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1979 F150 brake problem

ColoradoJeepXJ

NAXJA Forum User
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I’m a jeep person and as much as I tried, my son owns a Ford. Oh well..... He has a 1979 F150 4x4 with a brake problem. When braking, the truck will stop but the pedal will go almost all the way to the floor. When you hit the brakes hard, the wheels will not lock up but the truck will stop.

Any ideas?
 
Bleed the brakes. Check the flex hoses for bulges.
 
Thanks for the response. The brakes were working and I hadn't opened the system so I didn't think bleeding would help. I will try it tonight. The truck has been having some vacuum issues so I thought it might be the vacuum assist. Not sure how to check to see if it is bad or what the symptoms of a bad one would be.

Again, thanks for the help.
 
The brake system has air getting into it somewhere. Bleed the brakes and check for leaks. It may be a very small leak if the truck has been sitting for a while.

Checking the vacuum assist is pretty easy. With the truck turned off pump the brakes until you get a firm pedal. Hold the brakes and start the engine. If the pedal moves when the truck is started, then the vacuum assist is working.
 
Well, I bled the system last night and it helped. I still think it feels mushy and the pedal travels too far.

What else can I do?
 
Are all the drums in proper adjustment? (don't know Fords, is it disc front/drum rear, or 4-wheel drum?)

After my last wheeling trip, I noticed my brake pedal going further down before I felt any braking. Turned out the self-adjusters in my rear drums were totally gummed up from dirt/mud and inoperative.

A good cleaning and adjustment later, much better pedal feel.

Rob
 
Disc front, drum rear. The rear self-adjusters are where I started. I have done a few things since then so I guess I’ll double-check them.

Thanks for your response.
 
I'm away from home for a little more than a week to go, but just for reference, somewhere back home I have the FSM for the 79 F series (I had a 78 F 150 and that was close enough). I'm not ready to get rid of it, but if you need specific info from it at some point feel free to PM me. I can either look stuff up or, for short sections I can probably scan to a PDF.
 
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