Brakes locking up
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New User
Joined: Jul 2014
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From: San Angelo
Brakes locking up
Hi all, I have a 1981 Ford F100 Custom 2WD. Straight 6. I've replaced my master cylinder recently, and now my brakes are starting to lock up. I bench bled my master cylinder before install, and I bled my lines with a cheap bleeder gun from Auto Zone in the recommended order, furthest from the mc, first etc.. I did notice that the brake fluid was just barely flowing while bleeding. The brakes work for a few miles, then they lock up. After about a day, they're fine again and the whole process starts over. What did I do wrong? Any advice would be greatly appreciated. Thanks for reading.
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Joined: Apr 2011
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From: Orlando area
Is it the front brakes or rear brakes locking? Both wheels or just one wheel?
Could be a sticking caliper or piston, also rear brakes out of adjustment can cause one wheel to lockup faster than the other during hard braking. Problems due to heat from braking is more common in front brakes where it causes piston to stick, then it cools down and works okay for a while. Also, sometimes dirt/debris in the brake system around the caliper piston will cause a problem such as when the pads are replaced as the pistons are pushed back in their bore where the dirt has accumulated. Perhaps you stirred up the debris in the brake system/lines and now its causing the piston to stick in the caliper.
More details please.
Could be a sticking caliper or piston, also rear brakes out of adjustment can cause one wheel to lockup faster than the other during hard braking. Problems due to heat from braking is more common in front brakes where it causes piston to stick, then it cools down and works okay for a while. Also, sometimes dirt/debris in the brake system around the caliper piston will cause a problem such as when the pads are replaced as the pistons are pushed back in their bore where the dirt has accumulated. Perhaps you stirred up the debris in the brake system/lines and now its causing the piston to stick in the caliper.
More details please.
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Joined: Jan 2001
Posts: 56,980
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From: Virginia
The spec below is very important. If the master is being pushed ever so slightly, it will cover up the compensation ports in the bottom of the master and cause the problem you describe.
The push rod should extend past the face of the booster as follows:
1976: 0.880-0.895 in.
1977-81: 0.931-0.946 in.
1982-86: 0.980-0.995 in.
The push rod should extend past the face of the booster as follows:
1976: 0.880-0.895 in.
1977-81: 0.931-0.946 in.
1982-86: 0.980-0.995 in.
Thread Starter
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New User
Joined: Jul 2014
Posts: 23
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From: San Angelo
Is it the front brakes or rear brakes locking? Both wheels or just one wheel?
Could be a sticking caliper or piston, also rear brakes out of adjustment can cause one wheel to lockup faster than the other during hard braking. Problems due to heat from braking is more common in front brakes where it causes piston to stick, then it cools down and works okay for a while. Also, sometimes dirt/debris in the brake system around the caliper piston will cause a problem such as when the pads are replaced as the pistons are pushed back in their bore where the dirt has accumulated. Perhaps you stirred up the debris in the brake system/lines and now its causing the piston to stick in the caliper.
More details please.
Could be a sticking caliper or piston, also rear brakes out of adjustment can cause one wheel to lockup faster than the other during hard braking. Problems due to heat from braking is more common in front brakes where it causes piston to stick, then it cools down and works okay for a while. Also, sometimes dirt/debris in the brake system around the caliper piston will cause a problem such as when the pads are replaced as the pistons are pushed back in their bore where the dirt has accumulated. Perhaps you stirred up the debris in the brake system/lines and now its causing the piston to stick in the caliper.
More details please.
Thread Starter
|
New User
Joined: Jul 2014
Posts: 23
Likes: 2
From: San Angelo
The spec below is very important. If the master is being pushed ever so slightly, it will cover up the compensation ports in the bottom of the master and cause the problem you describe.
The push rod should extend past the face of the booster as follows:
1976: 0.880-0.895 in.
1977-81: 0.931-0.946 in.
1982-86: 0.980-0.995 in.
The push rod should extend past the face of the booster as follows:
1976: 0.880-0.895 in.
1977-81: 0.931-0.946 in.
1982-86: 0.980-0.995 in.
Thread Starter
|
New User
Joined: Jul 2014
Posts: 23
Likes: 2
From: San Angelo
Hi all, I have a 1981 Ford F100 Custom 2WD. Straight 6. I've replaced my master cylinder recently, and now my brakes are starting to lock up. I bench bled my master cylinder before install, and I bled my lines with a cheap bleeder gun from Auto Zone in the recommended order, furthest from the mc, first etc.. I did notice that the brake fluid was just barely flowing while bleeding. The brakes work for a few miles, then they lock up. After about a day, they're fine again and the whole process starts over. What did I do wrong? Any advice would be greatly appreciated. Thanks for reading.
Posting Guru
Joined: Apr 2011
Posts: 1,636
Likes: 5
From: Orlando area
I don't think the moving in reverse but not forward means anything. The gearing in your tranny may be lower in reverse than 1st providing a torque advantage in reverse.
Try this, drive a short distance (5 miles) then immediately jack up the front end. See if the front when spin freely. Try again when cool. Obviously they should be free whether hot or cold.
Also, note that if the rear brakes are not working properly (sticking, out of adjustment, stuck parking brake cable, or faulty proportioning valve) it could make the front brakes seem like they are malfunctioning because you have to apply more brake pedal effort to stop the truck.
I had a similar issue once, where after driving a while the front brakes would drag (actually smoking). It turned out the my calipers (pistons) were sticking. A new set of rebuilt brake calipers fixed the problem.
Try this, drive a short distance (5 miles) then immediately jack up the front end. See if the front when spin freely. Try again when cool. Obviously they should be free whether hot or cold.
Also, note that if the rear brakes are not working properly (sticking, out of adjustment, stuck parking brake cable, or faulty proportioning valve) it could make the front brakes seem like they are malfunctioning because you have to apply more brake pedal effort to stop the truck.
I had a similar issue once, where after driving a while the front brakes would drag (actually smoking). It turned out the my calipers (pistons) were sticking. A new set of rebuilt brake calipers fixed the problem.
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From: Virginia
Along the same theme as my 1st post in this thread, I have a little ranger pickup that I got for free, it had the same problem and had been passed from one person to another, lots of parts replaced, and still the brakes would lock up after it was driven a few miles.
It turned out to be the booster. The booster was rusted and sticking, if you put your foot under the pedal and pulled up on it, it would not do it. Lots of wd40 didn't fix it either, I had to buy a rebuilt booster.
But the cause and the affect were the same. The booster was not releasing totally, slightly pushing on the master, which covered the compensation ports, and when the fluid gets warm it expands and instead of being able to expand into the master cylinder, it starts applying the brakes. Just because that little hole in the bottom of the master is blocked off.
It turned out to be the booster. The booster was rusted and sticking, if you put your foot under the pedal and pulled up on it, it would not do it. Lots of wd40 didn't fix it either, I had to buy a rebuilt booster.
But the cause and the affect were the same. The booster was not releasing totally, slightly pushing on the master, which covered the compensation ports, and when the fluid gets warm it expands and instead of being able to expand into the master cylinder, it starts applying the brakes. Just because that little hole in the bottom of the master is blocked off.
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Joined: Sep 2013
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From: Marlborough, CT
UPDATE: I went home and messed with truck and noticed that once again the front brakes were locking up after a short drive. When I got home and put Ol Blue in reverse, the idle was enough to move him backwards. In drive however the brakes were keeping him from moving until i gave em some gas. Anyone have any ideas?
Thread Starter
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New User
Joined: Jul 2014
Posts: 23
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From: San Angelo
I don't think the moving in reverse but not forward means anything. The gearing in your tranny may be lower in reverse than 1st providing a torque advantage in reverse.
Try this, drive a short distance (5 miles) then immediately jack up the front end. See if the front when spin freely. Try again when cool. Obviously they should be free whether hot or cold.
Also, note that if the rear brakes are not working properly (sticking, out of adjustment, stuck parking brake cable, or faulty proportioning valve) it could make the front brakes seem like they are malfunctioning because you have to apply more brake pedal effort to stop the truck.
I had a similar issue once, where after driving a while the front brakes would drag (actually smoking). It turned out the my calipers (pistons) were sticking. A new set of rebuilt brake calipers fixed the problem.
Try this, drive a short distance (5 miles) then immediately jack up the front end. See if the front when spin freely. Try again when cool. Obviously they should be free whether hot or cold.
Also, note that if the rear brakes are not working properly (sticking, out of adjustment, stuck parking brake cable, or faulty proportioning valve) it could make the front brakes seem like they are malfunctioning because you have to apply more brake pedal effort to stop the truck.
I had a similar issue once, where after driving a while the front brakes would drag (actually smoking). It turned out the my calipers (pistons) were sticking. A new set of rebuilt brake calipers fixed the problem.
Thread Starter
|
New User
Joined: Jul 2014
Posts: 23
Likes: 2
From: San Angelo
Along the same theme as my 1st post in this thread, I have a little ranger pickup that I got for free, it had the same problem and had been passed from one person to another, lots of parts replaced, and still the brakes would lock up after it was driven a few miles.
It turned out to be the booster. The booster was rusted and sticking, if you put your foot under the pedal and pulled up on it, it would not do it. Lots of wd40 didn't fix it either, I had to buy a rebuilt booster.
But the cause and the affect were the same. The booster was not releasing totally, slightly pushing on the master, which covered the compensation ports, and when the fluid gets warm it expands and instead of being able to expand into the master cylinder, it starts applying the brakes. Just because that little hole in the bottom of the master is blocked off.
It turned out to be the booster. The booster was rusted and sticking, if you put your foot under the pedal and pulled up on it, it would not do it. Lots of wd40 didn't fix it either, I had to buy a rebuilt booster.
But the cause and the affect were the same. The booster was not releasing totally, slightly pushing on the master, which covered the compensation ports, and when the fluid gets warm it expands and instead of being able to expand into the master cylinder, it starts applying the brakes. Just because that little hole in the bottom of the master is blocked off.
Thread Starter
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New User
Joined: Jul 2014
Posts: 23
Likes: 2
From: San Angelo
You know what, I didn't adjust it. I didn't have much light to work in when I got home last night that I was trying to see if only 1 tire or both were locked up. This is definitely going to have to be a Sunday morning project. Thanks for the reminder!
Thread Starter
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New User
Joined: Jul 2014
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From: San Angelo
I thought about that as well but I core exchanged the old master cylinder so I no longer have it. I think I'm just going to have to get start from scratch tomorrow and do a few things at a time. What will probably happen is replacement of the whole brake system. I don't want to be driving my kids around and inadvertently put them in danger. Thanks for the idea, I appreciate it.
Posting Guru
Joined: Apr 2011
Posts: 1,636
Likes: 5
From: Orlando area
Along the same theme as my 1st post in this thread, I have a little ranger pickup that I got for free, it had the same problem and had been passed from one person to another, lots of parts replaced, and still the brakes would lock up after it was driven a few miles.
It turned out to be the booster. The booster was rusted and sticking, if you put your foot under the pedal and pulled up on it, it would not do it. Lots of wd40 didn't fix it either, I had to buy a rebuilt booster.
But the cause and the affect were the same. The booster was not releasing totally, slightly pushing on the master, which covered the compensation ports, and when the fluid gets warm it expands and instead of being able to expand into the master cylinder, it starts applying the brakes. Just because that little hole in the bottom of the master is blocked off.
It turned out to be the booster. The booster was rusted and sticking, if you put your foot under the pedal and pulled up on it, it would not do it. Lots of wd40 didn't fix it either, I had to buy a rebuilt booster.
But the cause and the affect were the same. The booster was not releasing totally, slightly pushing on the master, which covered the compensation ports, and when the fluid gets warm it expands and instead of being able to expand into the master cylinder, it starts applying the brakes. Just because that little hole in the bottom of the master is blocked off.