No front brakes! Please help!
06-06-2017, 08:28 AM
#1
Newbie
Thread Starter
Join Date: Jul 2012
Location: Delaware
Posts: 5
Likes: 0
Received 0 Likes
on
0 Posts
Year: 1991
Model: Cherokee
Engine: 4.0
No front brakes! Please help!
I'm hoping this goes here, as I'm dealing with OEM parts.
My 91 originally had the garbage Bendix ABS, which was gutted for a 96 booster/MC/prop valve setup. Worked great until one night I left work and the pedal went to the floor with no braking power. I limped it home and it sat for almost 4 years since I relocated for work and haven't had time to dig into it until now.
First replaced the master cylinder, as I did not see any kind of leak or broken line anywhere. Bench bled it before installing, then while bleeding each wheel, found the FR caliper leaking fluid, so I replaced that. Took it out for a test drive, and while I technically did have brakes, it seemed that only the rears were functioning. If I put even a moderate amount of effort into it, the rears would lock up, and the whole vehicle skids, there's no "nose-dive" feeling of a hard clamping front brake, it just locks up the rear and slides.
i put it back on the lift and took off the FL caliper, and it looked like the rubber seal around the piston had melted, so I replaced that. Drove it again with the EXACT same results.
I have verified that the calipers are mounted on the correct sides with the bleeder above the line, I've even adjusted out the booster rod, thinking that maybe the front brakes just weren't getting enough fluid to clamp down. No dice. Now I'm thinking potentially the proportioning valve is the culprit, but before I go putting out even more money and time to get this thing braking correctly, I wanted to ask for advice here.
Someone please save my sanity!
My 91 originally had the garbage Bendix ABS, which was gutted for a 96 booster/MC/prop valve setup. Worked great until one night I left work and the pedal went to the floor with no braking power. I limped it home and it sat for almost 4 years since I relocated for work and haven't had time to dig into it until now.
First replaced the master cylinder, as I did not see any kind of leak or broken line anywhere. Bench bled it before installing, then while bleeding each wheel, found the FR caliper leaking fluid, so I replaced that. Took it out for a test drive, and while I technically did have brakes, it seemed that only the rears were functioning. If I put even a moderate amount of effort into it, the rears would lock up, and the whole vehicle skids, there's no "nose-dive" feeling of a hard clamping front brake, it just locks up the rear and slides.
i put it back on the lift and took off the FL caliper, and it looked like the rubber seal around the piston had melted, so I replaced that. Drove it again with the EXACT same results.
I have verified that the calipers are mounted on the correct sides with the bleeder above the line, I've even adjusted out the booster rod, thinking that maybe the front brakes just weren't getting enough fluid to clamp down. No dice. Now I'm thinking potentially the proportioning valve is the culprit, but before I go putting out even more money and time to get this thing braking correctly, I wanted to ask for advice here.
Someone please save my sanity!
06-06-2017, 09:35 PM
#3
No, I don't lick fish.
I'm hoping this goes here, as I'm dealing with OEM parts.
My 91 originally had the garbage Bendix ABS, which was gutted for a 96 booster/MC/prop valve setup. Worked great until one night I left work and the pedal went to the floor with no braking power. I limped it home and it sat for almost 4 years since I relocated for work and haven't had time to dig into it until now.
First replaced the master cylinder, as I did not see any kind of leak or broken line anywhere. Bench bled it before installing, then while bleeding each wheel, found the FR caliper leaking fluid, so I replaced that. Took it out for a test drive, and while I technically did have brakes, it seemed that only the rears were functioning. If I put even a moderate amount of effort into it, the rears would lock up, and the whole vehicle skids, there's no "nose-dive" feeling of a hard clamping front brake, it just locks up the rear and slides.
i put it back on the lift and took off the FL caliper, and it looked like the rubber seal around the piston had melted, so I replaced that. Drove it again with the EXACT same results.
I have verified that the calipers are mounted on the correct sides with the bleeder above the line, I've even adjusted out the booster rod, thinking that maybe the front brakes just weren't getting enough fluid to clamp down. No dice. Now I'm thinking potentially the proportioning valve is the culprit, but before I go putting out even more money and time to get this thing braking correctly, I wanted to ask for advice here.
Someone please save my sanity!
My 91 originally had the garbage Bendix ABS, which was gutted for a 96 booster/MC/prop valve setup. Worked great until one night I left work and the pedal went to the floor with no braking power. I limped it home and it sat for almost 4 years since I relocated for work and haven't had time to dig into it until now.
First replaced the master cylinder, as I did not see any kind of leak or broken line anywhere. Bench bled it before installing, then while bleeding each wheel, found the FR caliper leaking fluid, so I replaced that. Took it out for a test drive, and while I technically did have brakes, it seemed that only the rears were functioning. If I put even a moderate amount of effort into it, the rears would lock up, and the whole vehicle skids, there's no "nose-dive" feeling of a hard clamping front brake, it just locks up the rear and slides.
i put it back on the lift and took off the FL caliper, and it looked like the rubber seal around the piston had melted, so I replaced that. Drove it again with the EXACT same results.
I have verified that the calipers are mounted on the correct sides with the bleeder above the line, I've even adjusted out the booster rod, thinking that maybe the front brakes just weren't getting enough fluid to clamp down. No dice. Now I'm thinking potentially the proportioning valve is the culprit, but before I go putting out even more money and time to get this thing braking correctly, I wanted to ask for advice here.
Someone please save my sanity!
06-07-2017, 07:26 AM
#4
Newbie
Thread Starter
Join Date: Jul 2012
Location: Delaware
Posts: 5
Likes: 0
Received 0 Likes
on
0 Posts
Year: 1991
Model: Cherokee
Engine: 4.0
Drums in the rear, and the swap parts I actually bought new from NAPA for a 96 XJ since there was nothing available at my local u-pick.
I think I'm going to pick up a cheap vacuum bleeder to be 100% sure of no air, then if necessary move on to replacing the prop valve. Is a stock replacement my best bet or is it a better idea to go adjustable?
I think I'm going to pick up a cheap vacuum bleeder to be 100% sure of no air, then if necessary move on to replacing the prop valve. Is a stock replacement my best bet or is it a better idea to go adjustable?