Series 1 4.2 Brakes

[AussieEtype]

I have been helping a friend with his rebuild of his Series 1 4.2 Coupe. His brake system has been completely replaced with new parts. ie New master cylinder, new booster/master cylinder, new metal pipes, new rubber pipes, four new calipers - all new not reconditioned.

The car was "MOTed" last week and driving around showed up a couple of minor issues that show up after a car has been off the road for a long time. Brakes were initially OK but have a problem that is hard to diagnose. When applied the brake pedal slowly goes down to the floor after initial pressure has been felt - pumping them does not improve this so unlikely to be air in the system - however to be on the safe side brakes have been checked for air and all clear. There are no fluid leaks in the system.

We suspect that a seal in one of the master cylinders is allowing fluid past it causing the system to slowly loose pressure as pressure is kept on the brake pedal. The brakes work fine but when stopped with your foot on the brakes the brake pedal slowly goes to the floor.

Any ideas would be appreciated.

Thanks

Garry

[tinworm]

I would watch the fluid level in the reservoir while pressure is applied to the pedal - if it rises there is your answer.

[AussieEtype]

Thanks - but no visible change or movement.