I have a 1998 Discovery and I just replaced the master cylinder. I bleed the brakes serval times. I have driven it three times since and each time I go a few miles ( more each time) and the brakes lock up. I end up having to open the bleeder valve on each wheel to get them loose. Each time I have done this I am able to go farther before it happens again. Any ideas?

 

Describe the process exactly as you did it when you bench bled the master cyinder and bled the brakes.

 

I bench bled the master cylinder according to the included instructions. I put it in a vice and made sure the fluid container was level. I connected the incuded hoses and placed the end inside the opening in the fluid. I topped off the fluid. I then slowly pushed in the plunger 3/4 to 1" and released. I waited in-between strokes (painfully slow). I did this for about 30 minutes until it appeared to be clear of air. After installing the master cylinder I began to bleed the brakes. I went in order PR, DR, PF, DF. I connected a tight fitting hose to the bleed valve and put the end into a container with fluid so the hose was in the fluid. I had my son pump the brakes three to five times and hold the petal while I opened the bleed valve. He kept his foot on the petal with pressure until I tightened the bled screw. we did this several times until I did not see any air in the lines. I went around the vehicle three times.
I now have a new problem that I think is the real issue. After bleeding the brakes several times and going for a ride I discovered that its only the passenger side rear that is locking up. Once I open the bleed screw on this wheel only the vehicle is fine. this has happened several times ( bled the brakes, gone for a drive, the passenger rear locks up, i relieve the pressure through the screw and Im off and going again for a few miles). I do make several stops along the way to test the brakes, a little more than normal driving but this should not be an issue. Any help is greatly accepted as the nearest Land Rover dealership is 2 hours away and I want to do this myself! I have many years of experiance with Chevrolet (complete restorations) and I am baffled with this issue.

 

Sounds like you still have air in the system, air lock. As the system heats up from consistant breaking, it would build pressure in the forcing the fluid to lock in the caliper.

You might want to consider investing in a brake bleeding tool that forces the fluid though the system, without pumping the brakes.

 

How does the brake hose for the Pax rear look? Might be internally damaged and not letting the fluid leave the caliper. Even air in the system should let the caliper disengage when you get off the brake pedal. Could also be a bad caliper. I would start by inspecting the brake line that is specifically for that particular caliper since you don't have that problem with the other calipers.

 

When problem start , loosen nuts between master cylinder and servo.

Check gap between master cylinder and servo

Regard

 

same exact problem Im having currently except its my front calipers, Ive been working on this for a month now. Ive replaced the front calipers, hoses, MC, proportioning valve, and ABS, and nothing has helped me solve the problem

 

Gotta use the factory master cylinder.

 

Mmmmmm so has anyone got some REAL advice for brake issues ?

Before I give up totally

OZ

 

Well, my brakes have not failed, but they have never felt terribly firm. So, I replaced all the rubber lines with stainless steel and put speed bleeders on it. I also got Akebono pads all round.