soft pedal

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Jul 21, 2003 | 05:50 PM

jayrus

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Joined: Jun 2003

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soft pedal

Hey guys,got a major problem here.I just did brakes on a friends truck because the pedal was going to the floor.It is an 84 F250,2 wd auto with the 6.9 diesel.We replaced the rear shoes,resurfaced drums,and replaced the front calipers.After bleeding the system the pedal felt great until we started it.As soon as its running the pedal gradually fades to the floor.We decided to replace the m/c and same problem.I know there is no air in the system,but the pedal still goes down.The truck stops fine,but if you keep pressing down on the pedal it keeps going.The drums are within spec and the rear shoes are adjusted correctly.There is also no fluid loss.Any ideas?We are at a standstill until we can think of something else.

Jul 21, 2003 | 07:07 PM

bigjon

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soft pedal

did you adjust the proportioning valve?

Jul 21, 2003 | 09:06 PM

85F_150driver

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Joined: Jun 2003

Posts: 390

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From: Rose City, MI

soft pedal

sounds like a booster problem to me check it for leaks at the hoses. if no leaks are found then take it off and inspect it for excessive wear.

Jul 21, 2003 | 10:37 PM

jayrus

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Freshman User

Joined: Jun 2003

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soft pedal

I didn't know the p valve was adjustable.I will check that in the AM.The booster seems fine.It can sit for a few hours and still holds vacuum.

Jul 23, 2003 | 06:56 PM

chornak

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Joined: Jul 2003

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From: detroit

soft pedal

Hey, I've got a '87 F-150 thats doing the same thing. I replaced the master cylinder, bled the brake and the pedle still goes to the floor if you apply light pressure to the pedle. I'm at the end of my rope. Anybody have a idea what to look at next?

Jul 24, 2003 | 05:23 AM

motorheadmach1

Senior User

Joined: Apr 2003

Posts: 159

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From: nowhere town nj

soft pedal

the best way i can think of to narrow it down is to find out if its hydraulic or power. with the key off and engine off puch the break pedal a few times to use vaccum reserve. than put steady firm pressure on the pedal. if it goes to teh floor than its hydraulic related. check proportioning valve and lines and things. check those front rubber lines they may be expanding.
if that test all goes well start teh truck and do the same thing this time disconnect the vacuum line or clamp it. the line to the booster that is. if the problem goes away that its gotta be your booster.

i have the same problem on my 86.i ned both a master cyl. and a booster.

Jul 24, 2003 | 08:34 AM

jtvon

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Joined: Jul 2003

Posts: 2

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soft pedal

Hi Guys,
I have the same problem, brakes worked fine before i had to replace my front calipers because the left one was sticking.
can't get pedal, bleed,bleed,bleed, new mastercylinder both new front calipers both new hoses. someone please tell me about this proportioning valve,should it be replaced also?
Thanks JV