Brake fluid leak

[Lotus 50]

I had to fill my brake reservoir a few weeks and about 400 miles ago. The brake pedal went to the floor without slowing the car. I bought som DOT fluid and filled the reservoir. Then I had it towed to a brake shop. They put it on a lift and could find no leaks? So I drove it home. Master cylinder leak? Slow leak elsewhere?

[mbell]

Do you have a brake booster?

If so they are normally the most troublesome part of brakes. Not un known for brake fluid to be sucked into the engine intake from a faulty booster...

[Lotus 50]

Yes there is a brake booster

[alan.barker]

+1 servo

[rgh0]

Most likely be leaks into the booster vacuum chamber but also look for leaks from master cylinder into the footwell being hidden by the carpets.

cheers
Rohan

[Lotus 50]

A woman in a Mercedes tested my brakes an hour ago. I can still lock all 4 wheels. I will look under the carpet.

[mbell]

I'd also pull the brake booster vacuum line and see if there any signs in it fluid.

Glad they still working when you need them. Hopefully you have a very loud horn, horn loudness should be inversely portion to car size...

[Bigbaldybloke]

I had a problem years ago where the brakes almost failed and I had had to top up the reservoir several times prior to that but could find no signs of any leaks. On removing the brake servo about half a pint of brake fluid ran out when I loosened the screws on the vacuum part of the servo. The seals had failed in it and the fluid was leaking from the liquid side to the vacuum side of the servo. It was relatively simple to rebuild with new seals, mine was a Girling one, and from memory I needed to bend a bit of coat hanger wire into a special shape to facilitate the rebuild, but the instructions were in the rebuild seal kit.

[Bigbaldybloke]

Just another comment, the vacuum line normally comes off the top of the servo so until there is a lot of brake fluid in the vacuum side of the servo you are unlikely to find much (if any) getting into the inlet manifold. Certainly there was no trace in my car when the servo failed.

[TeeJay]

I also had the same scary experience, many years ago, of the servo failing, which resulted in pedal to the floor and no brakes.

Pumping the pedal resulted in some brakes. Slow drive home, filled reservoir and seemed ok, but some days later brakes failed again. Car off the road to find the fault.

It was as others have said, brake fluid in the vacuum cylinder.

Mine was a Girling Mark2A, so purchased a repair kit and sorted the problem.
I tried to attach the Girling Manual, but regrettably the file was too large.

So I have selected 4 pages that illustrate the contents, one page which illustrates the dimensions of the compression tool, which is required as it avoids damage to the bores, if used correctly.
I made mine from the wire of a coat hanger.

So if anyone wants the Girling Manual and/or the Instructions that came with the repair kit, then PM me your email address and I will forward the documents.

Girling Vacuum Servo selected pages.pdf

(918.19 KiB) Downloaded 380 times

[Bigbaldybloke]

Just rummaged in my toolbox, bent wire tool still there!