Proportioning Valve

[1993BlackSHO]

Ive searched on this and I can not seem to find out exactly what I need to know.

Trying to get my car road worthy, and the brakes were just scary. So new pads and rotors all the way around and went to bleed them to get new fluid in there and any bubbles out. The front is no problem. Went to do the RR and with my wife holding down the pedal, I only got a dribble out. Now the LR is on the ground still so the PV should not be an issue here. Im thinking bad line, so on the the LR. Using a jack to hold the suspension up, I have nothing on this side. The pad wont even compress at all with good pressure from the pedal.

So I take a closer look at the PV. Where exactly is the mechanism here. I see a pin at the top and bottom, and two rubber nubs in the middle. I can not see anything moving on mine that would cause this to work. I'm thinking it is frozen or something. What should I be seing? I can replace both lines pretty cheap, but the PV is not so cheap.

 

[Storm-Chaser]

Search is your friend . . . .

 

[1993BlackSHO]

Thank you, but I did find all this info while searching. I already changed one of the front hoses because it had failed. I will probably change both the rears just for good measure. I am not new to working on brakes. Been doing my own for 18 years.

But my question still stands. How does the PV operate? I just am trying to find out if I can see it working.

 

[naval-avi8or]

Ive searched on this and I can not seem to find out exactly what I need to know.

Trying to get my car road worthy, and the brakes were just scary. So new pads and rotors all the way around and went to bleed them to get new fluid in there and any bubbles out. The front is no problem. Went to do the RR and with my wife holding down the pedal, I only got a dribble out. Now the LR is on the ground still so the PV should not be an issue here. Im thinking bad line, so on the the LR. Using a jack to hold the suspension up, I have nothing on this side. The pad wont even compress at all with good pressure from the pedal.

So I take a closer look at the PV. Where exactly is the mechanism here. I see a pin at the top and bottom, and two rubber nubs in the middle. I can not see anything moving on mine that would cause this to work. I'm thinking it is frozen or something. What should I be seing? I can replace both lines pretty cheap, but the PV is not so cheap.

The two rubber nubs are the actual metering valves.

 

[1993BlackSHO]

OK so should I be able to see them move in and out? From what I can see they are not moving. Looks like they might be stuck all the way in. If thats the case, then changing my lines should give me rear brakes again, but no metering in a hard stop. But I guess the ABS will kick in if needed.

 

[hawkeye18]

FWIW, the brake bias valves that http://www.shobrosgarage.com sell do the exact same thing. It sends full pressure to the rears. It can be exciting when pushed very hard, but mostly just decreases your stopping distances.

 

[Storm-Chaser]

Thank you, but I did find all this info while searching. I already changed one of the front hoses because it had failed. I will probably change both the rears just for good measure. I am not new to working on brakes. Been doing my own for 18 years.

But my question still stands. How does the PV operate? I just am trying to find out if I can see it working.

Well, then you should be able to identify where the constriction is, based on that post. Simply bleed test both sides of the proportioner valve, like I describe to bleed both sides of the brake hose, and that will tell you if the proportioner valve is the problem.

Btw, if the poportioner valve is bad or malfunctioning, bias plugs may not correct the situation, and may serve to compound the problem.