hello everyone... i have a mysterious problem with the brakes on my '86 chevy caprice. i've mentioned every detail i can remember about the problem, so sorry for the long length of this post.
a little background: this car is a daily driver during the winter months while my '70 oldsmobile sleeps in the garage until spring. the car has high miles, but runs great, and brakes have always worked fine. i do normal maintainance on this car, but nothing else - it's a driver only, and a good one til now.
alright, it all started one day when the brake pedal seemed to travel a little farther than usual. quickly the problem worsened until the pedal was pushing almost to the floor without as much braking as i would've liked. i checked the fluid reservoir, and it was near empty! i added fluid, and brakes were normal again. simple enough. now, here's where it gets weird...
couldn't find a leak anywhere. i continued to drive the car for a while, and no trouble for a couple of weeks. then it happened again. this time it was worse, and the red brake light came on. i noticed that if i pumped the brakes hard, i could make the light go out. still, couldn't find a trace of a fluid leak anywhere.
inspected the front calipers and hoses, and all looked well. i installed a new set of pads while i was at it. with the new pads, stopping seemed a little better, but fluid still was leaking somewhere. checked all lines, rear drums, and master cylinder. no dice. interestingly, when the fluid would run too low, and the red light would come on - breaking improved a little - although i could tell that the front discs were doing all the work, and the pedal was near the floor all the time. i drove it like this for a short period until i could work on it some more. i was beginning to suspect the master cylinder was bad, possibly leaking, but i couldn't find fluid coming from anywhere.
bought a new master cylinder, did a bench bleed as instructed. the bleeding method was different than in the past. instead of the little clear hoses, i got two threaded plastic plugs. instructions say just depress the cylinder a few times until the bubbles stop forming. ok, done. one thing - one of the plastic plugs was leaking slightly. i didn't know if this was significant, so i decided to put the MC on the car and see what happened.
mounted the MC on the car and the brakes worked! however, the red light was still on, and no matter how many times i pumped, i couldn't get it to go out. still, the brakes worked fine it seemed, yet i noticed a leak coming from the fitting on the MC - the same one that was leaking during the bench bleed! AAAAAAAAAAH!!!!!!
brakes continued to work great for about a day. then i began to notice i had to pump the pedal more and more to stop. 100 miles later, i had no pressure at all. the pedal goes all the way to the floor, but returns very slowly. after three full pumps to the floor, i have SOME braking power. there is still plenty of fluid in the reservoir. when i turn the engine off, i get pressure again, but it creeps slowly to the floor - like the MC was bad.
i'm fearing there's air in the lines, but not sure. how much air causes ZERO pressure? can air go DOWN the lines from the master cylinder? do small leaks bring air into the system? and that red light still won't go out. does that mean there is a problem with the rear drums?
i have only a basic understanding of brake systems. i don't know where to start looking for problems like this. never had this much trouble with brakes before! my next step is to start bleeding the lines, but before i take that step, i thought maybe some of you might have tips or past experiences that could help out. thanks to everyone in advance...
[ March 10, 2003: Message edited by: 98rocket ]
[ March 10, 2003: Message edited by: 98rocket ]
[ March 10, 2003: Message edited by: 98rocket ]
[ March 10, 2003: Message edited by: 98rocket ]
[ March 10, 2003: Message edited by: 98rocket ]
[ March 10, 2003: Message edited by: 98rocket ]
[ March 10, 2003: Message edited by: 98rocket ]
[ March 10, 2003: Message edited by: 98rocket ]</p>
a little background: this car is a daily driver during the winter months while my '70 oldsmobile sleeps in the garage until spring. the car has high miles, but runs great, and brakes have always worked fine. i do normal maintainance on this car, but nothing else - it's a driver only, and a good one til now.
alright, it all started one day when the brake pedal seemed to travel a little farther than usual. quickly the problem worsened until the pedal was pushing almost to the floor without as much braking as i would've liked. i checked the fluid reservoir, and it was near empty! i added fluid, and brakes were normal again. simple enough. now, here's where it gets weird...
couldn't find a leak anywhere. i continued to drive the car for a while, and no trouble for a couple of weeks. then it happened again. this time it was worse, and the red brake light came on. i noticed that if i pumped the brakes hard, i could make the light go out. still, couldn't find a trace of a fluid leak anywhere.
inspected the front calipers and hoses, and all looked well. i installed a new set of pads while i was at it. with the new pads, stopping seemed a little better, but fluid still was leaking somewhere. checked all lines, rear drums, and master cylinder. no dice. interestingly, when the fluid would run too low, and the red light would come on - breaking improved a little - although i could tell that the front discs were doing all the work, and the pedal was near the floor all the time. i drove it like this for a short period until i could work on it some more. i was beginning to suspect the master cylinder was bad, possibly leaking, but i couldn't find fluid coming from anywhere.
bought a new master cylinder, did a bench bleed as instructed. the bleeding method was different than in the past. instead of the little clear hoses, i got two threaded plastic plugs. instructions say just depress the cylinder a few times until the bubbles stop forming. ok, done. one thing - one of the plastic plugs was leaking slightly. i didn't know if this was significant, so i decided to put the MC on the car and see what happened.
mounted the MC on the car and the brakes worked! however, the red light was still on, and no matter how many times i pumped, i couldn't get it to go out. still, the brakes worked fine it seemed, yet i noticed a leak coming from the fitting on the MC - the same one that was leaking during the bench bleed! AAAAAAAAAAH!!!!!!
brakes continued to work great for about a day. then i began to notice i had to pump the pedal more and more to stop. 100 miles later, i had no pressure at all. the pedal goes all the way to the floor, but returns very slowly. after three full pumps to the floor, i have SOME braking power. there is still plenty of fluid in the reservoir. when i turn the engine off, i get pressure again, but it creeps slowly to the floor - like the MC was bad.
i'm fearing there's air in the lines, but not sure. how much air causes ZERO pressure? can air go DOWN the lines from the master cylinder? do small leaks bring air into the system? and that red light still won't go out. does that mean there is a problem with the rear drums?
i have only a basic understanding of brake systems. i don't know where to start looking for problems like this. never had this much trouble with brakes before! my next step is to start bleeding the lines, but before i take that step, i thought maybe some of you might have tips or past experiences that could help out. thanks to everyone in advance...
[ March 10, 2003: Message edited by: 98rocket ]
[ March 10, 2003: Message edited by: 98rocket ]
[ March 10, 2003: Message edited by: 98rocket ]
[ March 10, 2003: Message edited by: 98rocket ]
[ March 10, 2003: Message edited by: 98rocket ]
[ March 10, 2003: Message edited by: 98rocket ]
[ March 10, 2003: Message edited by: 98rocket ]
[ March 10, 2003: Message edited by: 98rocket ]</p>