Brake pressure

[Jonny XKE]

Having a continual problem with the brakes. The brake pedal initially works as you would expect with pressure in the pedal and then after a drive it suddenly loses all pressure. The brakes still work if you press the brake down right to the end of travel. If you pump the pedal it comes back initially then happens again. On the way back after driving for 5 minutes they started working again normally for the entire drive home. The servo and master cylinders are new. Any ideas?

[christopher storey]

You have air in the system somewhere . The E system is not all that easy to bleed successfully, so a re-bleed, making sure that 2 of you do it with the pedal operator holding the pedal down at the end of each stroke while the bleed screw operator closes the screw completely before the pedal is released, may effect an improvement

[Jonny XKE]

Thanks Christopher ... I hope it is that simple. Do you think a good local garage can cope with that or should I drive the 25 miles to the "specialist" who did the brakes in the first place.

[christopher storey]

Johnny : I wouldn't bother with the specialist if they have made a mess of it first time . I should ask your local place to do it, but emphasise that either my method as described above , or a vacuum method should be used. Details of the latter have been discussed on this forum many times . One of the problems which often arises is that because the rear bleed screws are difficult to get to , ( unless remote bleeders have been fitted ) people are lazy about the method used , and if the screws are not done up before the pedal is released each time, air can be sucked in between screw and caliper casting

[Joes66]

It could also be a faulty master cylinder,servo cylinder
Or even a leak somewhere
Is the brake fluid level going down?

[Jonny XKE]

The brake fluid hasn't gone down.

Its beyond me and I have limited time. I think it best to send back to the garage who did the work in the first place. I'll let you know how I get on and thank you for all your suggestions which I have "helpfully" given to the garage!