I sure hope someone can assist me with this problem. I have a 1975 F250 Supercab, 2wd, 390, 4bbl with front disks and rear drums (HD).

Back in december 05, I had a fairly major brake job done.

-New front rotors, pads, bearings, etc.

-New rear shoes and hardware.

Considering the cost, I thought my problems had been solved, however I was wrong. Since the work was done, I have been back to the shop for an adjustment, and again today I had to return to have them adjusted, although this time was not as successful.

The problem is this, when applying the brakes, the pedal slowly goes to the floor. At a stop, the pedal will go all the way with only gentle pressure applied. Rounding corners with the brakes applied seems to amplify the problem as the pedal goes to the floor much faster. If I had to make an emergency brake application, I'm not sure it would work. The brakes will work fine with a little pumping of the pedal, but even I know this is incorrect.

The fluid is OK and there are no visible leaks. Therefore I would presume it's an internal problem. Could it be the wheel cylinders. If so what would be the problem? Can they be rebuilt or do they have to be replaced?

Thanks in advance for the help.

 

New wheel cylindars are about $10 each. I would check all your lines and master cylinder over and bleed the brakes starting with the wheel that is farthest away from the master cylinder.

Thats what I would do.

 

when you bleed the brakes do you have to pull out the little pin in the proportioning valve?

 

Try replacing the master cylinder, bench bleed the cylinder before it is installed. Flush out the entire brake system with new brake Dot 3 brake fluid. Here is the valve tool https://www.ford-trucks.com/user_gal...=94664&width=0 used to bleed the brakes.
Wheel cylinders will leak when they go bad.

 

Folks, thanks for the info.

Since the original post a couple of days ago, things have gotten a little worse. The pedal now goes all the way to the floor without difficulty. Once it gets there the truck will stop and the brakes will hold it, but the wheels would never lock up if they had to.

Thanks again, I'm going to start by checking the wheel cylinders and move up from there.

 

I strongly doubt it's the wheel cylinders. You have the classic symptoms of a bad master cylinder.

 

I agree, master cylindar. When you get a new one be sure to bench bleed it before you install it in you truck.

 

Thanks for the advice, I have one final question. Bench Bleed???

 

Use an old push rod or something that is long and has a round point, when bench bleeding your brake master cylinder. Make the master cylinder reservoir is about 3/4 full of clean brake fluid, and the two rubber hose coming out of the the port holes on master cylinder are submersed in the brake fluid during the whole bench bled process. Push in the piston on master cylinder, till it bottoms out, there should be no air coming out of the hoses when you have completed bench bleed process. Process should take about 45 minutes.

Here is the master bleeding section: http://www.classicperform.com/TechBook/BrakeBleed.htm

 

1. Try bleeding system RR,LR,RF,LF
2. Bleed through BLEEDER VALVES
3. Check lines n connections
4. CHeck master cylinder
Spongey brakes tends to be AIR in the system unless your Master is actually shot. Don't even mess with the porportioning valve.