Brake proportioning
Elder User
Joined: Feb 2001
Posts: 657
Likes: 0
From: brimfield township,OH
According to my manual,the valve is a little fitting bolted to the master cylinder before the brake line.I was kinda wondering the same thing myself.My brakes on my truck really suck.The last time I had a problem like that it was the prop valve.Those used to be nice sized units with a nice price tag.
Posting Guru
Joined: May 2007
Posts: 1,208
Likes: 2
From: North Reading Mass
Ford truck brakes ae usually pretty good. Make sure the self adjusters in the rear are working. Don't be surprised if you find the original factory brake shoes still there! I had to replace a master cylinder and booster and the odd brake line but have had no problems withwheel cylinders, calibers, or the proportioning valve.
The front brakes do about 70% of the braking on a unloaded pickup so a weak rear brake system might not be detected. Performance can also be affected by old contaminated fluid or air in the system.
I always do a complete inspection and brake pad/shoe replacement when purchasing a vehicle. Its a good way to find out about other problems, in my case a bad rear axle seal and ball joints.
regards
rikard
The front brakes do about 70% of the braking on a unloaded pickup so a weak rear brake system might not be detected. Performance can also be affected by old contaminated fluid or air in the system.
I always do a complete inspection and brake pad/shoe replacement when purchasing a vehicle. Its a good way to find out about other problems, in my case a bad rear axle seal and ball joints.
regards
rikard
FTE Legend
Joined: Jun 2006
Posts: 31,930
Likes: 1,499
From: Ottawa, Ontario
There is a proportioning valve on the frame if I'm not mistaken. Besides the rear drums that never stay properly adjusted, the front caliper sliders are known to sieze and this drastically reduces braking power.
Postmaster
Joined: Oct 2008
Posts: 3,026
Likes: 0
From: Renton, WA
if it's like mine there isn't actualy a proportioning valve. there's a fitting between the rear line and the master on the side of the master. It is actually just a calibrated restictor to "slow" the rear brake application.
most vehicles don't have true proportoning valves, the blocks on the frame are saftey valves to turn on a warning light if there is a leak and a loss of pressure on one side.
The proportioning is enginered in with the sizeing of the brakes
most vehicles don't have true proportoning valves, the blocks on the frame are saftey valves to turn on a warning light if there is a leak and a loss of pressure on one side.
The proportioning is enginered in with the sizeing of the brakes
Cargo Master
Joined: Jan 2004
Posts: 2,512
Likes: 8
From: Cook Forest and Irwin PA
Trace your lines. the front (using a large factory fitting - or aftermarket adaptor on a 3/16 line) squirrels around and should go to a T fitting on the drivers side, and then cross under the engine to the passenger side.
the rear lines drop to the rabs unit located on the frame under the cab, and then run thru horribly rusty pipe to the rear flexihose.
Ford changed the brake M/O sometime in the late 80's, circuit isolation was accomplished in the master cylinder along with a fluid level indicator.
A true proportioning system would be located on the rear with a ride height sensor - if the rear of the car comes up (severe braking, nose dive) then a mechanical valve literally limits the rear pressure to avoid lockup - even on 4WABS systems (the ford tarass same year is a good example)
the rear lines drop to the rabs unit located on the frame under the cab, and then run thru horribly rusty pipe to the rear flexihose.
Ford changed the brake M/O sometime in the late 80's, circuit isolation was accomplished in the master cylinder along with a fluid level indicator.
A true proportioning system would be located on the rear with a ride height sensor - if the rear of the car comes up (severe braking, nose dive) then a mechanical valve literally limits the rear pressure to avoid lockup - even on 4WABS systems (the ford tarass same year is a good example)
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Post Fiend
Joined: Jan 2005
Posts: 8,402
Likes: 10
if it's like mine there isn't actualy a proportioning valve. there's a fitting between the rear line and the master on the side of the master. It is actually just a calibrated restictor to "slow" the rear brake application.
most vehicles don't have true proportoning valves, the blocks on the frame are saftey valves to turn on a warning light if there is a leak and a loss of pressure on one side.
The proportioning is enginered in with the sizeing of the brakes
most vehicles don't have true proportoning valves, the blocks on the frame are saftey valves to turn on a warning light if there is a leak and a loss of pressure on one side.
The proportioning is enginered in with the sizeing of the brakes
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