How to Reset Brake Proportioning Valve after fluid is cuttoff?

[oversite]

Hi all,

My disco 1 ran out of brake fluid becasue the master cylinder was leaking, my understanding is that this has led to the proportioning valve to cutoff the fluid flow to the rear.

I have now fixed the master clyinder and the rear brakes are not getting any fluid?

so my question is how to I reset the brake proportioning valve? My mechanic thinks we will have to replace the unit but Im trying to save some $$.

Thanks for any advice.

[Discomark]

No Idea but heres a pic of whats inside one, maybe worth pulling it apart to give it a clean before getting a new one.
http://img19.imageshack.us/img19/9533/bombafrenodiscov8.jpg

[oversite]

Thanks Disco.

Has anyone done this before?

[sheerluck]

I tried, but totally failed to pull one apart.

[460cixy]

This might be a dumb question but have you un done the fitting on the valve going to the rear and is there fluid there? Could be a colapsed hose on the rear or even blocked bleeders on the rear and may not be the valve at all

[oversite]

Yeah its not comming out of the valve, we have isolated that as a problem.

How has no-one done this before??

[460cixy]

If I had one here I would gladly pull it apart. Anyone want to donate one for dissection ? Maybe just try a wrecker and get a secondhand one

[clubagreenie]

Stupid idea but it's applicable for RRC so may also apply here.

There's a switch on the side of the master cylinder that, when you run out of fluid, holds the piston in a different position inside the bore and uses the second circuit on the fronts only. You only need to unscrew it and the piston will return to it's usual position. Won't leak any fluid.

[460cixy]

Stupid idea but it's applicable for RRC so may also apply here.

There's a switch on the side of the master cylinder that, when you run out of fluid, holds the piston in a different position inside the bore and uses the second circuit on the fronts only. You only need to unscrew it and the piston will return to it's usual position. Won't leak any fluid.


I was thinking about this but I would of thought it would part of the the prop valve it's self. But it won't have a effect on fluid flow what it does is detects a pressure differential between front and rear circuits and trips the light it won't open and close a circuit if all was well but the light needed reseting what your saying is correct

[sheerluck]

Yeah its not comming out of the valve, we have isolated that as a problem.

How has no-one done this before??

I have a brand new valve in the shed with exactly the same issue as you are describing. I was replacing mine as the original was leaking, plus I had replaced the brake hoses all round.

When I tried to bleed the brakes (mine's non-ABS) I got zero fluid through to the rear. I tried blowing some compressed air through, and nothing got through to the back.

I tried undoing the big bolt at the rear of the valve, but it pulled the vice off my bench instead! And after all the messing about, I just bit the bullet and bought a replacement.

[460cixy]

I have a brand new valve in the shed with exactly the same issue as you are describing. I was replacing mine as the original was leaking, plus I had replaced the brake hoses all round.

When I tried to bleed the brakes (mine's non-ABS) I got zero fluid through to the rear. I tried blowing some compressed air through, and nothing got through to the back.

I tried undoing the big bolt at the rear of the valve, but it pulled the vice off my bench instead! And after all the messing about, I just bit the bullet and bought a replacement.


Have you got the non functioning valve?

[sheerluck]

Have you got the non functioning valve?

Sure have ;)

Brand spanking new, apart from one aborted attempt at installation.

[460cixy]

Post it down and ile have a sticky beak

[sheerluck]

Post it down and ile have a sticky beak

Sounds like a plan. PM me some details and I'll chuck it in the post.

[460cixy]

Done. Ile strip it down and take some decent pics to post up and if I can get it functioning ile post it back . Hard part is getting the right size seals and orings to fit that are brake fluid compatable and I would near bet my left one thers no kits available but we have boxes full of odd orings and seals just takes hours sometimes to sort throu them all to get the right part this might not help the op but it may just help some one else down the track

[oversite]

Thanks heaps guys,

Im going away for 3 weeks and I was going to try to fix the problem before I leave but now Im going to wait unitll you have had a go then I will work on mine :p

[clubagreenie]

In the RRC at least, there's two circuits on the front brakes and the rears are connected to the primary front. The switch doesn't switch on pressure but on the piston location.

When you loose fluid in the primary circuit (fronts and rears) the pedal drops as the piston has no resistance. I can't remember exactly but I think there's a groove that catches the pin in the switch, turns the light on and stops the piston returning back past the orifice for the primary circuit and allows it to continue to operate the secondary circuit.

[460cixy]

It might be a week before I get to it

[clubagreenie]

Basically, unscrew the switch, the piston may click back into it's original position. As said, it won't leak any fluid and it's a 30 sec process to try. Hopefully it's that simple.

Check the rear output of the master cylinder and then higher up on the same circuit to see if the primary front circuit has fluid as well. If that's missing then there's a master cylinder issue. I've never had to "reset" a proportioning valve, ever, on anything.

[460cixy]

Going by this diagram the only switch is the fluid level Land Rover Workshop Manuals-300Tdi Discovery-BRAKE SYSTEM NON ABS (http://landrover.workshop-manuals.com/discovery300tdi/index.php?id=869)

[clubagreenie]

Looking through that ignore everything I've said. They changed the system, but I'll still look at the master cylinder first.

[oversite]

the problem is definitly in the distribution valve! the master cylinder was a problem and since I replaced it there is fluid flowing to the valve just not out the back of it.

[oversite]

so I fixed the distribution cylinder today :):):):):):):):):) and it was a really easy job. just pull it out, pull it apart, clean and re assemble and re install.

The most difficult job was getting the solid lines back into the damn cylinder!

Also the nut is on F-ing tight!

[460cixy]

Glad to hear that what did you find? I never ended up getting the valve off sheer luck so I never got to open one up

[oversite]

There is an internal plunger type thing with a spring bearing that only allows brake fluid to get to the rear when the bearing is compressed, when the rear runs totally dry there is no pressure and the plunder moves so the spring bearing isn't compressed.

Once you pull of the large nut on the end the plunger can be undone with a flat head screwdriver (just don't loose the small rectangular steel bit that compressors the spring bearing.) and I just done a good clean out with brake cleaner and replaced everything and hay presto-its all fixed!:)

To replace the unit was $250 recoed or $400 new so I guess alot of people have paid more then they deserve!