Brake Issues
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Junior User
Joined: Dec 2004
Posts: 62
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Brake Issues
Hey there , I have a 1978 F-250 4x4 with brake issues. I installed new wheel cylinders, and springs with the old shoes in the rear. New bleeder screws in the front new line from proportion valve to the back. Now here is my problem, we bled it the old fashioned way and it seems to never get good pedal. After an hour of bleeding from the back rear to the front right in clockwise work we still can't really get a good pedal. I took it for a drive and have good brakes 2 times in a row then boom to the floor the pedal goes. I have to coast to a stop (in a huge field by the way) I feel like by looking that there is leakage between th MC and booster could this be my problem. If so is there a seal between there or should I just go by a new MC. thanks Dustin
Fleet Mechanic
Joined: Feb 2007
Posts: 1,326
Likes: 48
From: Middle TN
A couple of things could be wrong.
First make sure that the rears are adjusted properly.
If you had good brakes 2 times, then it went to the floor, could mean that the rear brake adjusters were not installed correctly or it was pushed out of place when you put the drums on. When you hit the brakes a couple of times the adjuster jumped off the brake shoe. Then you have no brakes.
Another possibility is like you think, that the master cylinder is failing. Usually they will hold as long as you push hard on the pedal, but slowly easing off with your foot pressure, the pedal will slowly go to the floor.
First make sure that the rears are adjusted properly.
If you had good brakes 2 times, then it went to the floor, could mean that the rear brake adjusters were not installed correctly or it was pushed out of place when you put the drums on. When you hit the brakes a couple of times the adjuster jumped off the brake shoe. Then you have no brakes.
Another possibility is like you think, that the master cylinder is failing. Usually they will hold as long as you push hard on the pedal, but slowly easing off with your foot pressure, the pedal will slowly go to the floor.
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Junior User
Joined: Dec 2004
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Thanks for the help, I haven't done anything more to the truck I did go and buy a MC since they are cheap. I checked the proportion valve and if you mean that plunger that you pull out to bleed the backs it wasn't tripped. I have been preoccupied with farming and hunting so its on the back burner for right now. I will let you know next week sometime. Thanks again for the help.
MSEE
Joined: Apr 2004
Posts: 10,386
Likes: 35
From: Austin, TX
Mark is asking if the valve is centered. The plunger you're talking about is to disengage the front brake proportioning piston when you bleed the fronts. If you see fluid between your booster and the MC, then you do need to replace the MC as it means the seal is on its way out which can let air in. Don't forget to bench-bleed it the proper way before installing it.
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Junior User
Joined: Dec 2004
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FIXED
Alright guys thanks for the help as usual. I adjusted the rear brakes, through the hole in the backing plate and put on the new master cylinder. I had a friend come out to bleed them and vwolla the old beast has like new braking. Thank you guys for your help now I just have to get the hard starting when hot issue fixed. At least it stops now!!!!
