Bleeding Brakes - no fluid out of both rear brake lines

[robbyb20]

Ok, before i go hijacking chuckwagon976 post about brake booster/servo o-ring any further, i figured id create a new post.

Looking to flush out the brake fluid after a couple years of use and suddenly a notice in less stopping distance while backing up down hill (this happens often in Seattle) and the disappearance of a noticable sqeak on the rear brakes.

Brake fluid in reservoir is a bit dark but still full. I have since removed some of the older fluid from the reservoir and poured in new fluid, never going below the min level. I have used a couple methods to try and get some fluid to come out.

1st go - using hand pump vacuum like this one https://www.harborfreight.com/brake-bleeder-and-vacuum-pump-kit-63391.html
Attach the host to the bleeder (this does not seem snug), open to bleeder and start hand pumping to draw fluid out. I was only ever able to get a dribble of fluid. Closed it back up and tried the rear LH brake, same, but less than a dribble.

2nd go - 2 person method
With the vacuum attached to the rear RH bleeder as well as a bit of pressure on the hose to create a better seal, buddy pumped the brakes and then held down while i opened the bleeder screw and started pumping. I got a bit more fluid out this time, but buddy reported the pedal never released any pressure once the screw was open. Closed it back up and buddy released foot. Did this a couple more times with no success.

3rd go - using a regular brake bleeding kit with a bottle and hose inside the bottle.
Put some brake fluid in bottle to submerge hose, attached to bleeder via the little nipple attachement vs fitting hose over the bleeder, opened and then went to pump. Nothing. Did this on both sides.

4th go - used vacuum directly on brake line
Also tried the vacuum on the brake line itself in teh rear with no results.

So now im looking at what else can be gumming this up. After searching a bit, it looks like this can be caused by a proportioning valve being stuck in a forward position instead of middle. The previous owner gave me a box with some parts, 2 of them being a servo and a pressure reducing valve.

Is the pressure reducing valve the same thing as a proportioning valve? If so, can i just replace and bleed or can i salvage the current one with some work. I am doing this on the street so i dont have readily available access to compressed air (a forum mentioned shooting a quick shot of air in the brake line to try and make it move).

Is there something else I need to be looking at?

Thank you for any insight to help this along.
Rob

 

[Jimmy]

I wasn't following the other thread, so maybe that's where you listed what you're working on. What year?

I've read about actuating the ABS module may help.

Have you worked backwards in the rear braking pipes to figure out where the stoppage is? As you apply pressure to the system, crack the fitting at the next upstream location to see if fluid appears.

Having created a pressure bleeding system out of a garden sprayer (tons of info on the 'net on how to do this) and bought the fitting for the master cylinder, I'm a believer in that setup. So very handy and effective.

Compressed air away from a compressor is achievable with an air tank. I've not tried blowing compressed air into the system to fix something.

 

[robbyb20]

I wasn't following the other thread, so maybe that's where you listed what you're working on. What year?

I've read about actuating the ABS module may help.

Have you worked backwards in the rear braking pipes to figure out where the stoppage is? As you apply pressure to the system, crack the fitting at the next upstream location to see if fluid appears.

Having created a pressure bleeding system out of a garden sprayer (tons of info on the 'net on how to do this) and bought the fitting for the master cylinder, I'm a believer in that setup. So very handy and effective.

Compressed air away from a compressor is achievable with an air tank. I've not tried blowing compressed air into the system to fix something.

whoops, you’re right. 97 D1.

rear brakes won’t bleed. Fronts bleed just fine. Trying to do process of elimination at the moment. So far I’ve filled out: rear calipers/bleed screws being plugged. Trying to figure out if the pressure reducing valve is the same thing as the proportional relief valve. If so, then the valve is stuck i a forward position blocking flow to the rear brakes. My AbS is on the fritz and does not activate like so many other D1s on the road. Sometimes I can get it work if the humidity is right and I tap on the abs sensors in the front wheels.

since the front brakes bleed correctly, I’m hoping it’s not ABS related.

 

[terryjm1]

Have you replaced the rubber hoses? Maybe you have an internally collapsed / blocked hose? If the hoses are old, worst case it is good preventive maintenance. And yes, my understanding is the pressure reducing valve and the prop valve are the same thing. On the ABS, I have been told air gets trapped in the ABS unit and getting it to actuate helps clear it out. I have not had to do that.

 

[robbyb20]

Have you replaced the rubber hoses? Maybe you have an internally collapsed / blocked hose? If the hoses are old, worst case it is good preventive maintenance. And yes, my understanding is the pressure reducing valve and the prop valve are the same thing. On the ABS, I have been told air gets trapped in the ABS unit and getting it to actuate helps clear it out. I have not had to do that.

Have not replaced the rubber hoses, will order those as thats a good idea either way.

While i begrudginly dont want to work on the ABS, you all are right and i have to rule that out and get it working. I have 2 new ABS sensors, ill do the blink test to see whats tripping it and hopefully it can be fixed with 1 or 2 new abs sensors.

Thank you for confirming that the pressure reducing valve and prop valve are probably the same thing. That helps with the process. I also see in the box of items the previous owner gave me included an old used pressure reducing valve and a servo. Im wondering if they had the same issues, sorted it and now its back. I have had to replace a few of the parts they worked on the past 3 years.

 

[robbyb20]

ABS blink test results in 2-3. The blink test documentation says the fuse is 35a, the diagram on the engine fuse box says 40 and 30 (which is what i have). Should i swap the 30a out with a 35a? Also ordering a new relay just in case too.

 

[terryjm1]

Would you mind detailing the blink test procedure? My ABS light has been on since I replaced the starter (bumped the ABS sensor wire).

This D1 is a TDi conversion and I no longer have an engine ECU. I know the ABS has its own ECU but I am wondering if the main ECU is needed to do this. The ABS worked fine after I did the conversion and had removed the ECU.

 

[robbyb20]

Would you mind detailing the blink test procedure? My ABS light has been on since I replaced the starter (bumped the ABS sensor wire).

This D1 is a TDi conversion and I no longer have an engine ECU. I know the ABS has its own ECU but I am wondering if the main ECU is needed to do this. The ABS worked fine after I did the conversion and had removed the ECU

You can try this document. One thing it doesnt detail is which is Pin 5 and Pin 15 on the obd port. If youre looking at it from the front, with the wider part on the bottom, on the top row, its the second pin from the left and on the bottom row (wider section), 4th pin from the left. Do not put it in the 16th pin, this will give you a bit of shock.
http://ABS Blink Codes
https://drive.google.com/file/d/0Byt3ogVBq68RZ2pYcVVERk0yeWM/view?usp=sharing&resourcekey=0-jAyvYpVxjD74cTOI5nybCA


Also, mine is fixed. I was coming down a hill and felt the pedal give way and move much further. I was able to pull over and finally able to bleed to rear brakes. Im pretty sure this was due to to prop valve being stuck and then becoming unstuck due to gravity. Full braking power has returned.

 

[discostew]

I would try bleeding out the front wheels with very gentle pressure on the pedal. Thats how you re center a proportioning valve.

 

[robbyb20]

I would try bleeding out the front wheels with very gentle pressure on the pedal. Thats how you re center a proportioning valve.

Thank you, I think this is what ultimately what helped move it back to center. I bled the fronts slowly, had to take a quick drive and about 10 min into the drive the brakes became very soft. Pulled over and bled the rears and its back to normal.

Is this pretty common to happen or do i need to look at replacing the proportioning valve in the near future?

 

[discostew]

No that’s normal operation of the valve. If you have a major fluid leak in the system the valve gets shifted to that side and limits the fluid flow out that line. So that’s why gently bleeding out the other side brings it back to center. That’s pretty much any vehicle.

 

[WaltNYC]

Would you mind detailing the blink test procedure? My ABS light has been on since I replaced the starter (bumped the ABS sensor wire).

This D1 is a TDi conversion and I no longer have an engine ECU. I know the ABS has its own ECU but I am wondering if the main ECU is needed to do this. The ABS worked fine after I did the conversion and had removed the ECU.

Discovery I - ABS Blink Code Procedure

RSW Solutions - Land Rover vehicle diagnostic tools

www.rswsolutions.com

 

[robbyb20]

I would try bleeding out the front wheels with very gentle pressure on the pedal. Thats how you re center a proportioning valve.

Welp, they left just as fast as they came back, the rears aren't working again. I am not losing any fluid from the reservoir so not sure there's an actual leak somewhere or if I just never actually got the valve back to middle this past weekend.

I have new brake lines ill put in as well since the old ones are original and try slowly bleeding the fronts again. If that fails., i also have a new proportioning valve on hand.

 

[ERover82]

I think the valves get corrosion in them since brake fluid is hygroscopic and rarely gets changed often enough. I remember having this issue on a D1 and eventually figured out no fluid was coming out one pipe at all. I got pissed and stomped on the brake pedal and it blew a geyser of muddy fluid out.

 

[roverover]

Sounds like a master cylinder the front and back are separate circuits

 

[discostew]

Sounds like a master cylinder the front and back are separate circuits

Yeah or just a bunch of air that went back up into the master cylinder. You’ll never push air down those brake lines from the master. Have someone put light pressure on the pedal and crack those lines loose at the master. Then the lines at the modulator.

 

[robbyb20]

Thanks for the help guys. Im going to wrangle someone into helping this weekend and see what we can accomplish.

If im going to replace the flexible brake lines anyway, should i do that before or after attempting to bleed to master cylinder?

 

[boxster]

Change the hoses first, you might have a hose that’s collapsed inside and not letting the fluid to flow.

 

[discostew]

I agree with Boxter. Replace everything your going to replace. Then bleed it out. These things are a bitch to get bled sometimes with those valve getting shifted like they do. I would avoid trying to replace it unless your sure it needs it and then I would just plan on the brake lines getting replaced with them.

 

[robbyb20]

Brake lines replaced. Tried bleeding the fronts slowly again to see if if something would budge, still nothing out the rears fronts bled fine and the pedal is pretty stiff. Waiting for a buddy to help and try with the master cylinder.

if that doesn’t help, I have a new prop valve on hand.

anyone know what the unused valve on it is used for?