Need some brake help!
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Senior User
Joined: Feb 2010
Posts: 106
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From: Macon Ga
Need some brake help!
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?
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From: S/W Missouri, Polk county
"Wildwood" has a great reputation. Wilwood High-Performance Disc Brakes - Porportioning Valves & Pressure Valves
Lead Driver
Joined: Apr 2011
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From: El Dorado, Arkansas
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.
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.
Lead Driver
Joined: Apr 2011
Posts: 6,399
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From: El Dorado, Arkansas
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.
Lead Driver
Joined: Apr 2011
Posts: 6,399
Likes: 40
From: El Dorado, Arkansas
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.
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Senior User
Joined: Feb 2010
Posts: 106
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From: Macon Ga
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
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Lead Driver
Joined: Apr 2011
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From: El Dorado, Arkansas
My MC is for a '95 Ford Explorer that I bought new through NAPA.
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