Sinking puma brake pedal.

[wally]

The brake pedal on my 2012 130 is misbehaving and I wondered whether some clever chap out there might be able to help diagnose the problem. With moderate to hard braking all is well if pressure is kept on the pedal. But if one then reduces pressure on the pedal (but still holds some pressure) such as you might when stopped at traffic lights the pedal will slowly sink all the way to the floor. If you then pump the pedal pressure is restored. It doesn't appear to be losing any fluid. This problem appeared immediately after having had a brake fluid flush at the dealer. It was sent back to them, but they've failed to rectify it. What do folks think?

[Rok_Dr]

I'm betting there is still some air in the system, so get it bleed again.

I'm having the same problem with the GTV6, a rear hose started leaking earlier in the year, which triggered a protracted rebuild including a new master cylinder. Got it back last week and still not 100%. Mechanics advice was it needs another pressure bleed as the system is notorious for air traps.

Separately I was chatting to a bmw mechanic last week who bought my sons E21 and he said the record for him was 4 bleeds to get air out of the lines.

Cheers

Steve

[strangy]

Sinking to the floor without losing fluid ( at least noticeably) is usually a master cylinder issue with fluid passing through and around the cylinder circuit.
Often new fluid which has replaced particularly old or contaminated fluid will highlight tired seals or loosen sludge etc bring this problem to light.

Did you or workshop do the fluid change?
I don't disagree with bleeding the brakes again, however, a pedal sinking to the floor because of air must have had a crook bleed job.

[Rok_Dr]

Agreed if a bleed doesn't work then the master cylinder would be the next thing to look at.

Cheers

Steve

[Avion8]

The brake pedal on my 2012 130 is misbehaving and I wondered whether some clever chap out there might be able to help diagnose the problem. With moderate to hard braking all is well if pressure is kept on the pedal. But if one then reduces pressure on the pedal (but still holds some pressure) such as you might when stopped at traffic lights the pedal will slowly sink all the way to the floor. If you then pump the pedal pressure is restored. It doesn't appear to be losing any fluid. This problem appeared immediately after having had a brake fluid flush at the dealer. It was sent back to them, but they've failed to rectify it. What do folks think?

I had exactly the same problem on my old RRC. It was using a tiny amount of brake fluid & eventually I traced the problem to a pin hole leak in the rear rubber hose. It didn't even leak on to the ground, although there were traces on top of the diff housing. Replaced the hose & all is well now.

[wally]

I just had a local mechanic bleed them again and it's still the same. Maybe it's time to look at the master cylinder. It's a bit early in it's life for problems, but funny things happen I suppose.