fluid, if the peddle is pushed too far when bleeding the air out, it can damage one of the seals in the master cylinder
 
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vikingo34

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Today i already try that when i engine is off the pedal go very far down maybe all the way down the first time then when i start my engine it gets softer and goes the rest of the way down.
 

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The you need a new master cylinder, and that will solve the problem,,the servo is working.

To fit the new cylinder the system will have to be re bled to get any air out and your car will be fine:D:D
 
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vikingo34

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still have the same problem

after a long time with my mechanic we install a new booster and a master cilinder in the brake system but the problem still persist does anybody know what other part of the brake system is making me this problem, thanks a lot.
 

television

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Is the servo charging up,, run the engine and stop it. then push the brake pedal and it should get harder and harder to push as the pedal rises, turn on again and the pedal should sink further down.

If it is not then perhaps the one way valve in the pipe from the servo to the inlet manifold
 
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vikingo34

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i will try today , and i will let you know what happens, and thanks again.
 
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vikingo34

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the problem persist the servo is ok the only thing left is the abs any idea?
 

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Is the brake system losing fluid over time? Has the car been in an accident?

Have the brakes ever worked perfectly on this car? If they have, what happened to the car (service, accident, etc) between them working OK and the pedal going soft?

What is the chassis number?

Nick Froome
www.w124.co.uk
 
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vikingo34

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thanks.
The car is not loosing fluid, the car has never been in an accident, we buy this car new from the dealer today it has 40,000 miles, about 6 years this car began to have problems with the brakes and the mechanics of the dealer told me that the problem was the brake disc we buy new discs and new brake pads but the car still have the same problem in june of 2010 i buy the booster and the master cilinder or brake for the car and still have the problem we try the servo and is ok, and the pedal is going soft very soft
 


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