I purchased a 2003 D2 a few months back and I am fixing things slowly. As it started getting cooler I noticed the brake reservior leaking so I purchased a rebuild kit from rovers north and figured I would fix the leak, as I have done before. My Father has been driving the Disco when I am not around because I am gone often. He decided to install the rubber gaskets under the reservior and it stopped the leak but.... Soon after the passanger front brake began to lock up when he was driving it. He said he could loosen the bleeder valve and it would release the pressure and he could drive it again.

I decided to try to figure out the problem when I was home last weekend. I broke the bleeder valve on the front passanger brake and had someone pump it to try to bleed all the fluid. Barely any fluid came out and the pedal felt like it still was building pressure, it wouldn't go all the way to the floor like it should when a brake valve is open. I tried the other three and the same thing, barely any fluid. What fluid that did come out looked to be a mixture of dirty fluid and what appeared to be hydraulic fluid... The thick fluid sat on top of the brake fluid and had a shimmer. All I can think is somone put contaminated brake fluid in the reservoir. Could this mystery fluid be causing pressure to build under heat causing the brake to lock up??

Either way, it didn't seem like the master cylinder was giving any pressure when I was trying to bleed the brakes but the brakes had worked. I took the master cylinder off and put the rest of the rebuild kit in it with new o-rings and seals and then put it back together. While it was apart I pushed on the plunger and it seemed to not have much pressure out but when I released it, it caused sunction and held it until I removed my finger. Making me think it wasn't leaking past. I put everything back together and refilled it with dot4 fluid. I attempted to bleed the brakes once again. Nothing but drips out of the bleeder valves.

Finally, I went to the abs block and pulled the front input line from the master cylinder to see if the abs block was the problem but I didn't have any pressure there either.

My questions after all that was; why did I have brakes before now I don't after trying to bleed the brakes and rebuilding the master cylinder? And what could have caused my front passanger brake to lock up while normal driving prior to the no pressure issue?