Brake fluid contamination!
 

My brake pedal was near hitting the ground when I bought the car so I thought it only needs a bit of bleeding.

I checked the car at a local mechanic and he showed me the brake fluid. It was contaminated. My rear brakes do not work at all(kinda felt like it) and all brake power is from the front wheels.

Mechanic said replacing the whole system would cost 3000+ however it *might* work if I kept flushing and bleeding the system multiple times, it might work.

Anyone went through this? or anyone went through having the rear brakes not working and it was fixed?

All comments appreciated!

the brake master cylinder seals are the most likely cause .
the X5 has 2 brake circuits , one for the front brakes and one for the rear brakes .
a forum member had this same problem last year and had difficulty finding a mechanic with enough knowledge to find the problem .

the car required a new master cylinder , simple as that .cost a few hundred $ .
you need to have the entire system checked properly . checking all the calipers work properly .
you should not drive the car at all until it is repaired .

If the brake fluid was completely run out the the problem sits on the abs. they wont let you bleed the system out correctly you have to take it to a dealer to get it done. now i was also told that if you unplug the abs default is to open and you may be able to do it.

try flushing the system and see what happens , at least you will know it has fluid .
but if the rear brakes won`t flush , chances are the master cylinder needs replaced , assuming the calipers are not seized .but it should still flush if they are seized .
you can buy a repair kit with new seals for the master cylinder but the bore of the cylinder may be damaged by the contaminated fluid , needs expert examination really .

Could you elaborate on what the indy mech found/recommended? How was the fluid contaminated? If it was water seeping into the brake lines, I would flush it a few times to get all the moisture out. Also, are the rear brakes not working because the fluid is contaminated or because the brake calipers are frozen? If the calipers are frozen, you can rebuild them or buy remanufactured ones to replace...then flush and bleed. What exactly did your indy mean by "replacing the whole system"? Brake lines, rotors, pads, fluid, calipers?

The system does not leak at all. The rear brakes simply do not work. Mech tried to bleed the rear ones and nothing came out. The fronts work perfectly.

Mech also unplugged the brake fluid container and felt the hoses, he felt pressure if you press the brake pedal on both circuits but nothing goes to the rear brakes.

Mech recommended replacing the brake lines, fluid, master cylinder and everything that has rubber in it but he didn't really inspect anything other than bleeding the rear brakes and checking the pressure on the hoses next to the brake fluid container.

Replacing the master cylinder is very reasonable. Any known additive that can be added to the brake fluid then flushed with it that can treat the rubber or open up the rear seal of the master cylinder?

Thanks alot everyone for your input!

What are my chances if I went for buying a repair kit for the master cylinder if only the rear ones do not work and given that the calipers are not frozen?

A repair kit like this one: BMW 5 Series X5 Brake master cylinder repair kit 1586 - eBay (item 270471978790 end time Jun-15-10 08:33:06 PDT)

Sounds like the indy doesn't have the most experience with braking hydraulic systems... or doesn't have all the proper tools to diagnose it. If I'm understanding the problem correctly it most likely needs the master cylinder changed and a full fluid exchange. The replacement master cylinder would need to be bench bleed before installation just like any other car, then I'd simply compress all 4 wheel calipers to back flow fluid into the master cylinder reservoir knocking any small air pockets at the top of the lines out into the reservoir. Then use a pressure bleeder to perform a regular brake fluid flush/exchange to all new fluid. If there are no leaks and no air in the system and the job is done correctly, then the ABS system would not get any air in it and would not need to be activated in the bleed procedure.

You need a dealer or an indy who works with BMW's specifically. Brakes are nothing to be messing around with when you are driving an almost 5,000 lb vehicle.

When a mechanic is telling you $3,000 to maybe fix something its time to run. When you pay that kind of money on a repair all I want to hear is that its fixed.

Does DSC automatically turn also off when ABS is off? my ABS and DSC are also off. I think it might be because Front Linings are out... I changed Rear ones only...