Ok so I have a 2000 ford ranger 3.0l flex fuel rwd with weak rear drum brakes. I adjusted the shoes to as tight as I can. When I try to brake the rear wheels spin a bunch when jacked up. Pumping the brakes gets the rear wheels to stop, and so does the emergency brake which brakes very well. Front brakes have tons of power however pedal seems soft. I've done a master brake cylinder check by pumping the brake pedal when the cars off, and it holds until you start the car with brake booster. Then the pedal kinda sinks a little more then I think it should, but I still have good front brakes. Now I'm pretty sure the car had ABS but someone removed it. I still have the ABS box. I have normal calipers and rotors on the front wheels without sensors. The car shows ABS light on dash with startup then goes away. So I'm kinda thinking I might have an air bubble in the abs. I've bled the brakes and there was no air. I replaced rear brake cylinders like a year ago, and they don't leak. I've tried the rear cylinders out with the drums off, and they push the pads out very far. I think they're just weak which is why pumping the brakes helps. What I'm wondering is does anyone think its ABS bubble, master cylinder or brake booster? If it's ABS air bubble since I have no sensors I can't just step on the brakes to activate ABS. Which i'm wondering if there's another way to activate ABS without a scan tool in that situation? Thanks.

 

Welcome to the forum

If you just have Rear ABS(RABS) then yes there could be an issue in the ABS unit, its in the drivers side frame rail just under firewall area, you can follow the front brake line from the master down to the ABS unit

Here is a rebuild article: https://www.therangerstation.com/for...-valve.133050/

It reads more like a clogged ABS unit than air in the unit, as RABS are much different than 4WABS as far as getting air trapped inside

You can clean it out as shown in article, or you can by-pass it and add an adjustable proportioning valve so you can set how much back brakes you want

As long as the unit is plugged in to its wires ABS light will stay off


The Master does have two brake lines, front is for rear brakes back is for front brakes
This is because if a brake line should leak/break you won't fully lose BOTH axles for braking, you can keep pumping and the non-leaking axles brakes will still work, but pedal would keep going down to the floor as fluid was being pumped out the leak

So there are TWO seals on the piston in the master, one for front line and one for rear line
It is possible for a seal to leak, so you get good pressure at the front brakes but low pressure at the rear, instead of the fluid being pushed into that brake line its pushed back up into reservoir thru the leaking seal as pressure goes up, it would seem OK when bleeding, no pressure, but not work well when braking

 

Oh you know I think I was mistaking the Proportioning/RABS valve for the ABS pump. Which is why I thought I had ABS also with the dash light. There's a small brake line box with an electrical connector in the middle under the vehicle, but it doesn't look big enough to be an ABS pump. I guess ill clean the Proportioning/RABS valve then, thanks.

 

I took the RABS valve apart, cleaned it, and now the rear brakes have enough power to stop. Just not sure if it's a good front to rear ratio yet until some driving. Thanks for the help.

 

Good work

Thanks for the Update

 

Nice, how i can clean the RABS valve?

 

Read here: https://www.therangerstation.com/for...-valve.133050/

It just shows the parts that come out

 

Thanks