Bypass the anti-lock brake module?

[Declaration Day]

There are no vehicle inspections in Michigan.

[never_retreat]

I can remember removing many first generation ABS deally things of several mid 80's ford pickups.
Brakes were squishy with them perfect without without.

[Declaration Day]

Ok, time to revive my thread.  I am doing the ABSectomy today.  I received my proportion valve in the mail, and am about to start removing brake lines.

A full write-up with pictures will follow, possibly by this evening, assuming I don't crash and burn in a fiery ball of death during the test drive.

Wish me luck.

[Tallpine]

A full write-up with pictures will follow, possibly by this evening, assuming I don't crash and burn in a fiery ball of death during the test drive.

Be sure to have someone take a video 

[Declaration Day]

Success!  Total cost, about $85 (vs. almost 600).  Pictures and write up are coming, after I take a badly-needed shower.

[Jim147]

Good job. Glad to hear you got it working.

jim

[Declaration Day]

Ok folks, here's what I did:

These first two pictures are the ABS module.  It's leaking, badly.......and costs $560.....






These next two pictures are the proportioning valve (to limit the amount of pressure going to the rear wheels), and the spot next to the brake master cylinder where it will go.  In case you're wondering, the blue / red wire harness is for the snow plow.








These are the brake lines that will be used to bypass the ABS module.  The rear wheels have one input line and one output line to service both wheels.  The front wheels have one input line, but a separate output line for each wheel, thus the three lines connected by a T-connector.  I ended up eliminating the third line, choosing instead to attach the bottom end of the T-connector directly to the original output line.  I figured the fewer connections, the better.







First, I installed the proportion valve.  I removed the rear wheel input line from the brake master cylinder, bolted it to the output port of the valve, and installed a short piece of line between the master cylinder and the input port of the valve.









Next I removed the ABS module.  First I pulled the five brake lines from it, then unbolted it from the frame (3 easy to reach bolts), and finally removed the two electrical connectors.







Here you see where the input / output lines used to connect to the ABS module.  The front input line has a plug in it to prevent the brake master cylinder from leaking out.  If that happened, I'd have to bleed the air out of the master cylinder.  Not fun.





Here the new brake line pieces are installed.





After this, it was just a matter of bleeding out the brake lines, topping off the fluid, then test driving the truck to find the right setting for the proportion valve.

Most days I am just an average working-class honkey.  Every once in a while, I am an average working-class honkey who accomplishes something!  

[eyebrows]

Whats supporting the brake lines? Being screwed into the ABS dohicky obviously supported them before but in your after picture it looks like they are just hanging there. If they can bounce around you might have other problems down the road.

[Declaration Day]

Off to the top right, just out of view, is a retaining clip that holds all 5 lines in place.  And there is a similar clip about every 12-18 inches up the line.  I will probably brace them up tomorrow with some thick zip-ties, just to be on the safe side.  Nonetheless they are very rigid, and aren't as close to hitting something as the picture suggests.

[zahc]

Here's the $64 question I have about both ABS modules and brake proportioning valves. Bear with me.

The brake master cylinder does not have a return line, as far as I know. So, when an ABS module 'modulates' a caliper/drum, where does the pressure 'go'? I mean, it would be a simple matter if you could use a pressure regulator to 'vent' some of the fluid away from the target, but where do you vent it to? If you tromp down on the brakes and ABS tries to modulate the pressure going to one of the calipers, it can't just close the connection with a valve. Nothing would happen. I can't conceive of a regulator design that can reduce the downstream pressure without having somewhere to vent the excess.

[Declaration Day]

Perhaps the ABS module has its own reservoir?  The one I pulled off looks like it might. 

[CNYCacher]

Here's the $64 question I have about both ABS modules and brake proportioning valves. Bear with me.

The brake master cylinder does not have a return line, as far as I know. So, when an ABS module 'modulates' a caliper/drum, where does the pressure 'go'? I mean, it would be a simple matter if you could use a pressure regulator to 'vent' some of the fluid away from the target, but where do you vent it to? If you tromp down on the brakes and ABS tries to modulate the pressure going to one of the calipers, it can't just close the connection with a valve. Nothing would happen. I can't conceive of a regulator design that can reduce the downstream pressure without having somewhere to vent the excess.

It think it pumps it back at the cylinder.
As evidenced by the feeling of the brake pedal pushing back against my foot last time the ABS kicked in on me.

[Tallpine]

Congratulations!

Besides fixing the leak, you have now taken back the braking control of your own pickup.   


Now, if I could just figure out how to disable the "traction control" on our little car.  It will just shut down the engine half way up a hill 

[Hawkmoon]

Congratulations!

Besides fixing the leak, you have now taken back the braking control of your own pickup.   


Now, if I could just figure out how to disable the "traction control" on our little car.  It will just shut down the engine half way up a hill 

One more reason I'm looking for a clean, low-mileage Jeep Cherokee ... withOUT ABS. In a Cherokee, "traction control" is a function of how hard I press with my right foot. Which is the way it should be.

[zahc]

It think it pumps it back at the cylinder.
As evidenced by the feeling of the brake pedal pushing back against my foot last time the ABS kicked in on me.

OK, I guess that's could be how ABS modules work, since they are powered. But I'm not sure how a passive proportioning valve could work, still.

[Hawkmoon]

OK, I guess that's could be how ABS modules work, since they are powered. But I'm not sure how a passive proportioning valve could work, still.

Not well at all, frankly. Since the proportioning valve on my pickup exploded and has been removed, I have MUCH better braking all the time and I'm a happy camper.

[Declaration Day]

I forgot to mention that my instrument cluster is lit up like a Christmas tree now with idiot lights.  I'll pull the bulbs tomorrow!

[zahc]

That's the spirit!

But might you be able to hack the old ABS module or the wires that plug into it so that it reports proper function?

[Declaration Day]

Maybe, but pulling bulbs is easier!

[zxcvbob]

Is the point of a proportioning valve that it's adjustable?  If not, they could accomplish the same thing a lot cheaper just by putting smaller diameter cylinders on the rear axle, or have two different size pistons in the master cylinder and use the larger (?) one for the back brakes.

(I don't think my old 3/4 ton truck had any of that fancy-pants stuff, and it had amazingly good brakes.)

[Brad Johnson]

Maybe, but pulling bulbs is easier!

Try pulling the ABS fuse first.

Brad

[Declaration Day]

Did that before pulling the module.  It also trips the light.  But thanks for the suggestion!

[Brad Johnson]

Might do some interwebz searches to make sure that pulling bulbs won't cause other problems.  In some models of vehicles yanking the Service Engine bulb can cause no end of havoc.  No idea if pulling the ABS bulb will do the same, but it can't hurt to check it out.

Brad

[Declaration Day]

Well then I will remove the gauge cluster lens and put a small square of black electrical tape over each one. 

[zahc]

Back from the dead.

I recently bought a '96 Tahoe and the brakes ain't right. I'm trying to troubleshoot it and the next thing I'm doing is yanking the ABS. On mine the ABS module is right on the left front fender. I unplugged all the electrical plugs from the ABS unit, and when I start the truck, the only change is the ABS light on the dash doesn't come on at startup, or stay on, or anything. It's like the ABS isn't even there, as far as the computer is concerned. And the brakes feel the same. So since it's just sitting there now unplugged I'm yanking it out tomorrow.

I'm worried I may need a proportioning valve, though. What brand/type did you buy? Is it a single inlet/single outlet valve just installed on the rear brake line (I'm pretty sure from the pictures). Are you adjusting it down a lot/do you think it's necessary?

I want to get my brakes fixed this weekend but don't want to disable my truck then find out I need to wait for a valve to come in the mail.