brake light came on in my 88 k1500 but why?

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Swims350

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well not sure on the suqarebodies, but on my newer body style truck it sure does.

As hrpc said I know for sure on the squarebody trucks and vehicles if you got a brake light on and it's not the e-bare(which is another light itself aint it) then it's a pressure difference between front and rear that does it. Since it's only hooked to the prop. valve on the SB vehicles.

Mines like the 92 or so s-10's and stuff has the brake "brain box as I call it next to the MC, and has 2 big weather pak plugins that go to it, and the prop. valve wire is in that harness, but by itself. Then it has a dump or isolation valve mounted next to the prop. valve and under the mc. Since mine is rear wheel only it's supposed to let fluid bypass into the iso/dump valve instead of go to the rear brakes in heavy braking to avoid them locking and sliding. The book says if the light is on for any of it the anitlock goes into bypass and doesn't work. I have read online as well that a bad dump or iso. valve can act like a bad MC and let the pedal travel far before applying brakes, and NOT throw a brake light. I know they aint cheap either, reman. they are about $250. No way for me I'll do away with it. The website I had saved has info on checking it. They said to unhook the line going to the dump valve and run the mc line straight to the prop valve. or the prop. valve line straight to the rear brakes like the older trucks and if the pedal gets firm then it's a bad dump valve, if not it's a bad MC.

Anyone wants some reading check this out...

http://www.aa1car.com/library/abs_kelseyhayes_rwal.htm
 

89Suburban

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****, that's a good read. Where is that dump valve located? I think I had the same issue with my '89 K1500, I replaced every fukin thing in the brake system except for that. Half the reason I went back to a square body. Stupid ass newer **** with all the gizmo's and electronic ********, I can't deal with that ****.
 

HotRodPC

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Yeah, I like bells and whistles too. Cruise, Tilt, Power locks and windows and AC at the bare miniumum.
 

RetroC10Sport

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Might even try to add an airbag, steering wheel controls, telescopic steering column and who knows what else...

Why? Because I like to find something simple and complicate it!
 

Swims350

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the dump valve is right under the master cylinder on mine, right next to the proportioning valve. it looks just like the end of the mc the metal part but shorter and no resivoir.

I'm slowly doing away with all that stuff on mine, already ditched a/c and thinking of removing the abs stuff. Might even do away with power windows and door locks.
 

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