ABS / Hydraulic Brake Valve

LarryA · Post by **LarryA** » Sat Mar 31, 2007 3:58 pm

On a 1990 Bronco II, is there a way to test the rear ABS Hydraulic valve to see if it is working? I found there is no hydraulic pressure to the rear wheels when I replaced the rear brakes and went to bleed the lines. I have fluid pressure at the master cylinder and the inlet to the valve but nothing at the outlet of the valve. It makes no difference on the ingnition switch position or engine running or off. I've never seen this and at this point can only think the valve must be bad. At over $100 for rebuilt, this is an exspensive part to replace on a hit or miss situation.
Appreciate any help here. Thanks

greenmachine89 · Post by **greenmachine89** » Sat Mar 31, 2007 6:29 pm

The valve you are thinking of could be stuck allowing only fluid to drain up front but not in the rear. Try pumping the brakes quick a couple of times. That will knock it back into place. If that does not work start the car and pump it will help of the vacume booster. Dont forget to adjust your rear brakes!

LarryA · Post by **LarryA** » Sat Mar 31, 2007 10:40 pm

The brakes were pumped many times during the time I was trying to get fluid to the rear line(s). It was tried with the engine running and off. Nothing worked. I never saw this before and at this point have to think the valve is indeed stuck in the closed position. I'm just hoping that it is only the valve. I wish I knew though, if it could be checked by testing the electrical terminals or by jumping with power but I'd have no idea which terminals need to be crossed.

LarryA · Post by **LarryA** » Mon Apr 02, 2007 12:46 pm

Still no luck.
Replaced valve with another and same thing (no pressure to rear).
Checked Speed Sensor and it reads good with resistance of 1.340 OHMS (should be .08 to 1.4 to be acceptable).
ABS Module is supposed to Self Test at Startup and keep the Anit Lock light on if there is a problem. The light goes out after a few seconds as it should. You can't even get diagnostic codes unless the light stays on (according to my manual).
Really could use some help here......

greenmachine89 · Post by **greenmachine89** » Mon Apr 02, 2007 11:15 pm

Wow I believe that I also am stumped! You can start at the top by cracking open the line to the rear at the master cylinder and go on from there untill you find no pressure but it sounds like to me that your master is the problem.

tekatlarge · Post by **tekatlarge** » Tue Apr 03, 2007 10:35 am

Have you thought to check the flexible line to the rear diff.

I have seen many flexible brake lines fail internally and block the flow of fluid. Loosen the line at the hard end on the frame and see if you then get fluid!

LarryA · Post by **LarryA** » Tue Apr 03, 2007 12:28 pm

FIXED! Don't know what exactly was wrong yet but I took another vavle fromthe boneyard and before doing anything I blew compressed air through the valve and it went through fine. Installed the valve and the brakes bled fine. Test drove and Anti Lock plus red brake light were ON. Stopped and plugged the valve back in and lights went out. Drove some more then came back and jacked up therear. Had wife depress brake pedal and good brakes. Evidently the valve I had put on is stuck closed as was the original. That's my only guess. Going to see if I can open the stuck two but at any rate, it is now fixed and working. Ran down to the last minutes as my time went but turned out ok and at a cost of only $57 for everything new in the rear drums and the vave costs. Much better than labor at a shop!
Thanks for the inputs.