1arunem

1965 442 with power brakes (has front discs which I was told are off of a 69 buick skylark).

Last time I drove the car, braking became difficult and I really had to stand on them to stop. Got home, noticed rear pot (small one which seems to be for front brakes) of the master cyl empty and could see evidence of a leak running down booster behind master.

I replaced master yesterday (bench bled it) and bled all four corners with no issue.

Went to test drive and noticed at first rear wanted to lock up. This seemed to stop after a bit of driving but stopping was still a chore and seemed as though all 4 were not doing their job. Car did not stop nearly as easily as it always has in the past.

Tried to re-bleed and I am getting next to nothing out of the rear bleeders. I noticed there is a small 'valve' that is 'in line' after the master cylinder and it has a 'button' with a rubber boot over it. Is this some sort of proportioning valve or something that could be faulty? It is in line off the front pot which goes to the rear brakes. I had my wife hold the brakes with the car in the air and I can freely spin the back wheels so the backs are not functioning.

Any ideas appreciated.

Picture of valve for reference. The 'button' with the boot over it is on the back side of the valve..

Thanks!!
Warren..

redoldsman

I would replace the hose going to the rear brakes. When these things get old they can block fluid. While you are doing that it is probably a good idea to replace both the front ones too. This ia a very common problem.

oldcutlass

I would also remove the rear wheels and drum to inspect the wheel cylinders for leakage and make sure they are not frozen.

joe_padavano

You need to understand a few things. First, trace the lines coming out of the M/C and you'll find that the FRONT reservoir feeds the front brakes and the back reservoir feeds the back brakes. FYI, the port with the larger tube plumbed to it is typically for the rear brakes.

Second, the valve you have is a metering valve and it is NOT a proportioning valve. The 1967-70 factory disc brakes did not use a prop valve but instead matched the front and rear piston sizes at the wheels to avoid lockup. All bets are off with a mix and match brake system, however. The metering valve is only intended to delay application of the front disc brakes to give the linkage in the rear drums time to take up any slack. Again, the system as you have it plumbed is how the factory did it for 1967-1970 cars.

Third, you do have a distribution block with a differential pressure switch. The dist block has an internal piston that slides one way or the other if you have low pressure in half the system (either due to a leak or an air bubble). If you pushed this piston all the way to one side while bleeding the brakes, it will block the flow to that side - the rear in this case. You can try to reset it by cracking a bleeder on the front and pressing on the brake pedal. This creates higher pressure in the rear and should push the valve back to center.

Fourth, definitely replace the hose to the rear brakes if it is old. I assume the front hoses were new when the disc conversion was done.

jaunty75

I had this exact issue with the brakes on my '78 Toro. No fluid to the rear brakes. The problem was exactly what Mr. P suggests. I replaced the rear brake hose, which might very well have been the original, 39-year-old hose, and life was good again.

1arunem

Thanks guys. Replacing rear rubber hose is next on the list.