Bake problems
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5th Wheeling
Joined: May 2021
Posts: 30
Likes: 10
Bake problems
OK guys. My son posted a question regarding his brakes on his 78 F250. Front brakes were tighting after a little while of driving to the point that the truck wouldn't move. We changed both flex lines and crossed our fingers. No luck! We bought the truck from an original owner that said that booster, master cylinder and calipers were original. (They looked it!). Truck has 107,000 original miles. Booster has given no assistance since we bought the truck. I went ahead and decided to replace all original parts. Booster, master cylinder, flex lines, and calipers. The problem still exists. Is it possible that the booster somehow is building pressure and applying plunger pressure to the master cylinder? What about proportioning valve? I'd welcome any advise
Tuned
Joined: May 2006
Posts: 304
Likes: 77
From: St Paul MN
In my experience, grabbing brakes are from air in the lines.
Bleeding without equipment takes two people, some hose, excess container, and a container of new brake fluid.
Work your way around the truck one tire at a time. You know there is air in the line if you open the bleeder and fluid comes out without pushing down the pedal.
I will see if there is a good video on it
Watch out, the fluid eats paint and shouldn't get on your skin
Bleeding without equipment takes two people, some hose, excess container, and a container of new brake fluid.
Work your way around the truck one tire at a time. You know there is air in the line if you open the bleeder and fluid comes out without pushing down the pedal.
I will see if there is a good video on it
Watch out, the fluid eats paint and shouldn't get on your skin
Tuned
Joined: May 2006
Posts: 304
Likes: 77
From: St Paul MN
3:00 to 5:00 gets you the idea
I put a hose on the bleeder so it isnt so messy.
If you pump the brakes a few times, stop, and open the bleeder with no force on the pedal and fluid shoots out there is still air in it.
Sometimes helps to let it sit overnight (air gets stuck in pockets)
good luck
Lead Driver
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Logistics Pro
Joined: Jun 2018
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No it has to do with the master cylinder rod adjustment not releasing. Power brakes or not the rod is not coming back to a reset the master cylinder and holding pressure.
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Thread Starter
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5th Wheeling
Joined: May 2021
Posts: 30
Likes: 10
Thanks for all the input. To address the first response. The new booster is working great. The rod is adjusted correctly and I have good pedal. I feel pretty certain the brakes are bled completely. I guess I'll look at he proportioning valve. I still welcome any input
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