Ok, 1969 Cougar XR7 with disc brakes. New master cylinder, new distribution block and proportion valve. I cannot get fluid to the rear brakes, front brakes ok. I bled the master cylinder. I bought the tool for the distribution block to center the piston. I opened the front of the distribution block and pushed the piston to the back. Inserted the tool till it was snug. Pushed the piston back while trying to screw the tool in. When the piston went back far enough I was able to feel and screw the tool further in. Piston now will not move either way so I am assuming it is in the right position. I still cannot get fluid to the back. I disconnected the line at the rear axle so it does not go into the rubber tube. I cannot get fluid to come out. Really at wits end and want to sell or smash this car.. sorry, a bit angry right now.. I just do not see why fluid won’t go to the back. Lines are all good no issues. Thanks for your input.
I feel your pain. Let start at the line that goes to the rear. On the master cyl. loosen the line to the rear & see if you get fluid. If yes, ya know… If not Mast cyl…
On the other side of the issue it the possibility of the spool valve issue, but it should not stop fluid going to each axle. The spool has a V notch that the switch sits in. You can see it looking down into the switch hole. That,s the correct position. Not sure where you ended up when you “pushed the piston to the back”. Try the visual if needed for that issue.
I can get fluid out of the master cylinder.
I pushed the spool valve all the way to the back, then inserted the tool to a snug fit. Pushed the spool valve backwards till I could feel the tool tighten down into the V notch.
Ok, fluid at master cyl, but not at rear hose.
Steel line is rusted/plugged. Kinda a pain to replace, but pull drive shaft for best access.
Thanks, I’ll give it a shot..
What about disconnecting the brake lines from both wheel cylinders and from the proportioning valve and try blowing air from front to back to see if the rear line is clogged.
What I was thinking, but I am going to take it off and inspect it and then do that. Car is mostly rust free and original. All the other lines are original and usable. But I guess my luck would be this one is bad.
We’ve all been there. You sort of know what the problem is but it is such a pain that you really don’t want to deal with it. The good news is that once you fix it you can forget it.
Did you verify that the MC pushrod length is properly adjusted? If the pushrod is too short, you will not get the full piston stroke and may not be pushing enough/any fluid out of the front MC bowl.
This will not be evident during bench bleeding. Based on variability of MC and Booster design, the rod needs to be measured / adjusted whenever these components are swapped
Car was all together. I did replace the master but see no reason why the MC pushrod would need to be adjusted.
Question though: Before I go and pull the intermediate line off, if it was plugged/clogged wouldn’t my brake pedal be firm? With front caliper bleeders closed. Pedal goes to the floor all the time and does not build pressure.
Did you adjust your rear brakes up tight prior to bleeding
The rear brakes need to be bled before the front brakes. Likely the rear line is clogged and needs to be replaced with a new one. The lines often look fine but they rust from the inside so the last thing that is wrong is the outside.
Have you checked / replaced the soft line at the rear axle?
Worst case, you can disconnect it and see if you get fluid to bleed at the back end of the long hard line.
Yeah, did that. Can’t fluid to come out the intermediate line.
The total piston stroke on most master cylinders is under 1 inch, so even a slight misadjustment of the pushrod can result in too much / too little movement of the master cylinder piston. If the rod is too short, the piston doesn’t provide a full stroke for the rear brakes.
Ford made the pushrod easily adjustable because no two master cylinders are exactly the same, particularly with aftermarket units. The castings may vary, as can the design of the piston, depth of the piston cup, and the resting position of the piston cup in the bore.
Checking the adjustment of the rod is free and takes less than a half-hour. You checked and changed everything else, why not take a moment to verify this critical item?
How would I check to see if the pushrod is the correct length?
Hi Mike,
There is a detailed procedure (with full measurement specs) in the Ford shop manual.
It involves measuring how far the pushrod extends from the Master Cylinder mounting flange on the booster and comparing that measurement to the depth of the MC piston cup from the mounting face of the master cylinder.
The pushrod is adjusted by turning the threaded end in or out and securing the adjustment with the lock nut.
If you are careful, sometimes you can separate the master from the booster and take measurements without removing the brake lines.
Thank you I appreciate the input.
You’re welcome - I know how frustrating these kinds of problems can be. Hoping you get it solved Mike.
I adjust the pushrod length every time I install a new booster - those are normally adjusted wrong. The master cylinder needs to be bench bled or no fluid will come out of it.