Brake problems
Thread Starter
|
New User
Joined: Apr 2020
Posts: 13
Likes: 0
From: Cheney, WA
Brake problems
I have a 1977 F150 4x4 shortbed, and after going through numerous brand new master cylinders that were all defective before even putting them on the truck, I installed a brake master cylinder off a 1990 F150. Currently my brakes are super soft when i start driving but after about ten minutes of driving the pedal becomes rock hard and the front calipers dont release. I have a hard time getting the truck above 45, and if maintaining a constant pressure of the gas pedal you can feel the truck start to gradually slow down as the brakes lock up tighter and tighter. I'm at a loss. The system has new fluid all the way through it and ive adjusted the pedal from the booster into the master cylinder countless times. I've replaced both front calipers, And forums on hear said the 90 master cylinder would work with my truck. Does anyone know what could be causing this issue?
Postmaster
Joined: Nov 2009
Posts: 3,189
Likes: 0
From: SE Georgia
I have a 1977 F150 4x4 shortbed, and after going through numerous brand new master cylinders that were all defective before even putting them on the truck, I installed a brake master cylinder off a 1990 F150. Currently my brakes are super soft when i start driving but after about ten minutes of driving the pedal becomes rock hard and the front calipers dont release. I have a hard time getting the truck above 45, and if maintaining a constant pressure of the gas pedal you can feel the truck start to gradually slow down as the brakes lock up tighter and tighter. I'm at a loss. The system has new fluid all the way through it and ive adjusted the pedal from the booster into the master cylinder countless times. I've replaced both front calipers, And forums on hear said the 90 master cylinder would work with my truck. Does anyone know what could be causing this issue?
Thread Starter
|
New User
Joined: Apr 2020
Posts: 13
Likes: 0
From: Cheney, WA
Lead Driver
Joined: Oct 2018
Posts: 7,894
Likes: 2,372
Are you sure the masters you' had were for disk brakes ? drum brakes have a residual valve in the master you don't want on discs. though it still should release.
Have you tried unhooking and plugging the booster ? don't go flying down the freeway but try the brakes without the booster hooked up at slow speeds to see if they still lock.
You said you have adjusted the rod between the master and booster. how are you adjusting it and are you positive it's correct ? this would cause your problem.
I have heard of brake hoses going bad and working like a check valve . I've never seen it and it sounds far fetched to me but when you have a strange problem consider anything.
The distribution valve is a possibility , though I've never seen it cause your problem.
Have you tried unhooking and plugging the booster ? don't go flying down the freeway but try the brakes without the booster hooked up at slow speeds to see if they still lock.
You said you have adjusted the rod between the master and booster. how are you adjusting it and are you positive it's correct ? this would cause your problem.
I have heard of brake hoses going bad and working like a check valve . I've never seen it and it sounds far fetched to me but when you have a strange problem consider anything.
The distribution valve is a possibility , though I've never seen it cause your problem.
Thread Starter
|
New User
Joined: Apr 2020
Posts: 13
Likes: 0
From: Cheney, WA
Are you sure the masters you' had were for disk brakes ? drum brakes have a residual valve in the master you don't want on discs. though it still should release.
Have you tried unhooking and plugging the booster ? don't go flying down the freeway but try the brakes without the booster hooked up at slow speeds to see if they still lock.
You said you have adjusted the rod between the master and booster. how are you adjusting it and are you positive it's correct ? this would cause your problem.
I have heard of brake hoses going bad and working like a check valve . I've never seen it and it sounds far fetched to me but when you have a strange problem consider anything.
The distribution valve is a possibility , though I've never seen it cause your problem.
Have you tried unhooking and plugging the booster ? don't go flying down the freeway but try the brakes without the booster hooked up at slow speeds to see if they still lock.
You said you have adjusted the rod between the master and booster. how are you adjusting it and are you positive it's correct ? this would cause your problem.
I have heard of brake hoses going bad and working like a check valve . I've never seen it and it sounds far fetched to me but when you have a strange problem consider anything.
The distribution valve is a possibility , though I've never seen it cause your problem.
Postmaster
Joined: Nov 2009
Posts: 3,189
Likes: 0
From: SE Georgia
You could possibly have a collasped brake hose as mentioned. I would put a stock master cylinder back on.
Trending Topics
Thread Starter
|
New User
Joined: Apr 2020
Posts: 13
Likes: 0
From: Cheney, WA
Are you sure the masters you' had were for disk brakes ? drum brakes have a residual valve in the master you don't want on discs. though it still should release.
Have you tried unhooking and plugging the booster ? don't go flying down the freeway but try the brakes without the booster hooked up at slow speeds to see if they still lock.
You said you have adjusted the rod between the master and booster. how are you adjusting it and are you positive it's correct ? this would cause your problem.
I have heard of brake hoses going bad and working like a check valve . I've never seen it and it sounds far fetched to me but when you have a strange problem consider anything.
The distribution valve is a possibility , though I've never seen it cause your problem.
Have you tried unhooking and plugging the booster ? don't go flying down the freeway but try the brakes without the booster hooked up at slow speeds to see if they still lock.
You said you have adjusted the rod between the master and booster. how are you adjusting it and are you positive it's correct ? this would cause your problem.
I have heard of brake hoses going bad and working like a check valve . I've never seen it and it sounds far fetched to me but when you have a strange problem consider anything.
The distribution valve is a possibility , though I've never seen it cause your problem.
FTE Stories
Ford Trucks for Ford Truck Enthusiasts
3 Best / 3 Worst Parts of Modern Ford Ownership
Brett Foote
10 Amazing Upgrades That Solve Common Ford Truck Owner Headaches
Pouria Savadkouei
Every 2026 Ford Engine Explained
Brett Foote
10 Ugly Ford Trucks That We Still Kinda Love
Joe Kucinski
10 Things Every Truck Owner NEEDS (2026 Edition)
Michael S. Palmer
Rezvani's Latest Post-Apocalyptic Monster Is a Ford F-150 Raptor Underneath
Verdad Gallardo
Top 10 Most Expensive Ford Trucks Ever Sold on Bring a Trailer
Joe Kucinski
2027 Ford Super Duty Buyer's Guide (Every Model, Engine, & Package)
Brett Foote
Top 10 Ford Truck Tragedies
Joe Kucinski
Thread Starter
|
New User
Joined: Apr 2020
Posts: 13
Likes: 0
From: Cheney, WA
The only stock master cylinder I have is the one I took off the truck, which also had a really spongy pedal and we couldnt get it to bleed. Constant air in the lines.
Lead Driver
Joined: Oct 2018
Posts: 7,894
Likes: 2,372
While possible the hoses are probably the least likely cause.
The rod on the booster should be adjusted to just make contact with the master cylinder piston. being slightly short is okay. it won't effect your pedal really, but it has a huge effect on your brakes if it's incorrect. you really need the correct master they're pretty specific.
I suspect your booster is the problem if the master or the rod adjustment isn't. unhooking it may tell you what you need to know but it may not. if it's an adjustment or binding issue from stuck or damaged component it may still hold the master in. but when you say it pulls the brakes on that makes me think booster, the booster and your foot are the only things in the system that apply force to activate the brakes.
The rod on the booster should be adjusted to just make contact with the master cylinder piston. being slightly short is okay. it won't effect your pedal really, but it has a huge effect on your brakes if it's incorrect. you really need the correct master they're pretty specific.
I suspect your booster is the problem if the master or the rod adjustment isn't. unhooking it may tell you what you need to know but it may not. if it's an adjustment or binding issue from stuck or damaged component it may still hold the master in. but when you say it pulls the brakes on that makes me think booster, the booster and your foot are the only things in the system that apply force to activate the brakes.
Thread Starter
|
New User
Joined: Apr 2020
Posts: 13
Likes: 0
From: Cheney, WA
While possible the hoses are probably the least likely cause.
The rod on the booster should be adjusted to just make contact with the master cylinder piston. being slightly short is okay. it won't effect your pedal really, but it has a huge effect on your brakes if it's incorrect. you really need the correct master they're pretty specific.
I suspect your booster is the problem if the master or the rod adjustment isn't. unhooking it may tell you what you need to know but it may not. if it's an adjustment or binding issue from stuck or damaged component it may still hold the master in. but when you say it pulls the brakes on that makes me think booster, the booster and your foot are the only things in the system that apply force to activate the brakes.
The rod on the booster should be adjusted to just make contact with the master cylinder piston. being slightly short is okay. it won't effect your pedal really, but it has a huge effect on your brakes if it's incorrect. you really need the correct master they're pretty specific.
I suspect your booster is the problem if the master or the rod adjustment isn't. unhooking it may tell you what you need to know but it may not. if it's an adjustment or binding issue from stuck or damaged component it may still hold the master in. but when you say it pulls the brakes on that makes me think booster, the booster and your foot are the only things in the system that apply force to activate the brakes.
Lead Driver
Joined: Oct 2018
Posts: 7,894
Likes: 2,372
you should be able to tell if it's the booster before you replace it. not that replacing it would be a bad idea anyway. but getting the correct master would be the first thing I'd buy assuming the booster isn't the problem.
Sounds like you have it adjusted properly.
Sounds like you have it adjusted properly.
Trailering
Joined: Apr 2019
Posts: 16
Likes: 1
From: San jauns islands
bad break's
I had basically the same problem. Replaced master cylinder pads rotors. Start driving and if I had to use the brakes frequently the rotors would get hot and cause problems. So I replaced the soft lines problem solved, the old soft lines swell when the brake fluid gets hot.