Unusual Brake problem

Hi

I have a 300tdi Disco, when the brakes are first used they work ok but if I press the pedal staight after, the pedal stiffens up and it takes more effort to brake. If you carry on down the road and then press the brakes they are ok but press the pedal striaght away again, the pedal goes hard again and it takes more effort again.

What I've tried so far

• I have taken the pipe off the vacuum pump and there is suction.
• Tested the servo by pumping the brakes until the pedal was hard and keeping the pressure on while the engine was started and the pedal would only go down very slowly.
• Checked the valve as well by putting a pipe on it and I could only suck and not blow so the valve appears to be working ok.
• Also I have put a pipe from the vacuum pump to servo to by-pass the old pipe but that made no differences.

If anyone has any ideas it would be much appreciated.

Your servo VACUUM PUMP is probably goosed,

BUT


Did you know there is a felt AIR FILTER in the servo?
It is fitted around the pushrod the brake pedal shoves, and if it gets really filthy and choked up it can cause trouble such as you describe. Check it.

However, even though your vacuum pump sucks a bit, I don't think it is sucking nearly briskly enough. It may slowly suck ther pressure down, but that isn't good enough. For the brakes to work properly the vacuum pump MUST be able to suck air out of the servo faster than you can let it in by pumping the brake pedal.

CharlesY

with charles on this one!