Hi all, I just got my 48 F-6,it had no brake fluid so I filled the master cylinder pumped the brake pedal a few times and got a full pedal...and it does not move from the full position,rear brakes seemed to be locked, now keep in mind that I do concrete flat work for a living that said any idea's?Griff52

 

The first thing I would do is to locate the bleeder fittings on the wheel cylinders and soak them in penetrating oil for a day or so. Then I would crack each one open while a helper pushes on the brake pedal. Fluid should come out and the pedal should go down some if the master cylinder is operating and there are no blockages in the system. But you may have to completely remove the bleeder fittings if they are plugged with rust ond dirt.

 

That may not "fix" it if your wheel cyls are frozen and your drums are worn enough to not allow you to "unlock" the drums from the hubs....

You may have to drill out the bleed screws and somehow pry the shoes (and wheel cyl pistons) inward enough to get the drums off.

Then you can replace/rebuild the wheel cyls.

 

Griff52~
Action shots of you working on your truck are welcome... or just of your new truck. Congrats on getting it home.

 

I did bleed the right rear and that seems to free up the brakes but as soon as I step on the pedal it locks up again,opening the bleed plug releases the brakes again so I should be able to remove the drum and take a look. Thanks for your help..and as soon as I can steal my camera back from my daughter I'll take some pic's

 

It sounds like the master cylinder is not letting fluid return,try cracking the line at master cylinder to release brakes .the plunger may not br returning all the way.

 

Before you get ahead of yourself, if the MC was dry, then you need to bleed the entire system. Bleeding only the right rear doe s you no good getting the system bled. You should have the brake system with the booster (behind the MC) and if so, you must bleed the booster first.
Start with bleed screw #1 (on the end of the booster body), then bleed screw #2 (on the wheel cylinder connector pipe) Do this with the engine OFF and no vacuum in the system.
Then bleed each wheel cylinder.

 

Griff52~
Here's the procedure (with pic) for bleeding a brake system with a booster. It's parked over at the Large Truck Forum in the Tech Folder.
https://www.ford-trucks.com/forums/8...ke-system.html

 

Hi All,tried bleeding brakes only had one bleed screw on booster,once the truck is started
brakes lock up, at that point I have to release pressure at each wheel cylinder so truck will roll freely. Is there a check valve some where that needs to be replaced? And again thanks!!

 

Griff,

Does your truck have new brake hoses? If not if you have one or more old hoses they can act as a check valve. They get old and close up on the inside. The pressure from the MC will force the fluid toward the wheels forcing the hose to open but the back pressure from the wheel isn't enough to force it open on the return. Even if the hoses look good on the outside if they're old or poor quality the inside could be swollen shut.

 

I will bet they are original,when it stops raining I'll replace them with new hoses probably due for them any way and that will remove one possible problem. Thanks

 

When I did the brakes on my 55 F-600, I replaced all 4 flexible brake lines. I also thoroughly flushed the rigid steel lines.

Later, I'll do the dual reservoir split system and then it'll get all new stainless steel lines.


Cheers,


Rick