RAB problem, Bleeding??

Hello. Im a new member, so if this has been covered somewhere else, just direct me please.

Intro: I got a ‘92 Explorer XLT from a friend who was leaving the country permanently. He wants me sell it for him but it has some problems to fix. I don’t have much experience driving this car but Im pretty sure the brake pedal should not go nearly to the floor. I noticed at some point the RABS light was on and the parking brake light as well (probably not related). I checked the brake fluid reservoir and it was empty. I filled it and pumped the brake and it was empty again. I looked under the car and found a big puddle which leads me to a brake line that pees brake fluid.

I replaced the line. Its funny how I can sum up all that work in four words.

My double-flares are of the highest quality and there are no leaks in the line. By the way, why does ford have two different size fittings on one piece of brake line. Its ridiculous! They have a 3/16" line with a 3/16" flare nut on one end and a 1/4" flare nut on the other. What is up with that. Anyway, back to the problem.

I bled the brakes in the correct order according to Haynes. RR, LR, RF, and LF. The problem is my brake pedal still goes to the floor and the ABS light is still on. I assume I have gotten air in many parts of the system since all the fluid ran out of the brake line. How do I bleed the air out? Do I need to pressure bleed it? Do I need some special tool to open the ABS solenoids to help bleeding? Am I going to have to spend three hundred dollars at the dealer to get fresh brake fluid? Should I just keep bleeding and bleeding the brakes and eventually the air will come out?

the RABS system you have requires no special treatment. bleed it like it isn't even there.

Bleed into a jar or bottle, then, if needed, strain and re-use fluid after the air bubbles disapate.

Buymycar said:

...I noticed at some point the RABS light was on and the parking brake light as well (probably not related). I checked the brake fluid reservoir and it was empty.
...why does ford have two different size fittings on one piece of brake line. Its ridiculous! They have a 3/16" line with a 3/16" flare nut on one end and a 1/4" flare nut on the other. What is up with that.

I bled the brakes in the correct order according to Haynes. RR, LR, RF, and LF. The problem is my brake pedal still goes to the floor and the ABS light is still on. I assume I have gotten air in many parts of the system since all the fluid ran out of the brake line. How do I bleed the air out? Do I need to pressure bleed it? Do I need some special tool to open the ABS solenoids to help bleeding? Am I going to have to spend three hundred dollars at the dealer to get fresh brake fluid? Should I just keep bleeding and bleeding the brakes and eventually the air will come out?

Click to expand...

Some answers.
The Red brake warning light only comes on for 2 reasons (either the E-brake is on or the fluid in the MC is low {sensor located on the MC})

Different brake line fittings.. Basically certain parts of the brake system (RABS and HCU) were Bosch metric components added to the std system (optional upgrade at the time I guess). These components required metric fittings so that is why certain lines have std on one end and metric on the other. Which line(s) did you replace? BTW Although they look similar metric fittings require bubble flares not double flares for std.

Bench bleeding is the fastest way to get air out of the MC... otherwise you could bleed all day and not achieve a solid pedal...

The scan tool (or similar device) would be needed to bleed 4WABS as the front solenoids in the HCU would need to be cycled to help expel any trapped air.

The line I replaced runs from a hydraulic block over the front axle (proportioning valve?) all the way back along the left frame rail, behind the gas tank, and then connects to a rubber line near the rear axle. The end of the line at the block was 1/4". The 1/4" adapter i put fit perfectly, there is no way I was cutting new threads. Im sure it was 1/4" on one end and 3/16" on the other.

As far as I can tell, there is no sensor on the MC. Its just a bare piece of steel with two brake lines and a bare plastic reservior on top.

I tried bleeding again from the wheels to no avail. I asked at Advance Auto about "bench bleeding" and the guy seemed to know what I was talking about, but did not know of any kit or tool. Apparently you can bench bleed by just sticking your fingers in the ports on the MC to keep it from sucking in air. I may try this with it on the vehicle.

Heres something you guys can answer. Do you beed with the engine running or stopped. When the engine is off, I get a rock hard peddle. When the engine is running is very soft and goes to the floor.

1) Always bleed with the engine off.. the increased pressure can damage the MC seals and bottom out the piston(s)..
2) The bench bleed kits contains various plugs to block off the ports so you don't have to use your fingers and they make a complete seal.
3) I replaced the hardline from the HCU in the engine bay to the rear brake hose block as you did. (had to drop the gas tank to remove the old line and plumb the new).. On my '93 the line was all 3/16"...Your mix of 3/16 and 1/4 is slightly strange (if the parts ore original), but not unheard of.

touche'

1. OK, so I wont bleed with the engine on. Thats bad.

2. I found a bench bleed kit online for 7 bucks. Looks pretty crappy. After bleeding the MC, I still have to bleed the lines I imagine. Pulling the lines off the MC will cause air to get in the system.

3. I dont think I have an HCU on the '92. Its only RABs so I think its a proportioning valve up front or some other hydraulic contraption. It was definately OG tubing with the factory metal loom over it. Yes, dropping the gas tank made the job much more fun. Impact wrenchs and dirt in my hair are great.

Thanks for the help. I'll keep you posted.

If you don't know the history of the truck, it may also be worth looking at the rear wheel cylinders. If those boots leak, it'll never bleed right.

Partial Resolution

Thanks for the tips everyone.

So apparently there was air in the master cylinder that is extremely difficult to get rid of. The pedal feel came back after extensive bench bleeding. What a pain in the ass.

Im still unsure how to resolve the RABs light and parking brake light on the dash. I don't want to pay $60 just for someone to connect to a computer and read off which sensor is bad. Do I have any other options?

Problem Solved

Just thought I would give this thread some closure. I got the parking brake and RABs warning lights to turn off by replacing the "wheel speed sensor" located in the rear differential. I was told this sensor fails most often and was the most likely problem with my RABs system. They only cost $26, so I used the guess and check method of repair and I got lucky.

Just to pull the trouble code from the RABs computer would have been $60 at the brake shop. Im glad I avoided that waste.

Thanks for the help yall.