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Discussion Starter #1
My 1999 C 220 CDI has covered 157k miles. Arriving at work a week ago the brake pedal was rock-hard - no perceivable braking effect and I went flying accross a roundabout at the end of a dual carriageway. Luckily no-one was coming and some furious down-changing shed enough speed to get around the roundabout.

In the car park, if I pressed very, very hard on the pedal, there was just about enough braking to gently stop the car from walking speed.

Trying the car at lunch time, the brakes were fine. ABS working in forward and reverse. I called the RAC out who suggested it may be the master cylinder and recovered the car for me.

It has since been to my local garage and an independent MB specialist. Neither can find anything wrong, the computer didn't log anything (even though at the time it put the ABS warning lamp on). The MB Specialist says the Server Vacuum pipe was kinked and worn, so they have replaced that, but can give no assurance they've fixed the problem. I'm not convinced.

Anyone had a similar problem? Any idea what to try? I may take it to yet another garage and I may get them to change the master cylinder as suggested by the RAC. Help!!!
8O
 

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whens the last time u flushed your brake system?? supposed to be every two years or so. maybe the booster is on its way out?, just some ideas..
 

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Hi. I've not bled the brake system (had the car 2 years), so that may well need doing. However, when you say 'booster' I assume you mean the Vacuum assist from the Servo. Loss of Vacuum to the Servo is definatley not the problem.

I took the car onto a straight, quiet road and at speed killed the engine. I then used the brakes gently several times until the pedal became 'hard' as the Servo ceased to be assisting the brakes. With some effort, I then managed an emergency stop from about 30 mph - managing to lock one front wheel.

The problem I experienced was total failure of the brakes to apply. May as well have had a brick behind the pedal, it simply would not move at all. The car continued like this for several braking attempts as I limped into the car park. Starting the car a couple of hours later it was working fine and has continued to work fine since. It's been to 4 garages now, covered 80 miles or so of mechanics trying to reproduce the problem. It refuses to do anything other than work perfectly. :!:

I suspect an electrical problem that was 'reset' when the engine was turned off. I don't see a physical failure consistenly not working for several consecutive uses of the pedal, then a couple of hours later consistently working fine. I pray I'm wrong as I'm sure ABS computers don't come cheap... :cry:
 
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