110 BRAKE PROBLEM

The brakes were fine on my (somewhat ancient) 110 V8 until 3 days ago when the brake pedal went "soft" and I noticed a lot of fluid leaking from the front right disc brake caliper. I removed the caliper and replaced the seals on the brake pistons and also replaced the brake pads and adjusted the rear drum brakes. In replacing the seals the brake reservoir and pipe leading top the right hand brake caliper emptied. After bleeding the brakes all round (as per manual) the brake pedal was still soft. I bled the front and back calipers and pistons twice more (I've bled brakes dozens of times) but the pedal takes very low, although its operative. I'm convinced there is air trapped in the system somewhere, as the pedal takes much higher when pumped a couple of times. I'm at a loss as to how to rid the system of this trapped air. Any suggestions?

Have you tried a pressure bleeder?

When I stripped all mine down a pressure bleeder was the only way I could get a good pedal.

Also if you have fitted new seals to the pistons it could be that the seal is ‘pulling’ the piston back allowing to much float between pad and disc so that when you brake you h e to first take up the slack, then the pedal gets better.

To sort this on mine after I re-sealed pistons i put the old pads in (very worn) and pumped the pedal a few times till they were in a good position on the discs, then put the new pads back in, I used a lever to retract the pistons only enough to get the pads in - not more - then I clamped the pedal down with a block of wood overnight in an effort to ‘form’ the seals.

Surprisingly it worked....

flat said:

Have you tried a pressure bleeder?

When I stripped all mine down a pressure bleeder was the only way I could get a good pedal.

Also if you have fitted new seals to the pistons it could be that the seal is ‘pulling’ the piston back allowing to much float between pad and disc so that when you brake you h e to first take up the slack, then the pedal gets better.

To sort this on mine after I re-sealed pistons i put the old pads in (very worn) and pumped the pedal a few times till they were in a good position on the discs, then put the new pads back in, I used a lever to retract the pistons only enough to get the pads in - not more - then I clamped the pedal down with a block of wood overnight in an effort to ‘form’ the seals.

Surprisingly it worked....

Click to expand...

That all makes sense, thanks. Just be sure that I haven't missed something, am I correct in assuming that the only bleeding nipples in the system are the ones on the front calipers and rear wheel cylinders?

Yes, unless you've got something quite unusual, that's where the bleed nipples are.

A lot of air can hide in a Land Rover brake system. Sometimes I've found that it helps to let it settle for a while an then bleed again, after it's been allowed to sit while you have a cup of coffee, or even overnight. Just breaking the circuit on a front brake can allow an air bubble into the pipe(s) serving the back brakes and it'll take quite a while to work its way through and come out. I've found a pressure bleeder very useful when working single handed.

About three years ago I replaced the front to rear brake pipe on mine and now find it bleeds much more easily. The only difference I can see is that the original brake pipe had a lot of factory made right angle bends in it whereas mine has smooth curves bent with my fingers. Maybe the sharp bends helped to trap the bubbles.

I'm sure it doesn't apply in this case but some people succeed in getting the calipers upside down or getting the pipe in the nipple hole and vice versa. If the nipple isn't at the top of the arrangement it's going to be near impossible to get the air out as it tends to rise.