Converting the 69 to single piston disc brakes. I have the correct hold off (well, 1970) and bracket.
Question,
Is there any special technique to bleeding the fronts with this valve in place. I'd think the old way of using gravity to get the fluid to the calipers wouldn't work with the valve.
Must you apply pressure to get fluid past the valve? There is nothing regarding this in the manual.
My 2 cents, when i bled my disc/ drum setup. I had to use a tool in the proportioning valve to allow the front to be bled.it fits in place of the switch.
Thanks Pete. I only have the 70 stock Distribution block that you circled, and will be adding this 69/70 featured, stand alone pressure metering valve (Aka, hold off valve).
It holds off the front discs until the rear drums play catch up so to speak.
In 1971 GM introduced the Combination valve, which combined the metering function of the 69/70 stand alone, with the brake pressure differential (waring light) and pressure isolation switch found in the old distribution block, and a new proportioning function that cuts the rears back proportionally in a heavy panic stop.
I've heard you need a special blocking tool that threads into the sender switch when bleeding a Combination valve as it trips and must be reset. I was frustrated years ago by this, for lack of that knowledge.
But now I'm thinking, have you had trouble bleeding the old Distribution block system? I've never had one trip and not return.
On the factory 69-70 units, all I have ever done is hold in the button while bleeding. The brakes always worked well on the four cars that I have or had with the single piston factory disc brake setup.
