Brake Valve Question

[KenFro]

Good explanation Jim, Here's a question for you. On my 69 Camaro (power front disks, drum rears) I replaced M/C, rear lines and wheel cylinders. I then put new pads all around. When bleeding the rears I could not get pedal to go to the floor, but will on the fronts. Also the rear shoes would not move. I bench bled M/C again, bled the lines at the M/C bleeders, and bled rears and fronts several times. I now get some movement at the rear shoes, but still the pedal won't go to the floor. Could I have "tripped" the proportioning valve by pedal-bleeding the empty rear lines and wheel cylinders? If so how can I re-center it? It seems to have a button covered by a rubber boots on the rear, but I have read different definitions of what that button is for or how to use it, and some people insist that this is NOT a proportioning valve. If your not familiar with Camaros here's what this part looks like: Camaro Camaro Proportioning Valve & Bracket Set, 1967-1969 - Rick's Camaro Parts (http://www.rickscamaros.com/camaro-proportioning-valve-and-bracket-set-1967-1969.html) Any suggestions? Thanks!

[CPPAaron]

The valve that you are showing us from Ricks is called a Metering Valve and it’s different from the Proportioning Valve. This valve can not under normal conditions get stuck, this valve should help bleeding the rear brakes, this valve slows the flow of brake fluid to the front, by doing that you basically increase the flow of brake fluid to the rear. I would not mess with this valve unless you are having front brake issues.

Factory Camaro’s should also have another valve, this valve will have both the front and rear lines plumed thru it, this valve is called a Pressure Differential Switch! It is possible for this valve to get stuck and restrict fluid flow and can be centered with a small paper clip and can be test to see if it’s stuck with a simple test light.

[KenFro]

Aaron,

How would I reset the pressure differential switch “with a paper clip?”

Thanks,
Ken

PS: Rick’s angrily defends their catalog’s description of that part as a Prop Valve. Other people have called it a hold off valve.

[CPPAaron]

Aaron,

How would I reset the pressure differential switch “with a paper clip?”

Thanks,
Ken

PS: Rick’s angrily defends their catalog’s description of that part as a Prop Valve. Other people have called it a hold off valve.


The reseting with a paperclip is only with the later prop valve.