Erratic braking problem
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Erratic braking problem
Greetings,
My 1996 F350 (diesel) has a brake problem I can't seem to get corrected.
Brakes Ok in the drive then when driven on the road and approach a stop brakes are soft and go half to three quarters of the way down. They do stop the truck but not quickly. Then when I let up and apply again, brakes are very firm then pedal goes down - lots of pressure required to stop the truck. Brake light is on.
I have replaced the master cyclinder, brake booster and put in new bleeders. Also bled all four corners multiple times with some air in the left front and not able to get any improvement.
Any help is appreciated.
Scott
My 1996 F350 (diesel) has a brake problem I can't seem to get corrected.
Brakes Ok in the drive then when driven on the road and approach a stop brakes are soft and go half to three quarters of the way down. They do stop the truck but not quickly. Then when I let up and apply again, brakes are very firm then pedal goes down - lots of pressure required to stop the truck. Brake light is on.
I have replaced the master cyclinder, brake booster and put in new bleeders. Also bled all four corners multiple times with some air in the left front and not able to get any improvement.
Any help is appreciated.
Scott
Post Fiend
Joined: Jan 2005
Posts: 8,402
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Two things spring to mind. First thing is you may have a vacuum leak or more likely a bad vacuum pump. If you can get a vacuum gauge on it a good pump should pull around 20in of vacuum. Low vacuum will turn the red brake light on.
Second thing is you say you have bled all four corners, however it is likely that you have the rear anti-lock brake system and so would need to bleed the RABS module after the rear brakes. The RABS module should be on the inside of the left side frame rail about level with the drivers feet. There is a bleed screw on it.
Second thing is you say you have bled all four corners, however it is likely that you have the rear anti-lock brake system and so would need to bleed the RABS module after the rear brakes. The RABS module should be on the inside of the left side frame rail about level with the drivers feet. There is a bleed screw on it.
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Lazy K
I tested the vacuum pump and found only 10 inches of vacuum
Time to replace.
Also managed to get the hydraulic abs unit bleeder loose and need to bleed that yet. Working by myself gets old....
Thanks for the help!
I tested the vacuum pump and found only 10 inches of vacuum
Time to replace.Also managed to get the hydraulic abs unit bleeder loose and need to bleed that yet. Working by myself gets old....
Thanks for the help!
Junior User
Joined: Sep 2009
Posts: 71
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From: Rochester, MN
I had a similar problem when I first got my truck and it was a
leaking line and/or wheel cylinder. (I say and/or 'cause my wrench
claimed he replaced a wheel cylinder but after taking the drum off
yesterday and seeing the mess that was there I kind of doubt it?)
I saw the line leaking...
good luck!
Jim
leaking line and/or wheel cylinder. (I say and/or 'cause my wrench
claimed he replaced a wheel cylinder but after taking the drum off
yesterday and seeing the mess that was there I kind of doubt it?)
I saw the line leaking...
good luck!
Jim
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Jim,
Thanks for the info.
I will start with pulling the rear wheels and drums and check it out. I may get away with a wheel cylinder(s) instead of a vacuum pump, but normally my luck turns to the worst case...
Scott
Thanks for the info.
I will start with pulling the rear wheels and drums and check it out. I may get away with a wheel cylinder(s) instead of a vacuum pump, but normally my luck turns to the worst case...
Scott
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