I am slowly bringing my 69 XR7 back to life and am working on the brakes (disc/drum). The pedal is spongy with lots of travel. I have the car on blocks, and the brakes stop the rear wheels, but not the front.
The lines have been flushed and all brakes bled and leak checked. The booster has been rebuilt by Booster Exchange. Brake pads and shoes replaced. Master cylinder and distribution block replaced with aftermarket by the PO, and there is no proportioning valve (is it really needed?). I could just shotgun and replace both the MC and block, but would like to know if I might be missing something. Your comments would be appreciated
Did you check or replace the front flexible lines connecting to the calipers? They do fail by collapsing in on themselves creating a very small ID. That happened on my 1969.
You state the system was messed with (after market) parts. This is most likely your issue. I would suggest starting at these parts. Correct mast cyl & dist block WITH the prop valve.
The Ford engineers had years developing & testing the system.
Suggestions by others would be a solution If your system was original.
Checking the flex hoses and caliper orientation are valid responses regardless of the brake components being used. Aftermarket parts can and do work just fine if specified and installed correctly. Buy cheap and you get what you pay for.
The hose & orientation were addressed by RESQCAT. The most likely issue was not, and they asked about the “missing” part.
As I stated these are the most likely problem.
The proportioning valve is needed. Without it the back brakes lock up long before the front discs ever do. The factory included one because it was totally necessary.
I’d pull the master and look at the rear to be sure it’s not leaking fluid. I just replaced one with the same deal. Especially if the PO installed it. Never trust the previous owner.
Thanks everyone for your suggestions.
Today I pulled the master cylinder to check for external leaks and found none. I then re-bench bled the master cylinder, verified the pushrod gap was at .020", reinstalled it, and bled the rest of the system. Fluid was a very pale yellow and showed no signs of contamination. I noted some minor improvement - after cycling the brake pedal multiple times, the front wheels became harder to turn, but I can still turn them if I apply a lot of force. But I cannot hear or see any caliper movement, which may be due to new pads that fit really tight. I also verified the calipers are in their correct positions, with the bleed screw on the top and facing to the rear of the car. The rear drums are working normally.
It’s no fun but I think the best way to test is to start at the master and follow the brake lines. You have some one push the pedal as you break loose the connection. You should see fluid coming out under pressure tighten the line before letting up on the pedal
I verified centering by observing the brake light - it comes on during prove out, and then off after the car is started, so I believe the spool is centered.
I rechecked the distribution block when I had the master cylinder out and could get a good visual - it is a newer version that incorporates a proportioning valve.
For reference, it is a MP VL3360.
My GTE had the original rear brake shoes still in it at over 154,000 miles. The rear brakes had never been very effective although they could be bled, and with a gauge did record correct pressures. What I ultimately found was that the rear distribution block on the rear axle was not drilled properly. There was an opening that would let fluid through but very slowly. Kind of like a second proportioning valve. This caused the expansion of the rear shoes to be much slower than designed. This is the only time I have ever even heard of such a problem. The only way I found it was by checking the flow at each connection all the way down the brake lines. I have also found a reproduction caliper that was not drilled properly on the bleed side. When you are looking for very elusive problems you have to go back to the most basic tests and assume nothing.
