Brake Failure While Driving
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Elder User
Joined: Jun 2013
Posts: 685
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Brake Failure While Driving
Hello guys, I have a time sensitive question for you.
This morning I noticed that the brake pedal on my 1979 f150 was very stiff and did not stop easily. After about a mile the pedal softened up and stopped normally. Until about half way though my drive that is- I slid when turning from one road to another, only going around 20. Fast forward to this afternoon the truck will hardly stop. To get any kind of braking the pedal must either be pumped 5 or 6 times, or put completely to the floor. Both give a very slow stop.
The master cylinder had fluid in it. But only in the large space, it was full to the top. The smaller space was nearly dry.
As of now I am typing from work before I have to clock in and figure out what to do with the truck. Fill it up with fluid and drive slow? Tow it?
What parts should I check or have someone get for me on the way home?
1979 f150 4x4
400 NP435 NP205
power steering, power brakes
Dana 44 front disc brakes with new calipers and pads
9" rear with new wheel cylinders and shoes.
Brake lines look new and not rusty at all, but I did not put them on.
This morning I noticed that the brake pedal on my 1979 f150 was very stiff and did not stop easily. After about a mile the pedal softened up and stopped normally. Until about half way though my drive that is- I slid when turning from one road to another, only going around 20. Fast forward to this afternoon the truck will hardly stop. To get any kind of braking the pedal must either be pumped 5 or 6 times, or put completely to the floor. Both give a very slow stop.
The master cylinder had fluid in it. But only in the large space, it was full to the top. The smaller space was nearly dry.
As of now I am typing from work before I have to clock in and figure out what to do with the truck. Fill it up with fluid and drive slow? Tow it?
What parts should I check or have someone get for me on the way home?
1979 f150 4x4
400 NP435 NP205
power steering, power brakes
Dana 44 front disc brakes with new calipers and pads
9" rear with new wheel cylinders and shoes.
Brake lines look new and not rusty at all, but I did not put them on.
Laughing Gas
Joined: Aug 2010
Posts: 896
Likes: 55
From: Bothell
Sounds like you have a leak in the rear brake system and from the super stiff pedal you may also have a bad master cylinder and/or a bad proportioning valve.
I agree with harold, add fluid and bleed to find the leak first
I agree with harold, add fluid and bleed to find the leak first
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Elder User
Joined: Jun 2013
Posts: 685
Likes: 2
Alright guys, its been a frustrating time working on the truck. All lines are in great condition, new stainless lines and braided flexible lines without leaks. I put a new master cylinder on it, bench bled, and then bled it on the truck. However a new problem came up. The back brakes work great and the pedal feels great. The front brakes get hydrolocked after just a few min of driving. If I bleed the brakes the calipers release and all is good for another 1/2 mile. Would a p-valve be the cause of this? Where in the world do I get one of those? There are 6 different ones for dentsides. I have single piston caliper brakes.
More Turbo
Joined: Mar 2012
Posts: 515
Likes: 8
How old are the calipers? I had kind of a similar issue, except my front brakes would just drag pretty badly (not fully locked up) and release when bled. I replaced both calipers and the problem went away. Also, if you do end up replacing the calipers, try your hardest to find ones with metal pistons instead of plastic. I think I got mine with metal pistons from napa. Or maybe it was O'reilly's, I can't remember. Not sure about the proportioning valve though, sorry.
Cargo Master
Joined: May 2011
Posts: 2,387
Likes: 138
From: Northern California
If you changed your master cylinder you may have to adjust the plunger that is between the MC & the booster. If brakes are dragging after changing the mc this is the first thing i would look at.
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