Rabs Valve

[icanfixall]

What is the procedure for bleeding the Rabs valve?

 

[crash-harris]

I use a vacuum bleeder. If it has air in the dump valve, IIRC you have to disconect the harness and apply power to one of the pins to get the valve to open. I had a link once, probably gone by now, but I'll double check my red Haynes manual.

 

[OLDBULL8]

After bleeding the rear brakes, bleed the RABS valve, same as you would bleed the brakes.

Why do you need to bleed the RABS?

 

[Black dawg]

With the lid off of the master, just open the screw and let it gravity bled. I dont know how many of these I have replaced, but this has always worked for me.

 

[gandalf]

The RABS on my truck has a bleed fitting, just like each of the wheel cylinders. I bleed it just like I would a wheel cylinder. If there is a better way I'd certainly like to know.

My feeling is that if somebody put a bleed fitting there, they must think the RABS needs bleeding.

 

[79jasper]

Yes, but I'm thinking he was asking why gary thought his needed bled. Ie, maybe had a line off, ran low on fluid, etc.

Sent from my SAMSUNG-SM-G890A using Tapatalk

 

[riotwarrior]

Or as he does...ask questions to answer a question...

 

[icanfixall]

Reason I'm asking is I do not know when to bleed air from this valve. I know we bleed from the farthest from the master but when do we do this valve? I replaced mine some time ago but have had braking issues since. What happens is in a sudden application of braking I get a very short skidding of either one or both rear tires. Then nearly no braking at all. It feels like I lost a hose. Also no matter how slow I apply the brakes if the rears lock up the same issue happens. No braking. Well at least I feel like I have nothing working up front where most of the stopping is done. It definitely is in the RABS valve.

 

[ifrythings]

Rear right, rear left, abs valve then front right, front left.

Abs valve does not need to be vacuum bleed to remove air from the dump valve as that is the part that's spring loaded.

 

[JLtoolman]

My F350 has been doing that since it was new. It will scare the crap out of you, if you are not expecting it (and sometimes when you are). I took mine back to the dealer three times, about this "problem". Each time, "technicians" drove the truck, and said that is the way they work, and that nothing was wrong with it. I had it happen this morning on the way to work, when traffic went from 60 mph to 0 mph suddenly. Mine is worse on wet roads, of course. Even at that, I had cars behind me running of the road to keep rom hitting me and other cars.

If you find a fix, I am interesting in knowing what it is.

 

[OLDBULL8]

Take the cap/plug off where the spring is (Dump valve), remove the spring but leave the piston in, replace plug, cycle the braking 4-5 times, replace spring, try braking, that should have fixed it. There is 45 pages in my 89 manual for trouble shooting the RABS, that's why I asked why GGM-Gary he has to bleed them.

Is the Yellow RABS lite ON?

Is the Red Brake lite ON?

Is the proportioning valve on the rear hooked up?

http://www.oilburners.net/forums/showthread.php?75851-Ive-been-having-brake-issues

But no answer back.

 

[jwsfarrier]

Im glad this question was brought up. I had serious brake issues on my 89 when I first got it. The truck led a hard life with its PO and it seemed no maintenance was done on anything. I had the entire brake system gone through and brought up to par. My brakes damn sure worked better but my anti-lock warning light was still on. I know they did not replace the RABS valve,so considering the condition of everything else, I decided to replace it with one from rock auto. Since I have the engine out it was real easy to get to. I had read that the valves to go bad. Needless to say I havent got around to bleeding the system yet or exactly what the best procedure is. Im hoping by replacing the RABS valve my light will go off.

 

[MTKirk]

When I replaced the RABS unit on my '87 it was a nightmare to get all the air out of it. I pressure bled the entire system per manual (pass, rear, driver rear, rabs, pass front, driver front). I used a pressure bleeder (which I also used to test & verify I had no leaks) and ran through all the bleeders 3 or 4 times. Air kept turning up at the rears and the rabs, I am certain I pushed at least 3 quarts of fluid through the system before I had all the bubbles out. Mostly I think this system is a B*TCH to bleed, and it doesn't work right until it is air free.

My rears will still occasionally lock briefly when I am going very slow on some sandy asphalt, but never at speed, even with the snow plow on.

 

[OLDBULL8]

There are three fuses in the RABS circuit, 1-20 Amp and 2- 15 Amp fuses.

Check the sensor on the rear pumpkin.

Obtain a flash out code.

 

[MTKirk]

I've been wondering if my low speed lock up might be caused by a week signal generated by the Exciter ring, Speed sensor combo.

The theory being that one of them is a permanent magnet (which would lose magnetism from shock & age) and the other ferrous material to generate a current in a magnetic field. If the sensor is the magnet that would be an easy fix, if it's the ring; not so much. 'Course if there's no magnet involved my theory goes nowhere.