brakes lockup when engine is started
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brakes lockup when engine is started
I have a 1987 f150 5L 4wd pickup.
The front passenger disc brake was locking up initially and looked rusty so I replaced both front calipers and pads. Everything OK for first spin around the block. then did emergency stop and brakes locked up and stayed locked. Bled brakes & drove home using emergency brake.
Pulled front wheels. Rotors spun. Started engine and watched the brake pedal depress by itself.
checked rotors and they stayed locked as long as the engine was running.
I searched some for related posts & tried loosening the master cylinder from the booster 1/4".The brake pedal dropped again and brakes still locked when engine was started.
Does anyone know what is going on and how to fix it?
Thanks
The front passenger disc brake was locking up initially and looked rusty so I replaced both front calipers and pads. Everything OK for first spin around the block. then did emergency stop and brakes locked up and stayed locked. Bled brakes & drove home using emergency brake.
Pulled front wheels. Rotors spun. Started engine and watched the brake pedal depress by itself.
checked rotors and they stayed locked as long as the engine was running. I searched some for related posts & tried loosening the master cylinder from the booster 1/4".The brake pedal dropped again and brakes still locked when engine was started.
Does anyone know what is going on and how to fix it?
Thanks
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New User
Joined: Feb 2012
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Thanks for the welcome, I've always been able to find the answers before just by searching, so didn't register.
I blockd vac, started truck - pedal did not depress. removed master cylinder attached vac and rod came out of booster about 3 inches.
will replace
thanks
I blockd vac, started truck - pedal did not depress. removed master cylinder attached vac and rod came out of booster about 3 inches.
will replace
thanks
Post Fiend
Joined: Nov 2005
Posts: 7,437
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From: Charles Town, W bygod Va
I believe you are talking about hydroboost.? (Just in case the OP wants to search the subject, or maybe someone will supply a link)
Fleet Mechanic
Joined: Jun 2011
Posts: 1,324
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From: Conway, South Carolina
That would be a good idea. But I am talking about a F350 booster/master cylinder. Like a booster/Master cylinder for a f350 with a 351w.
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SCRebel,
Would that be a straight forward swap, or require other changes? Which production years would work?
Thanks for the suggestion.
Would that be a straight forward swap, or require other changes? Which production years would work?
Thanks for the suggestion.
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Fleet Mechanic
Joined: Jun 2011
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From: Conway, South Carolina
There is two different type of boosters. I believe the shafts are different. Just make sure the get a f350 Booster that where the shaft that connects to your brake pedal is the same.
Its a straight forward swap. Just keep in mind it will take up more room. Also recommend f350 drum cylinders, and bigger calipers. But the booster and mater cylinder will make a great difference.
I am not sure about the years. I would get one for a 88-91. Same body style and everything was EFI in 1988.
The bigger calipers and cylinders will also make a big difference after the f350 booster/master cylinder.
Its a straight forward swap. Just keep in mind it will take up more room. Also recommend f350 drum cylinders, and bigger calipers. But the booster and mater cylinder will make a great difference.
I am not sure about the years. I would get one for a 88-91. Same body style and everything was EFI in 1988.
The bigger calipers and cylinders will also make a big difference after the f350 booster/master cylinder.
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Guys, I recently replaced the booster on my 87 F150, 4X4, standard trans, 302 and the brakes are "spungy". I blead the brakes (may need to do again??) but the front brakes dont seem to be doing much. The pedal pushes in a long ways before any braking happens and now the right rear lcoks up (drum).
Any suggestions
Thanks
Van
Any suggestions
Thanks
Van
Posting Guru
Joined: Apr 2011
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From: Hartland, WI
Guys, I recently replaced the booster on my 87 F150, 4X4, standard trans, 302 and the brakes are "spungy". I blead the brakes (may need to do again??) but the front brakes dont seem to be doing much. The pedal pushes in a long ways before any braking happens and now the right rear lcoks up (drum).
Any suggestions
Thanks
Van
Any suggestions
Thanks
Van
Was there fluid in/on the booster? And did you bleed the front and rear brakes? If theres fluid in the booster or on the front where the MC bolts up you have a leaking MC.
Senior User
Joined: Jan 2014
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From: Lincoln, NE
Guys, I recently replaced the booster on my 87 F150, 4X4, standard trans, 302 and the brakes are "spungy". I blead the brakes (may need to do again??) but the front brakes dont seem to be doing much. The pedal pushes in a long ways before any braking happens and now the right rear lcoks up (drum).
Any suggestions
Thanks
Van
Any suggestions
Thanks
Van
New User
Joined: Dec 2013
Posts: 3
Likes: 0
brakes spongy
I did notice a little dampness around the booster below the MC today. It may be time for a master cylinder
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