ABS delete

[FrankieD61]

I've been looking into deleting the ABS on my truck. The brakes, as most of you know, SUCK.

Will deleting this system cause the brake light to be all the time (it already is for me; I have a trouble code stored in the ABS module)? I was hoping that I could kill 2 birds with one stone: get that brake light out and stiffen up those brakes.

Thanks.

 

[Nad_Yvalhosert]

Year, make, model, 2 or 4wd info please.

Yes and no. Yes the light will be on. No, if the system is in good working order or bled properly, there's no difference in operation or pedal feel.

The ABS isn't your problem, the problem you've neglected to be more specific about...

If the ABS light is on, the electric side of the ABS is deactivated, leaving you with purely hydraulic brakes. If the brakes are poor, it's not ABS related.

 

[Frank Enstein]

I cannot tell you to use a 1975 Camaro proportioning valve due to legal reasons.

See if someone local can bleed them properly before you trash the ABS.

 

[FrankieD61]

Year, make, model, 2 or 4wd info please.

Sorry.

91, Chevy, K1500, 4wd.

I have a Snap-On MT2500 with the ABS cartridge. I've done the ABS bleed with it; no luck. I've adjusted my rear brakes; no luck. My front pads are brand new. All new rubber lines, front and rear. I think I've covered everything you've asked for. Sorry for my lack of detail. It was late, and I just wanted to get the thread started.

If the ABS light is on, the electric side of the ABS is deactivated, leaving you with purely hydraulic brakes. If the brakes are poor, it's not ABS related.

It's the brake light, not ABS light. If I put the E-Brake on, the light gets brighter. Once the E-Brake is off, the light gets dim and stays that way. This usually means there is a trouble code stored within the module itself. I pulled codes. I got one code for the dump valve and the module itself. Also, to add to your comment, while the electronic part of the system may be disabled, the fluid still has to pass through the iso/dump valve, which, if mucked up with 30 year old fluid mixed with moisture will probably contribute to this issue. I could just be talking out my ass though. This is just a hypothesis, kinda sorta.

 

[FrankieD61]

Year, make, model, 2 or 4wd info please.

Yes and no. Yes the light will be on. No, if the system is in good working order or bled properly, there's no difference in operation or pedal feel.

The ABS isn't your problem, the problem you've neglected to be more specific about...

If the ABS light is on, the electric side of the ABS is deactivated, leaving you with purely hydraulic brakes. If the brakes are poor, it's not ABS related.

Also, these trucks are heavy and the single piston caliper is just not enough to stop these things. So you're on to something here.

Idk, let me know what you think.

 

[2drXmobb]

Sorry.

91, Chevy, K1500, 4wd.

I have a Snap-On MT2500 with the ABS cartridge. I've done the ABS bleed with it; no luck. I've adjusted my rear brakes; no luck. My front pads are brand new. All new rubber lines, front and rear. I think I've covered everything you've asked for. Sorry for my lack of detail. It was late, and I just wanted to get the thread started.




It's the brake light, not ABS light. If I put the E-Brake on, the light gets brighter. Once the E-Brake is off, the light gets dim and stays that way. This usually means there is a trouble code stored within the module itself. I pulled codes. I got one code for the dump valve and the module itself. Also, to add to your comment, while the electronic part of the system may be disabled, the fluid still has to pass through the iso/dump valve, which, if mucked up with 30 year old fluid mixed with moisture will probably contribute to this issue. I could just be talking out my ass though. This is just a hypothesis, kinda sorta.

I had a similar problem with the light I had a leak from one of the wheel cylinders. On these trucks if it gets air in the brakes it takes a very long time to bleed out all the air.

 

[evilunclegrimace]

Unplug the RWAL module from the harness. The light will not be on. You can also remove the dump valve by replumbing the rear brake line directly to the combo valve.

 

[Schurkey]

91, Chevy, K1500, 4wd.

Should be Kelsey-Hayes RWAL. Early RWAL had cast-iron body, with a bleeder valve. Later RWAL had aluminum body, no bleeder valve.

I have a Snap-On MT2500 with the ABS cartridge. I've done the ABS bleed with it; no luck. I've adjusted my rear brakes; no luck. My front pads are brand new. All new rubber lines, front and rear.

1. Does your '2500 have an "auto-bleed" for the ABS, so that it pulses the valves? I didn't think the RWAL had an auto-bleed option. It would be nice to be wrong about that. I never had an ABS cartridge. The "Domestic Primary" programmable software would do ABS auto-bleed on my Trailblazer, but not on my '88 K1500 or my '97 K2500. I haven't tried ABS service on the '88 RWAL with my Solus Pro.

2. Do your calipers work properly? I've seen them get really crusty; they "work" but the piston doesn't move as freely as it should. Thus the front brakes don't apply like they should, leading to "weak" braking. Secondary issue--the earlier "regular cab" trucks got JN3 brakes, which have the smallest pistons in the calipers. I don't remember when they got rid of the JN/JB3 option. JN/JB5 calipers are a substantial upgrade.

It's the brake light, not ABS light. If I put the E-Brake on, the light gets brighter. Once the E-Brake is off, the light gets dim and stays that way. This usually means there is a trouble code stored within the module itself.

Am I wrong? If the ABS light is on, you have stored codes. If the BRAKE light is on, you have a pressure imbalance between front and rear hydraulic circuits; which is nearly always air in the system, but could be ABS or faulty master cylinder.

I gotta go verify with the service manual later.

I pulled codes. I got one code for the dump valve and the module itself. Also, to add to your comment, while the electronic part of the system may be disabled, the fluid still has to pass through the iso/dump valve, which, if mucked up with 30 year old fluid mixed with moisture will probably contribute to this issue.

Again, I gotta research this. Seems to me that just the act of pulling codes triggers a code.

If the isolation valve is stuck open, your anti-lock wouldn't work, but you'd have "normal" rear brakes that might lock-up.

If the isolation valve is stuck closed, you've got no rear brakes. The pedal "should" be high and hard. The safety switch would probably light up the (RED) warning light on the instrument cluster. Do the rear brakes get hot if you stop hard from highway speed?

If the dump valve is stuck closed, your anti-lock wouldn't work. It couldn't relieve pressure to get the rear wheels to turn again after locking.

If the dump valve is stuck open, you'll have low, squishy pedal, no or nearly-no rear brake action. Again, the safety switch might trigger the red instrument cluster light.

 

[FrankieD61]

Should be Kelsey-Hayes RWAL. Early RWAL had cast-iron body, with a bleeder valve. Later RWAL had aluminum body, no bleeder valve.


1. Does your '2500 have an "auto-bleed" for the ABS, so that it pulses the valves? I didn't think the RWAL had an auto-bleed option. It would be nice to be wrong about that. I never had an ABS cartridge. The "Domestic Primary" programmable software would do ABS auto-bleed on my Trailblazer, but not on my '88 K1500 or my '97 K2500. I haven't tried ABS service on the '88 RWAL with my Solus Pro.

Yes, the ABS cart has a wonderful feature-set. It works great with my truck. I wasn't cheap, but is was brand new in the box, purchased off eBay.

2. Do your calipers work properly? I've seen them get really crusty; they "work" but the piston doesn't move as freely as it should. Thus the front brakes don't apply like they should, leading to "weak" braking. Secondary issue--the earlier "regular cab" trucks got JN3 brakes, which have the smallest pistons in the calipers. I don't remember when they got rid of the JN/JB3 option. JN/JB5 calipers are a substantial upgrade.

The truck is new to me. I will check on this.

Am I wrong? If the ABS light is on, you have stored codes. If the BRAKE light is on, you have a pressure imbalance between front and rear hydraulic circuits; which is nearly always air in the system, but could be ABS or faulty master cylinder.

I gotta go verify with the service manual later.

Sorry, I didn't mean to come off as condescending. I think in this case, though, the brake warning light serves 3 purposes in my truck: Parking brake reminder, Brake fluid level warning, and ABS Trouble indicator.

Again, I gotta research this. Seems to me that just the act of pulling codes triggers a code.

If the isolation valve is stuck open, your anti-lock wouldn't work, but you'd have "normal" rear brakes that might lock-up.

If the isolation valve is stuck closed, you've got no rear brakes. The pedal "should" be high and hard. The safety switch would probably light up the (RED) warning light on the instrument cluster. Do the rear brakes get hot if you stop hard from highway speed?

If the dump valve is stuck closed, your anti-lock wouldn't work. It couldn't relieve pressure to get the rear wheels to turn again after locking.

If the dump valve is stuck open, you'll have low, squishy pedal, no or nearly-no rear brake action. Again, the safety switch might trigger the red instrument cluster light.

My pedal is exactly as you describe in the last paragraph. Very squishy pedal. Almost as if there was a leaking master.

 

[Schurkey]

Yes, the ABS cart has a wonderful feature-set. It works great with my truck. I wasn't cheap, but is was brand new in the box, purchased off eBay.

I guess I'm overdue to connect the Solus Pro to the '88, then.

I think in this case, though, the brake warning light serves 3 purposes in my truck: Parking brake reminder, Brake fluid level warning, and ABS Trouble indicator.

Yeah, I did some research, and I'm thinking you're right that it does three things. But brake fluid LEVEL may not be one of them. Something is going to warn the driver when the front and rear pressure isn't equal.

My pedal is exactly as you describe in the last paragraph. Very squishy pedal. Almost as if there was a leaking master.

Do the rear brakes get warm when used hard?

Have you tested resistance of the solenoid coils in the ABS unit?

I'd hope that using the scan tool ABS auto-bleed to chatter the valves might clear or unstick them. Worth a try--or ten.