- Joined
- Aug 7, 2007
- Messages
- 508
- Reaction score
- 1
- Points
- 0
- Location
- California central coast
- Vehicle Year
- 1991
- Vehicle
- Ford
- Engine Size
- 4.0L
Well, I'm more than a bit annoyed at myself for not noticing this A LOT earlier, but I don't have functional rear brakes in the '91 Exploder. In fact, I suspect they have been inoperative at least since I bought the vehicle over 3 years ago. The parking brake works just fine; I insist it hold the vehicle on the steepest part of my driveway, over 30% grade (I believe this rules out all the mechanicals, and requires a hydraulic solution).
I noticed the front brakes could be more easily locked up than I'd like, but I attributed it to the much heavier GVWR compared to the Bronco II I'd previously had. Wrong; it's that the front brakes are providing 100% of the stopping power.
I figured it out when I replaced a sticky caliper, and decided to flush the brakes since I had a bunch of brake fluid around and I hadn't done it before. I had no idea if the previous owner had ever done it (though I think I know the answer now). Opening both rear brake bleeders and having my wife stand on the brake pedal (with the parking brake off) yielded absolutely nothing. I completely removed the bleed screws and discovered they were full of rust. Still nothing. I cracked the fitting on the left right rear wheel cylinder (the left is a bit bent up, though it doesn't appear crimped, and I can't get a flare nut wrench around it because of that).
The master cylinder appears fine; with the pedal down, cracking both fittings yields some fluid.
The rear union fittings are accessible behind the spare tire, but appear to be rusted solid. Same for the rear soft-line connector. I can't easily get at the RABS valve without disassembling several parts in the way. Obviously, these will have to change, but before I go there, I want a stupidity check. Please verify my assumptions:
1. The problem is a hydraulic blockage somewhere between the master cylinder and junction atop the rear end.
2. RABS won't cause this problem without setting a DTC (the RABS self test does run).
3. Nonfunctional (disabled) RABS will have the opposite failure mode -- it will never disengage the rear brakes.
4. There aren't any mechanical (inside brake drums) problems that can cause this behavior.
Note that the rear brake line appears to be EMPTY. Not full of rust. And the pedal feel is quite firm.
I'm debating throwing parts at it (replacing the rear brakes including wheel cylinders and drums) because they are probably original and I know the rear wheel cylinders are full of rust. I doubt this would solve the problem, but I think it needs to be done anyway.
Now I'm much relieved I couldn't find the time for that drive up Pike's Peak I almost did two weeks ago....
I noticed the front brakes could be more easily locked up than I'd like, but I attributed it to the much heavier GVWR compared to the Bronco II I'd previously had. Wrong; it's that the front brakes are providing 100% of the stopping power.
I figured it out when I replaced a sticky caliper, and decided to flush the brakes since I had a bunch of brake fluid around and I hadn't done it before. I had no idea if the previous owner had ever done it (though I think I know the answer now). Opening both rear brake bleeders and having my wife stand on the brake pedal (with the parking brake off) yielded absolutely nothing. I completely removed the bleed screws and discovered they were full of rust. Still nothing. I cracked the fitting on the left right rear wheel cylinder (the left is a bit bent up, though it doesn't appear crimped, and I can't get a flare nut wrench around it because of that).
The master cylinder appears fine; with the pedal down, cracking both fittings yields some fluid.
The rear union fittings are accessible behind the spare tire, but appear to be rusted solid. Same for the rear soft-line connector. I can't easily get at the RABS valve without disassembling several parts in the way. Obviously, these will have to change, but before I go there, I want a stupidity check. Please verify my assumptions:
1. The problem is a hydraulic blockage somewhere between the master cylinder and junction atop the rear end.
2. RABS won't cause this problem without setting a DTC (the RABS self test does run).
3. Nonfunctional (disabled) RABS will have the opposite failure mode -- it will never disengage the rear brakes.
4. There aren't any mechanical (inside brake drums) problems that can cause this behavior.
Note that the rear brake line appears to be EMPTY. Not full of rust. And the pedal feel is quite firm.
I'm debating throwing parts at it (replacing the rear brakes including wheel cylinders and drums) because they are probably original and I know the rear wheel cylinders are full of rust. I doubt this would solve the problem, but I think it needs to be done anyway.
Now I'm much relieved I couldn't find the time for that drive up Pike's Peak I almost did two weeks ago....