RABS valve - where is it???

[SusieQ]

Hi Guys,

I am a bit stumped...Haynes says that the RABS valve is mounted on the driver side frame. I found the control module and control unit, but where the heck is the rabs valve? My brakes are doing the pump/fail trick at low speeds and the abs light comes on daily. Since the brakes are actually being affected, I thougt the valve would be the first thing to change-out. Mechanic agreed, but now I can't locate it. Where is that puppy?
Thanks!

 

[HIX]

silly question.

Have you checked the brake fluid level? I have a small leak in the front and when my brake fluid gets low my truck does exactly what you are describing.

 

[SusieQ]

Yes, that's fine. Even gave it a good bleed to be sure there was no air. Thanks for the suggestion tho'.

 

[HIX]

on my truck the valve is on top of the axle pumpkin.

 

[SusieQ]

That's the one in the back?? I think there are two on the '93s and newer. I am searching for the one in the front, somewhere on the frame...any idea where on the frame? The figure in the Haynes manual puts it just where the frame curves upward towards the wheel. I can't find it. Am I totally off?

 

[TDG]

To the best of my knowledge the 93 and later do not have a RABS valve. In the 4WABS system (93 and later) they use a thing they call a HCU (Hydraulic Control Unit) to cycle the brakes. This unit can be found in the engine compartment on the drivers side behind the radiator mounted to the frame, it looks like a big electric motor mounted on a block with a bunch of hardline connected to it. Just follow the lines from the master cylinder and you will find it. Hope this helps.

 

[SusieQ]

Hi,

Thanks for the input...but there is a separate RABS. Atleast according to Haynes. Thanks for the reply anyway.

 

[TDG]

The manual could be wrong or like my chiltons doesnt bother to mention what applied to what year. (Chiltons shows a RABS valve but doesnt mention that rear ABS was only used on the 91-92 models) From looking at my 92 which has a RABS valve mounted to the frame under the drivers area and comparing it to my 93 which doesnt have a RABS valve but does have 4WABS with a HCU I can safely say that for my application there isn't a RABS valve because everything is controled by the HCU. If you trace the brake line from the braket in the rear where the hose goes to the the axle back and see where it goes, my guess is that you will end up at the HCU, if so then there is no RABS valve. But hey I could be wrong. Good luck.

 

[SusieQ]

Thanks!!

 

[newtek007]

Left Frame Rail

The valve is located on the left frame rail above the rear axle.
The 91 to 92's had RWABS while the 93 up has 4-wheel ABS.
Hope it helps.