Major Break Lock UP
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Joined: Jan 2007
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Major Break Lock UP
I have a 1975 F350 dump truck (hope to get some pics up soon) that had a major break lock up. We actually had to get a bobcat to lift the back end up and get me off the road cause I was blocking both lanes. Before the lock up I replaced both front break lines and got new front calipers (2 pistons). Bled and bled and bled them, dumped a load of top soil. Worked fine then BANG lock up. Pedal is rock hard, cracked front bleeder and it shot fluid over me. Could it be the poportioning valve? Any other ideas? Thanks for your help.
Hotshot
Joined: Apr 2009
Posts: 14,333
Likes: 247
From: Stanley, VA
Was it only the front brakes that were locked up or were the rears locked also?
And if it was just the front was it one or both wheels?
After you cracked the bleeder did the brakes release?
If it was just one wheel I would suspect first the caliper or installation, second the hose. Even though both have been replaced a deffective part is always a possibility.
Both wheels, I would suspect the proportioning valve first, then, remote posibility the master cylinder.
If it was all wheels were locked about the only thing I could think of would be the master cylinder.
And if it was just the front was it one or both wheels?
After you cracked the bleeder did the brakes release?
If it was just one wheel I would suspect first the caliper or installation, second the hose. Even though both have been replaced a deffective part is always a possibility.
Both wheels, I would suspect the proportioning valve first, then, remote posibility the master cylinder.
If it was all wheels were locked about the only thing I could think of would be the master cylinder.
Posting Guru
Joined: Nov 2007
Posts: 1,305
Likes: 2
From: Montgomery, IL
did you bled all 4 wheels or just the fronts? Maybe the proportioning valve got stuck based on only bleeding half of the system. I don't know about the dump trucks but on the pickups you are supposed to lock the proportioning valve in the OPEN position when you bleed the brakes.
What wheels actually locked up?
What wheels actually locked up?
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