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1991 K5 Brake Valve Assembly, Brake Combination And Bracket

Rhinodrvr

Rhinodrvr

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Need some assistance or direction.

Looking for a replacement Valve Assembly (Proportion Valve) for my 91. The OEM part number is GM part # 15633297. I am hitting a dead in and just not sure where to look. I've tried all of the typical parts sites.

What is causing this hunt is a BRAKE LIGHT (ON) and all of the mechanical parts are checking out. I have disconnected the sensor, ABS module and battery and letting it sit to see if it might rest.

Any thoughts or ideas?

Rhino
 
I used my factory service manual to run down the diagnostic tree. Have you done that yet?
 
Does ABS have it's own lamp, or is BRAKE triggered by both ABS and the combo valve? Is it also triggered by the parking brake switch? I think if you just unplug the connector on the combo valve, that eliminates that input. There's an old process for centering the valve that's used sometimes after repairs or bleeding. To rule out the parking brake, that's either unplugging the switch or jumpering the terminals.
 
Believe ABS error codes are done through the standard "brake" dash indicator.

I believe the ABS is pretty easily bypassed as well, but agree, easiest is to unplug the combination valve. If light doesn't go out, the valve isn't the problem.
 
Have you verified that the parking brake switch is not the problem?
 
Not to add to the diagnostic side, but the chances of you finding the original combo/prop valve for an ABS equipped square are slim and none.

Even if you diag points back to it you can’t get one. As a matter of fact none of the ‘90/‘91 squarebody ABS parts are available from anybody. The EBCM or the combo/prop valve are long gone.

My suggestion would be to delete the ABS completely. Get some brake line, flaring tool and a standard prop valve and just throw the abs stuff in the trash can.

Again I’m not saying that to discourage diagnosis, but if it ends up you need either part you are screwed anyway.
 
ZooMad75 said:
Not to add to the diagnostic side, but the chances of you finding the original combo/prop valve for an ABS equipped square are slim and none.

Even if you diag points back to it you can’t get one. As a matter of fact none of the ‘90/‘91 squarebody ABS parts are available from anybody. The EBCM or the combo/prop valve are long gone.

My suggestion would be to delete the ABS completely. Get some brake line, flaring tool and a standard prop valve and just throw the abs stuff in the trash can.

Again I’m not saying that to discourage diagnosis, but if it ends up you need either part you are screwed anyway.
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Are these parts square body only or the same for same year gmt400s?
I have parted a few of the late 80s early nineties gmt400 and have those parts in case someone needed them
 
imiceman44 said:
Are these parts square body only or the same for same year gmt400s?
I have parted a few of the late 80s early nineties gmt400 and have those parts in case someone needed them
Click to expand...
They are close but not the same. Honestly the rear wheel only abs wasn’t great back then and given the lack of parts availability, it’s just smarter to eliminate it and go back to a non abs system.
 
ZooMad75 said:
They are close but not the same. Honestly the rear wheel only abs wasn’t great back then and given the lack of parts availability, it’s just smarter to eliminate it and go back to a non abs system.
Click to expand...
Oh I totally agree it was a shifty design and I would never have it for me but some people like to keep the vehicle stock so I am asking
 
RWAL Brake system. GM actually got sued several times over late 80's early 90's truck abs. I am with Zoo on this one, eliminate the abs use a standard proportion valve at front cross member.
Unless this is a concourse vehicle.
 
imiceman44 said:
Oh I totally agree it was a shifty design and I would never have it for me but some people like to keep the vehicle stock so I am asking
Click to expand...
Outside of a few of us here, nobody is going to miss the shitty abs system components missing.

Yeah if somebody has an an ultra low mileage minty fresh example and the system works, sure leave it. But even on the same truck if something did fail I’d still yank it. It’s not hard to swap it with earlier parts and make it look 100% OEM correct just an earlier version correct. Even then only the biggest squarebody nerd would notice it’s gone.
 
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