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Hot Rod Forum : Hotrodders Bulletin Board > Tech Help> Suspension - Brakes - Steering> Brakes appling themselves Help
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Topic Review (Newest First)
09-23-2012 08:32 PM
65G10 Mine will "pump" up tight also , but I know I have the rod between the pedal and MC adjusted super close. I can get it to release fully with a toe pull on the pedal,No Booster on mine. Usually going a small distance down the road will allow the normal knock back from the rotors against the pads to release things. . Are you using an aftermarket below the floor setup or thru the firewall ? Sometimes these 4 wheel conversions get a little glitchy. Have you put it up on stands to see if it is effecting both front and rear or just one end ? The Master cylinder has to fully comeback to release. if pulling it back releases the brakes then it has to be in the linkage or MC and even a slight failure to return will create the pump up . Maybe some pics of the pedal to Booster setup would help.
09-23-2012 08:09 PM
Stude57
Quote:
Originally Posted by 68NovaSS View Post
Doesn't make sense it will release when you pull the pedal up by hand but not when it's pulled up with a spring.
Apparently the spring is not strong enough to pull the pedal back. The spring is strong enough that when I put it on I needed vise grips to pull it back to its bracket. I read in another thread about a simular problem and a poster suggested that brake fluid may be leaking past a seal in the m/c, so I may change the m/c in the next few days. I was trying to determine the reason before just replacing parts.
09-23-2012 07:48 PM
S10 Racer
Quote:
Originally Posted by 68NovaSS View Post
Doesn't make sense it will release when you pull the pedal up by hand but not when it's pulled up with a spring.
X2
09-23-2012 06:39 PM
68NovaSS Doesn't make sense it will release when you pull the pedal up by hand but not when it's pulled up with a spring.
09-23-2012 05:31 PM
Stude57
Quote:
Originally Posted by S10 Racer View Post
I'm just using logic in that the issue did not start until you replaced the booster. Just because it's new, don't mean it's good. You never know how long that new booster set on a shelf somewhere. If it checked out and you're satisfied it's not the booster, then there is a problem elsewhere of course.
I agree that just because a part is new doesn't mean it can't be defective. I did the 3 tests in the link posted by RWENUT in this thread and the booster passed. I also verfied the check valve works and I have over 20in of vacuum. I'm just trying to avoid throwing parts at the problem.
I have now learned I can duplicate the problem at will. I start the truck and put in in gear. I keep tapping the brakes to keep the truck from moving and on about the 5th brake application they fail to release and I can tell that with each brake application from the beginning the brakes release less and less. After they fail to release I just pull up on the pedal and the truck starts to move.
09-23-2012 05:24 PM
Stude57
Quote:
Originally Posted by enjenjo View Post
I believe the booster pushrod to the master cylinder is out of adjustment, or the pushrod from the pedal to the booster is out of adjustment, IE. too long in both cases.
I put a dab of grease on the end of the booster pushrod and bolted the m/c tight and kept doing this until I didn't transfer any grease and then turned the pushrod in one turn. I'm not sure how to adjust the pedal to booster pushrod.
09-23-2012 05:21 PM
Stude57
Quote:
Originally Posted by 65G10 View Post
Are you running residual valves ? If the MC resevoir is higher than the calipers by quite a bit it can prevent them from releasing correctly. Combine this with a small amount of heat build up it can cause intermittent braking pressure. I cannot remember the particulars , but I know of at least one case where a NEW booster was at fault. Is the pedal to booster connection allowing a complete return? Just ideas.
No residual valves. I followed the booster check in a link provided by RWENUTS and all test show the booster to be good. I can get the system to fail to release the brakes in the garage so I don't think heat is the problem. I start with 1/4 to 1/2 inch freeplay. Start the truck and put it in gear and start applying the brakes to hold the truck. After about the 5th brake application the brakes fail to release. I just pull up on the pedal and they release.
09-23-2012 04:04 PM
enjenjo I believe the booster pushrod to the master cylinder is out of adjustment, or the pushrod from the pedal to the booster is out of adjustment, IE. too long in both cases.
09-23-2012 12:24 PM
T-bucket23
Quote:
Originally Posted by S10 Racer View Post
I'm just using logic in that the issue did not start until you replaced the booster. Just because it's new, don't mean it's good. You never know how long that new booster set on a shelf somewhere. If it checked out and you're satisfied it's not the booster, then there is a problem elsewhere of course.
This is also my vote.
09-23-2012 10:31 AM
S10 Racer
Quote:
Originally Posted by Stude57 View Post
New booster. Why do you think it's the booster other than it being replaced? I did the booster tests shown on a link in this post and it checked out
I'm just using logic in that the issue did not start until you replaced the booster. Just because it's new, don't mean it's good. You never know how long that new booster set on a shelf somewhere. If it checked out and you're satisfied it's not the booster, then there is a problem elsewhere of course.
09-23-2012 10:31 AM
65G10 Are you running residual valves ? If the MC resevoir is higher than the calipers by quite a bit it can prevent them from releasing correctly. Combine this with a small amount of heat build up it can cause intermittent braking pressure. I cannot remember the particulars , but I know of at least one case where a NEW booster was at fault. Is the pedal to booster connection allowing a complete return? Just ideas.
09-23-2012 09:40 AM
Stude57 New booster. Why do you think it's the booster other than it being replaced? I did the booster tests shown on a link in this post and it checked out
09-23-2012 09:06 AM
timothale
heat build up ?

My son had a nash Metro that we swapped in a 1600 pinto and 4 spd, the brake lines were too close to the exhaust, boil the fluid ,
09-23-2012 09:02 AM
S10 Racer Sounds like a defective booster since the problem started after replacing it. Was the booster new or used?
09-23-2012 08:52 AM
RWENUTS Maybe something here.
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