No front brakes!

My rig is a 91/4.0/4wd that originally had the nightmare Bendix ABS, but it's been swapped for a 96 MC/booster. Everything was great until I got off work one night and the pedal went to the floor. Limped it home where it sat for nearly 4 years since I relocated for work. Never saw any leaks, never saw any broken lines. Now I'm trying to get it back on the road.

First replaced the MC (after bench bleeding it), then while bleeding each brake found the FR caliper leaking fluid when the pedal was pressed. Replaced that and re-bled, and while it seemed like everything was fine, I test drove it and it seemed that only the rear brakes were grabbing. When I try to come to a quick stop, the rears just lock up and it skids, like the front isn't grabbing whatsoever. Took off the FL caliper and the rubber around the piston looked like it had melted, so I replaced that, same exact results. I've researched the issue and read that sometimes calipers mounted on incorrect sides is the issue, but verified mine are oriented correctly.

I am at a complete loss, unless they just need to be bled even more, but I've gone through quite a bit of fluid. Is there something I'm missing here? I was going to try gravity bleeding everything next but wanted to ask here.

Sorry for the long post, this is driving me crazy! Thanks!


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The calipers are side specific. If they installed correctly the bleeder is at the top of the caliper...if not the bleeders will be at the bottom. If so, you'll never get the air out...because air bubbles go UP in liquid. HTH

Volatile said:

I've researched the issue and read that sometimes calipers mounted on incorrect sides is the issue, but verified mine are oriented correctly.

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ParadiseXJ said:

The calipers are side specific. If they installed correctly the bleeder is at the top of the caliper...if not the bleeders will be at the bottom. If so, you'll never get the air out...because air bubbles go UP in liquid. HTH

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He stated that he already verified they calipers are oriented correctly. I would look at the lines themselves, hard and soft, and the condition they are in. Are they original, or new? Hard lines can get a blockage, and soft lines can collapse internally. How was the fluid flowing while bleeding? Also check your knuckles to see if there is a groove the caliper has made, and keeping the pads from engaging.

If the system ran dry you may have collapsed the proportioning valve when you tried to bleed the brakes.

If it sat for 4 yrs chances are good tjat the whole system needs to be flushed and bled. Brake fluid likes absorbing moisture.

RCP Phx said:

If the system ran dry you may have collapsed the proportioning valve when you tried to bleed the brakes.

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X2 Even if it didn't run dry, if the pedal dropped to the floor, the differences in pressure between the two channels can cause this.

Drums on the back still? I'd pull them off and take a look. They might be all Rusty and just grabbing too soon, especially if it sat that long. I wouldn't be surprised if the front pads need to reseat as well to work properly.

So a little update and some more info, I'm still in the same boat.

I took the advice from CarbonXJ and inspected the knuckles, and there was definitey a groove worn in. I cleaned them up on both sides to bare metal so I've hopefully eliminated that as the potential issue. Thanks for mentioning this, i'm sure it was influencing the pad's engagement and had no idea it was an issue.

The soft lines are original, and the flow of fluid is fine. I bought a Motive power bleeder and bled all four wheels again, confirming that there was no air in the system, and also that lines are flowing as they should. Side note, I don't know how I bled brakes without one of those power bleeders, they're awesome.

Test drove it again, and have the exact same symptoms of it locking in the rear and barely engaging in the front. I put it back on the lift and popped the front wheels off, and when the brake is pressed the calipers are technically engaging, just not nearly to the degree they need to be. The only things I haven't done are pull and inspect the drums or replace the proportioning valve. My question about the valve though is wouldn't I see reduced fluid when bleeding if it was stuck?

Also, is there any chance that the booster rod needs to be adjusted since the master was replaced and not the booster? I've googled boosters without the master attached and comparatively mine looks recessed much further into the booster, the end of the rod barely sticking out past the edge of the opening.

Thanks again!