I recently had someone replace the pads, rotors, calipers, and lines in the rear on my 1998 Land Rover Discovery. At first, they only did the section of lines from the axle to the caliper when they did the calipers/rotors/pads, and since then, you basically have to press the brake pedal to the floor to get the brakes to engage. I then had the lines leak further up, so he replaced the rear brake lines almost all the way up to where they connect to the little box where all the lines go in. When I bleed the fronts, the pedal goes all the way to the floor and a steady stream goes out. However, when I bleed the rears, the pedal doesn't move much at all, and the brake fluid kind of just trickles out, and the pedal never firms up anymore after numerous bleeds. Could the guy who replaced the lines have accidentally removed the proportioning valve or some sort of pressure valve that keeps the rear brake lines pressurized? Any help is appreciated

 

The proportioning valve should be on the inside of the drivers side wheel well. I doubt they would have removed it. But who knows.

I have seen this happen to a couple of trucks. Total loss of rear brakes. They were not my trucks so I'm not sure if it's the proportioning valve that went bad or the ABS modulator. But I'm pretty sure it was one or the other on those trucks.

 

Well he replaced the lines almost all the way up to I believe it's the ABS modulator (a silver box that all the lines go to). Is the proportioning valve located within the lines or is it up by the brake booster/master cylinder/reservoir?

 

It's mixed in the lines. Both rear lines come out of the modulator. You could always try bleeding the lines at the modulator and see if at least you have pressure getting to the lines. Then you'll at least have an idea of if the issue is with the new lines or something before them.

Here is an image of the brake lines.

 

So is the proportioning valves the little cylinders right after the brake lines come together along the driver side? And how do you bleed the lines at the modulator?

 

It's #17 and should be bolted to the engine side of the drivers side inner fender. If you look down below the master cylinder you should see it.

As for bleeding the lines, it's the same as anything else. Have someone press the brake pedal and then crack open the brake line on the modulator. If fluid come out and the pedal drops you've got pressure at the front of your lines. If not something is bad. Just work your way back until you find where it is.

 

Oh yeah, don't forget to tighten the line again before your helper lets up on the pedal.

 

Okay thanks! I don't think he would have done anything with the proportioning valve then he only replaced the lines. I also might need to look into replacing the rear flex hoses where the two lines leave the axle, I don't believe he replaced them, and I've heard that if your lines are old the sometimes expand during use and therefore don't build up pressure.

 

Is your buddy a mechanic or at least familiar with bleeding techniques? You can always remove the ABS modulator and plumb your brakes without it. Your ABS probably doesn't work anyway.

 

Yes he's a very experienced mechanic. I didn't even think the thing had ABS, I get no light when the key is on and I haven't ever noticed it engaging. Wouldn't removing it cause issues or would it just turn it into a regular braking system?