Air in brakes.

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Thu 8 Nov 2001 12:27
Air in brakes. - David W
Just looking at a ZX with "pedal to to the floor syndrome", as bad as I've ever known apart from moving the Land Rover last week forgetting it had no brake shoes or wheel cylinders fitted....we do get so used to a brake pedal with some action under it.

Anyway this is a well maintained car with good brake linings/drums/discs. Calipers fine, as are rear brake cylinders. Fluid was to the top, replaced last year and no leaks anywhere.

Customer says it just went like it one morning.

Eventually found the rear brake lines full of air, bleed through and it's all A1.

So where did that come from all of a sudden?

David
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Thu 8 Nov 2001 12:41
Re: Air in brakes. - Dan J
Hmm - odd one that isn't it? If there are absolutely no leaks anywhere maybe the last time the rear cylinders/brake fluid/other were replaced air was left in the system accidentally and though had no effect where it originally was, has worked it's way to somewhere it has?

I guess time will tell if it happens again but if so surely must be a leak somewhere?
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Thu 8 Nov 2001 13:49
Re: Air in brakes. - Richard Hall
Random stab in the dark - take a look at the compensator valve which adjusts the fluid pressure in the rear brakes (if the car has one). It's probably tucked up above the rear axle where you can't see it. Could be drawing in air through the seals when you brake hard and then release the brake.
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Thu 8 Nov 2001 15:03
Re: Air in brakes. - John Davis
Another stab in the dark. Was the fluid, replaced a year ago, fresh when it went into the system? Even if it was, the hygroscopic properties of brake fluid can allow the tiniest droplets of water to enter the system and these can boil at the caliper cylinders. The resulting compressable vapour can, in some circumstances, allow enough "space" in the hydraulic system to let the brake pedal go to the floor. Has the customer had a recent high speed, heavy braking journey which, if very prolonged, can bring this about ?
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