brake part name ?
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Senior User
Joined: Sep 2002
Posts: 126
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From: staunton
brake part name ?
I need to know the name of this part I need, could any one help. This part is located under driver side door bolted inside the frame on a 77 F-150 4x4. the brake lines come from the master cylinder into it and then go out of it to the back I think. it kindda looks like a large slave cylinder for brakes or something (although I dont think it is a slave cyln). it has 4 brake lines hooked to it and a power supply. any ideas. THANKS
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Joined: Sep 2001
Posts: 30,255
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brake part name ?
If the part has another branch to the casting almost opposite the "power supply" it is a proportioning valve, if it does not have that extra branch it is a differential metering valve.
The "power supply" is a switch that activates your brake failure light. If a rear brake hose blows the differential valve spool shifts and seals off the rear brake system and activates the switch. If a front brake line fails it seals off the front brakes etc.
The proportioning valve unit does the same light activation, seal-off, and also reduces the pressure to the rear brakes to help avoid rear brake lockup.
The "power supply" is a switch that activates your brake failure light. If a rear brake hose blows the differential valve spool shifts and seals off the rear brake system and activates the switch. If a front brake line fails it seals off the front brakes etc.
The proportioning valve unit does the same light activation, seal-off, and also reduces the pressure to the rear brakes to help avoid rear brake lockup.
Elder User
Joined: Feb 2002
Posts: 987
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From: East Bend, Carolina, U.S
brake part name ?
Just curious, but how is it possible to bleed a brake system if the differential metering valve can shut off front or rear brake system that has a blown brake line? Bleeding brake system should create the same condition shouldn't it?
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Posting Legend
Joined: Sep 2001
Posts: 30,255
Likes: 37
brake part name ?
Yes it can and that is what messes up a lot of brake systems. That is why I recommend a vacuum brake bleeder to bleed the brakes. Many people push on the brakes b4 the bleeder valve is released which can add to the problem.
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