Abs delete problems

[your mom]

I've got a 97 k1500 silverado, my abs went out so I deleted it with a proportioning valve. I did everything right, no leaks, brakes work great, don't have a spongey pedal anymore, but at a red light it's as if I'm pushing the gas pedal, I have to put all my weight on the brake pedal and the truck still inches forward, I've started putting it in park at red lights cause it won't stay stopped. Any thoughts or ideas would be appreciated.

New brake booster, new gmt800 cylinder, new calipers, everything in rear drums new, new rubber hoses on the front, rear still has old hoses but basically my entire brake system is new besides that

 

[El Tigre]

Replacing everything at once makes it almost impossible to find the problem.
Why the GMT800 cylinder? Was it "bench bled"? I got rid of the proportioning valve in favor of a 10# residual pressure valve.

 

[RichLo]

Its been proven here that if you just do the GMT800 master with GMT400 other components it'll be worse than the 400 master. You can either upgrade calipers and wheel cylinders to GMT800 or put a GMT400 master back on it.

The 400 master will be the cheapest and easiest option for sure. And yea, be sure to bench bleed it thoroughly before installing. It makes a difference.

 

[Schurkey]

97 k1500 silverado

my abs went out so I deleted it with a proportioning valve.

Not the best possible solution. Even an entire combination valve would be a less than optimum.

I did everything right

Obviously not.

at a red light it's as if I'm pushing the gas pedal, I have to put all my weight on the brake pedal and the truck still inches forward...

...New brake booster, new gmt800 cylinder, new calipers, everything in rear drums new, new rubber hoses on the front, rear still has old hoses but basically my entire brake system is new besides that

1. WHICH "new brake booster"?
2. The GMT800 master cylinder is almost certainly a mistake of great importance.
3. WHICH "new calipers"? Low-drag?
4. Are the rear brakes properly adjusted? Does the park brake work, and do you use it frequently?
5. How many "old hoses" in the rear? Do the rear brakes bleed nicely, good volume of fluid out the bleeder valve?
6. What is the idle speed of the engine?
7. Are you running oversized tires?

Replacing everything at once makes it almost impossible to find the problem.

Certainly makes it more difficult, anyway.

Why the GMT800 cylinder? Was it "bench bled"?

Bench-bleeding a master cylinder takes more time and effort than most folks realize.

I got rid of the proportioning valve in favor of a 10# residual pressure valve.

Also not an optimal solution, particularly when braking hard. Did you disable the brake-pressure warning light on the dash? Did you remove the holdoff valve that balances front/rear brake pressure when the brakes are first applied?

Its been proven here that if you just do the GMT800 master with GMT400 other components it'll be worse than the 400 master. You can either upgrade calipers and wheel cylinders to GMT800 or put a GMT400 master back on it.

True enough for any low-drag GMT400 calipers. Less true for the JB/JD7, 8, and JF9 calipers.

But yes, the larger bore of the GMT800 master cylinder isn't helping any, the hydraulic advantage is lessened so there's less brake pressure holding the brakes on.

The 400 master will be the cheapest and easiest option for sure. And yea, be sure to bench bleed it thoroughly before installing. It makes a difference.

Absolutely. We're probably looking at the 1 1/8" bore master, with the 40mm Quick Take-Up bore.

There's a smaller master cylinder for the older JN3 low-drag calipers.

 

[Caman96]

Yeah, it’s not the same as Lego’s, where just because it snaps in, and you should.

 

[Alteca]

Yeah I had the same issue pushing through the brakes with an 800 master cylinder. The master was the only variable changed at the time so I’m almost certain that’s what it was.

 

[your mom]

Replacing everything at once makes it almost impossible to find the problem.
Why the GMT800 cylinder? Was it "bench bled"? I got rid of the proportioning valve in favor of a 10# residual pressure valve.

I didn't replace everything at once, just added the proportioning valve and front hoses this time, everything worked fine before the abs went out

 

[your mom]

I didn't replace everything at once, just added the proportioning valve and front hoses this time, everything worked fine before the abs went out

And I heard the 800 master cylinder would give me better braking, it was bench bled correctly

 

[Schurkey]

And I heard the 800 master cylinder would give me better braking

Not gonna happen on Low-Drag calipers. I really wish the Forum owner/moderators would revise the various posts that suggest that as an "upgrade".

 

[El Tigre]

That would assume they have that knowledge, experience, and of course time.
Why do we recommend doing some research into mixing/matching parts from other vehicles based on what "some guy said". Because the systems designed/installed on these vehicles work pretty well the way they are.