80 F100 Brake Problems
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Senior User
Joined: Oct 2004
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80 F100 Brake Problems
I have a 80 F100 that I just got running again after sitting for about 5 years. When I stepped on the brake the pedal went to the floor and I heard the sound of air being pushed out. I checked the cylinder and the fluid was low so I filled it up. I then continued to step on the pedal but it kept going to the floor and I heard the same sound. I checked the fluid and the level didn't go down. I had the pedal on my 93 F150 go to the floor before but I found a broken brake line. I don't see where it may be leaking on the F100 so I think it may be the booster. Anyone have any suggestions on what I should check?
Elder User
Joined: Apr 2009
Posts: 922
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From: San Diego
I had a similar problem where I could hear an air sucking sound when the brake wasn't being pushed and it ended up being the booster. I would try to bleed the brakes, you could have a major bubble in there somewhere, and check each of the wheel cylinders for leakage, if that doesn't work then replace the booster.
The one I had a problem on, looked like the booster was original (rusted to hell). Replaced it everything worked great after... real easy, remove two bolts from master cylinder (you don't have to disconnect any brake lines, just find a way to support the MC so the brake lines don't get bent) then there are four bolts holding the booster to the fire wall and a clip holding the brake pedal to the actuator... really easy to swap and not too expensive, unless you have someone else do it.
The one I had a problem on, looked like the booster was original (rusted to hell). Replaced it everything worked great after... real easy, remove two bolts from master cylinder (you don't have to disconnect any brake lines, just find a way to support the MC so the brake lines don't get bent) then there are four bolts holding the booster to the fire wall and a clip holding the brake pedal to the actuator... really easy to swap and not too expensive, unless you have someone else do it.
Post Fiend
Joined: Jul 2004
Posts: 8,786
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From: Northern California
The Four bolts holding the booster to the firewall are inside the cab.
You also have to disconnect the brake pedal and brake light switch.
As said above, not too difficult.
Also with the booster off, check the firewall for cracks. The 1980/ early 81 was factory recalled for the possibility of severe cracks to the firewall due to flexing from the brake booster and/or clutch. A reinforcement repair kit was avaliable to fix the problem. If it has this reinforcement kit, leave it on. If it has cracks, they will need to be repaired. Do not know if they still make the kits to fix the problem. Probably not though.
If the fluid is black and dirty, I'd recommend a brake line flush, with new fluid.
Also of note, Brake warning lamp on? Porpotioning valve might be out of center, shutting off the brake fluid to one axle.
You also have to disconnect the brake pedal and brake light switch.
As said above, not too difficult.
Also with the booster off, check the firewall for cracks. The 1980/ early 81 was factory recalled for the possibility of severe cracks to the firewall due to flexing from the brake booster and/or clutch. A reinforcement repair kit was avaliable to fix the problem. If it has this reinforcement kit, leave it on. If it has cracks, they will need to be repaired. Do not know if they still make the kits to fix the problem. Probably not though.
If the fluid is black and dirty, I'd recommend a brake line flush, with new fluid.
Also of note, Brake warning lamp on? Porpotioning valve might be out of center, shutting off the brake fluid to one axle.
Post Fiend
Joined: Jul 2004
Posts: 8,786
Likes: 28
From: Northern California
I agree with Franklin, most likely brake booster.
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