Air in break system....
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Junior User
Joined: Jan 2006
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Air in break system....
I recently replaced all the read break lines in my 82 F250. They rotted out and caused the break fluid to completely drain from the master cylinder. I also replaced the vacuum booster and master cylinder at the same time. I bench blead the master cylinder, and blead all the air out of the rear lines, starting with the rear right, then rear left, then front right and finally front left. After doing this several times I still can't get a "firm" feeling pedal. In looking at the proportioning (SP) valve, at first i found what I thought was a bleeder screw, but after looking at it closer i'm not sure. It looks like a plug typ fitting with a small ball bearing in the middle. I couldn't find any procedure for bleading the proportioning valve. I'm guessing there is some air trapped in there, but i could be wrong. I have done quite a bit of break work on newer cars, but i can't get this worked out. Anyone have any ideas or tips about this? Thanks!
Post Fiend
Joined: Jan 2004
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From: Northwest, Arkansas
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Senior User
Joined: Apr 2005
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There is no bleeder in the proportioning valve. If there is air in there, then it will come out with bleeding. The first thing I would check is the adjustment of the brakes in the back. If the shoes are expanded by the adjuster to provide a very slight drag, then you will not get a firm pedal. Raise the rear of the vehicle and remove the plug on the backing plate. Use a screwdriver, or brake adjusting tool if you have one, to adjust the brakes. As you spin the tire, turn the adjuster out until you hear a slight dragging of the brake shoes.
Let us know if this helps.
Let us know if this helps.
New User
Joined: Jan 2006
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Here is a suggestion for bleeding your breaks that has always worked for me when I had trouble getting a firm pedal. Remove the master cylinder cover and fill with fluid. Crack all four of your bleeder screws open to the point that you are getting a single drip out of all four. Let it drip for as long as you like, but at least a half hour while keeping the master cylinder full. Don't have to pump the brakes to bleed this way, gravity does all the work. When done close all the bleeders and top off master cylinder and put cover back on. You should have a good pedal now.
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Junior User
Joined: Jan 2006
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Can anyone tell me what the little valve looking thing under the rubber boot cover is on the proportioning valve? Also, i read on another post about a pin that needed to be removed to blead a proportioning valve. I looked again and can't find it now. I'll check the rear breaks for adjustments and let you know what i find. Thanks for the replies!
