Tri_X_Troll Posted October 15, 2009 Posted October 15, 2009 Was coming off of the freeway exit ramp and was slowing down as I approached the light and my brake pedal went soft and hit the floor. The brakes will grab real hard when you bottom out the pedal. I checked the brake fluid and it's full. I couldn't see any blown lines anywhere. I'm clueless. :huh???: The pedal used to be kinda firm. It was almost almost as firm as the clutch, but not quite.
Automan2164 Posted October 15, 2009 Posted October 15, 2009 Is it hard like it would be if you had the truck off? Rob L.
Tri_X_Troll Posted October 15, 2009 Author Posted October 15, 2009 No, it just "drops" to the floor and springs up when you take your foot off.
Automan2164 Posted October 15, 2009 Posted October 15, 2009 And no loss of fluid? Essh. Might have had an internal master cylinder failure. Sure the pedal linkage is still connected? Might as well start with the simple stuff... Rob L.
Tri_X_Troll Posted October 15, 2009 Author Posted October 15, 2009 I'm pretty sure the linkage is connected, as they do grab when I bury the pedal to the floor. My brake experience is limited to pads and rotors, so I'm not sure how the linkage goes together, so I'll have to tear into it this weekend.
Tri_X_Troll Posted October 15, 2009 Author Posted October 15, 2009 Pumping the brakes doesn't seem to make any difference and it will hold on the steep hill in front of my house if I hold the pedal to the floor.
HOrnbrod Posted October 15, 2009 Posted October 15, 2009 If the linkage from the booster thru the firewall to the brake pedal is fine and you have no obvious brake fluid leaks, I think your master cylinder has a blown rubber. Now is an excellent time to upgrade to the 95-96 XJ booster/master cylinder.
Oizarod115 Posted October 15, 2009 Posted October 15, 2009 check again for brake fluid leaks, then replace your master cylinder. definitely time for a 95-96 booster upgrade. just completed mine today and the difference is unbelievable.
Eagle Posted October 15, 2009 Posted October 15, 2009 Although it sounds like an internal failure of the master cylinder, if that were the case I would expect that both (a) the brakes would NOT hold on a hill, and (B) it would not have happened suddenly. It sounds more like a ruptured line to the rear wheels. When that happens, the pedal still provides braking by the front wheels, but the pedal drops almost to the floor. If possible, jack up the rear axle (put it on jackstands if you have them), then run it in 2WD up to maybe 10 or 15 MPH and slam on the brakes. See if the rear wheels stop spinning.
Tri_X_Troll Posted October 15, 2009 Author Posted October 15, 2009 I got to thinking. When I pop the cover on the master cylinder, should both sides be full of fluid? One side is full and the other is just damp?
Automan2164 Posted October 15, 2009 Posted October 15, 2009 If that be the case... Your leaking. One res is for front, one for rear. Fill the empty res, and start pumping, you will find your problem REAL quick. ;) Rob L.
HOrnbrod Posted October 15, 2009 Posted October 15, 2009 I got to thinking. When I pop the cover on the master cylinder, should both sides be full of fluid? One side is full and the other is just damp? AAAAARG! I ASSumed the master fluid levels had been checked already. Note to self: DO NOT ASSUME ANYTHING! :doh:
jbhill Posted October 15, 2009 Posted October 15, 2009 sounds like blown wheel cylinder. replace em both and bleed the brakes, you may have not killed the MC.
Automan2164 Posted October 15, 2009 Posted October 15, 2009 I got to thinking. When I pop the cover on the master cylinder, should both sides be full of fluid? One side is full and the other is just damp? AAAAARG! I ASSumed the master fluid levels had been checked already. Note to self: DO NOT ASSUME ANYTHING! :doh: Don, just an oversight... He did say he checked it... Don't beat yerself up. I checked the brake fluid and it's full. I couldn't see any blown lines anywhere. I'm clueless. :huh???: The pedal used to be kinda firm. It was almost almost as firm as the clutch, but not quite. I think he's got it now... Rob L.
Eagle Posted October 15, 2009 Posted October 15, 2009 I got to thinking. When I pop the cover on the master cylinder, should both sides be full of fluid? One side is full and the other is just damp? The big chamber feeds the front brakes, the little chamber feeds the back brakes. Let me guess -- the little chamber is the one that's empty, right? Look for a popped hard line across the rear axle, or somewhere in the area where the lines run along the frame next to the gas tank.
Eagle Posted October 15, 2009 Posted October 15, 2009 I got to thinking. When I pop the cover on the master cylinder, should both sides be full of fluid? One side is full and the other is just damp? AAAAARG! I ASSumed the master fluid levels had been checked already. Note to self: DO NOT ASSUME ANYTHING! :doh: It had been. He reported that it was full. He didn't understand that the two chambers are for different ends of the truck. I checked the brake fluid and it's full.
Automan2164 Posted October 15, 2009 Posted October 15, 2009 I got to thinking. When I pop the cover on the master cylinder, should both sides be full of fluid? One side is full and the other is just damp? AAAAARG! I ASSumed the master fluid levels had been checked already. Note to self: DO NOT ASSUME ANYTHING! :doh: Don, just an oversight... He did say he checked it... Don't beat yerself up. I checked the brake fluid and it's full. I couldn't see any blown lines anywhere. I'm clueless. :huh???: The pedal used to be kinda firm. It was almost almost as firm as the clutch, but not quite. I think he's got it now... Rob L. No love for me Don? :dunno: Rob L. :D
Tri_X_Troll Posted October 15, 2009 Author Posted October 15, 2009 Yep. Little chamber was empty. Found a broken line just about where the lines go by the gas tank, that I couldn't see in the dark. Looks to be the only line that a po didn't replace, all of the others look new. While I'm at it, does anyone have any info on the proportioning valve bypass? Like a good writeup?
Eagle Posted October 15, 2009 Posted October 15, 2009 The two outlets on the front metering block (that thingie just below the master cylinder) that go to the rear are to forward two. The one that comes out the "nose" is the one you keep. The one out the forward bottom is the bypass, and that gets blocked off. Go to a good hardware store and buy a 5/8 SAE (fine thread) bolt. The shortest available is 1" -- cut it off to about 3/8" long, put an O-ring around it, put a dab of RTV on the end, and screw it into that front/bottom outlet. Run ONE new line from the "nose" outlet in front directly to the flex hose at the rear axle. Done.
maddzz1 Posted October 16, 2009 Posted October 16, 2009 THE ultimate prop valve replacement thread (I bookmarked it last time after a day of searching): viewtopic.php?t=4968&highlight=prop+valve
Tri_X_Troll Posted October 25, 2009 Author Posted October 25, 2009 The two outlets on the front metering block (that thingie just below the master cylinder) that go to the rear are to forward two. The one that comes out the "nose" is the one you keep. The one out the forward bottom is the bypass, and that gets blocked off. Go to a good hardware store and buy a 5/8 SAE (fine thread) bolt. The shortest available is 1" -- cut it off to about 3/8" long, put an O-ring around it, put a dab of RTV on the end, and screw it into that front/bottom outlet. Run ONE new line from the "nose" outlet in front directly to the flex hose at the rear axle. Done. Got it all put back together, and running the new line from the block was a big pita. At least the stupid valve is gone. O'Reilleys actually had a threaded plug that fit perfectly into the block. I didn't do an o-ring or any rtv, maybe I should have. I just opened the package and threaded the brass plug in.
Eagle Posted October 25, 2009 Posted October 25, 2009 O'Reilleys actually had a threaded plug that fit perfectly into the block. I didn't do an o-ring or any rtv, maybe I should have. I just opened the package and threaded the brass plug in. You should be good. Under normal conditions there's nothing coming out that port anyway, so no pressure that might force fluid around the threads of a dry plug.
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