i just recently purchased this 79 f100 it has the running gear out of a 78 f250 4x4. the PO bypassed the Proportioning Valve for some reason. it now has disc fronts with dual calipers and drum rears. he brake pedel goes to the floor when stopping. i know it needs front rotors and cant find any leaks. the resevoir is full. im wondering if the lack of the PV is causing some problems the old PV is still mounted they just put a line around it. i still need to check the drums havnt made it that far just wondering if i need the PV and if so i cant find one online. any ideas on one to use?

 

"Wildwood" has a great reputation. Wilwood High-Performance Disc Brakes - Porportioning Valves & Pressure Valves

 

Bypassing the disc/drum combination brake valve will not make the pedal go to the floor. This is a closed hydraulic system. As long as there are no fluid leaks or air in the system, fluid pressure will be the same throughout the entire system.

Things that will make the pedal go to the floor:

1. MC bypassing (internally) or, leaking out the back.

2. Air in the brake system.

3. Leaking brake components or ruptured brake hoses or hard lines.

4. Rear drum brake shoes not adjusted out.

It would be best to get the combination valve plumbed back into the brake system. It contains a metering (hold-off) function for the front disc brake circuit, a pressure differential sensing safety device that monitors the pressure between the front and rear brake circuits and, a proportioning valve that regulates pressure to the rear drums, in a panic stop situation.

 

Here's a pic of the mc and lines you can see what the did there. No body lift on this truck.

 

A little hard to tell from the lighting in the photo but, the brake booster looks like it's been (or is) wet from brake fluid. --don't know if it's coming out the back of the MC, from the lid or, both (?).


IF the MC is leaking out the back and getting fluid over into the brake booster, the booster would also have to be replaced.

Brake fluid will attack and deteriorate the booster diaphragm.

 

Yup. I think it has. I was showing the brake lines they stretched them for some reason the coils are not coiled

 

Possibly the truck didn't originally have a power brake booster. If it didn't and if the booster was added, the existing lines would have to have been stretched out to reach the MC.

My '69 F100 Ranger came with front drums (as all Bumpside F100s did) and it had manual brakes. I added a dual diaphragm brake booster from a '75 F350. I had to stretch the existing MC lines to reach the MC, since the booster spaced the MC further away from the firewall.

Before.



After.



I added the booster while I still had drum brakes all the way around. However, I knew that I would be fabricating new brake lines when I converted the front drums to discs and replaced the old conventional cast iron MC for a modern MC.

 

i like that setup where did you get the pro valve? after lookin g some more i will be redoing the brake lines also seam they stretched more that those two lines ill take pic tomorrow. is that mc off of ranger? in the 2000's

 

Thanks. The disc/drum combination brake valve is an NOS Ford truck valve I bought off ebay.

My MC is for a '95 Ford Explorer that I bought new through NAPA.