Rear Brakes

[stimlin]

On my 95 ATX I am about to replace the calipers, rotors etc on both rear wheels. I have noticed a small "box" type thing with a spring on it that is mounted to the frame of the car on the drivers side near the rear axle, it has what appears to be the four brake lines running into it. It also appears to be leaking fluid and it looks like the springy thing is basically non functional.
What exactly is this part? I have read in posts in the past, "brake proportioning valve"?
What does it do? Does anyone here know the part number and availablity from FORD for a replacement?


Thanks!!!

STimlin
[email protected]

 

[JEM]

Yes, this is the load-compensating valve for the rear brakes. Under full braking with a light load it pretty much disables the rear brakes completely, the rest of the time it allows about 30% (guesstimate) of line pressure to the rear brakes.

When you say 'the springy thing is basically non-functional' - the spring is just there to keep the suspension motion from breaking the valve, most of the time it is (and is supposed to be) pretty loose.

I have no idea what the Ford PN is, or whether it's even available any longer, but as far as I know it's the same part on all rear-disc Tauruses from '88-95.

 

[stimlin]

Thanks JEM
I think I'll be able to get one from the local junk yard. I'm not really sure if the existing one is working or not, it looks pretty beat and has got a slight leak, but I figured I might as well replace it while I am doing the brakes anyways.

Now my problem is the drivers side emergency brake cable...I do not have enough slack in it to get it back on the caliper spring.
Any suggestions there?

Yes, this is the load-compensating valve for the rear brakes. Under full braking with a light load it pretty much disables the rear brakes completely, the rest of the time it allows about 30% (guesstimate) of line pressure to the rear brakes.

When you say 'the springy thing is basically non-functional' - the spring is just there to keep the suspension motion from breaking the valve, most of the time it is (and is supposed to be) pretty loose.

I have no idea what the Ford PN is, or whether it's even available any longer, but as far as I know it's the same part on all rear-disc Tauruses from '88-95.

 

[itwonder]

The load compensating valve is simple to disassemble and clean, once removed from the car. The way it works is when weight is added to the trunk, the rear end squats, which makes the rear control arms move toward the body. That movement acts upon the compensating valve through a spring and lever. The lever presses against two small pistons in the valve so more fluid is allowed to pass through the valve the harder the lever pushes on it (increasing weight). The piston moves only a fraction of an inch.

The usual problem is the spring and lever become corroded, and/or the pistons become stuck due to gum and corrosion. Since the car spends most of its time unloaded, they usually end up getting stuck in that position. Thus, fluid flow to the rear brakes is inadequate. This can cause calipers to fail to release properly, or poor rear braking.

The adjustment rod on the compensating valve lever has a threaded section that is used to set up proper operation of the valve. This is covered in the FSM, but really it is best to just set it tight so that the valve is open all the time.

You did not mention the rubber brake hoses, but you should definitely change those out as part of the job. It is common for them to look new from the outside, but they often develop restrictions on the inside that cause all kinds of trouble.

 

[Storm-Chaser]

The Service Manual refers to the proportioning valve using a number of different terms. including Brake Combination Valve, Brake Load Sensing Proportioning Valve, Brake Pressure Control Valve, Brake Pressure Differential Valve, Dual Load Spring Valve, Proportioner Valve, Proportioning Valve, and Rear Brake Proportioning Valve.

The part is obsolete from Ford and no longer available. You should be able to find one will a little effort, but you should be able able to find a used one in good condition. Ford Dealer List for the proportioning valve was $110 and change the last time I checked.