"Brake" warning light came on...

[steves1967]

The Brake warning light came on today in my 90 suburban, haven't touched the brake system in months, checked the fluid level and it's fine, burb seems to still stop fine..what should I check?? Thanks- Steve

[beaterC10]

Have you made any real hard stops? There is a switch in the proportioning valve that causes the light to illuminate. It happened a few years back on my 84 after I made a real hard stop. There is a way to reset the switch, I will try to find it in my shop manual.

Dave

[steves1967]

Thanks Dave, the light came on while i was driving down the freeway- I can't figure it out, I jacked up the burb started the engine, put it in gear and checked all 4 tires, they all seem to stop fine. Brake fluid was changed about 4 months ago, and still looks good. I don't have any leaks that I can find and my driveway is still cleaN, LOL...

[1970c10sb]

Ive got the same problem with my light on my 76 k20. it comes on randomly but all i have to do is tap the brakes and it goes off. my father in law said my prop. valve was bad and needs replaced, but hey-- it still stops LOL

[Grim Reaper]

Only two things cause that light to come on those two years. The balance valve that detects loss of pressure in a circuit or the parking brake.

Unplug the wire going to the combination valve on the driverside front cross member near the steering box. If the light goes out then the switch is tripped OR the switch is bad.

If somehow it has been tripped then bleed the brakes and see if it goes away. Most of the time that will cause the shuttle in the CV that trips the light to recenter.

[STEVE A WILBURN]

My 88 ,if I Just Put My Foot On The Brake Just A Little Or A Little At Start Up The Light Will Come On. Gm People Told Me To Unplug The Cable Under The Master Cylinder For About 2 Min To Reset Everything.that Was In 1988 I Still Used It Today.

[383drvr]

I was dealing with this same problem here about a month ago and everyone here helped me fix it.

Something tripped the switch, so you need to find the problem. The shuttle inside the proportioning valve detected a variation in pressure between the four wheels, setting off the safety alert thing. I doubt its a switch malfunction. Mine was hard to diagnose, but you need to check all four wheels from the inside out and look very carefully. It wont drip onto the driveway, you need to look for moist spots around the connections, as well as rings of dried oil that may have flung from the wheels while driving. (was the case for me). My rear drum piston seals were worn, and leaking when I braked on the road, causing the variation in pressure in the lines- tripping the light circuit. Since I was rolling, the oil from the calipers dripped onto the spinning wheels and flung it onto the wheelwells. Hard to see so you have to look- thats why I didnt catch it at first. Finally, I replaced the seals, (brake pads too while it was all apart), and bled all four wheels and changed the fluid. Took me half a Saturday and I took my time too. The light reset itself after a few hours of driving. I must have had this problem for a while, because now my brakes work so well I am constantly locking up the rears now.

There is also a reset button on the end of the proportioning valve that may work somethimes. You have to get under the car and feel for it on the end of the valve. I dont thing you can see it.

Check your wheels again, I bet its the seals.

Let us know how it goes.

[RockHQ]

if there is no fluid loss, and judging from what you said there isn't, you might want to check the brake shoe distance from the drums. If they're too far away the warning light be tripped.

[Grim Reaper]

Originally Posted by 383drvr

There is also a reset button on the end of the proportioning valve that may work somethimes. You have to get under the car and feel for it on the end of the valve. I dont thing you can see it.

There is no "reset botton".

That's to aid bleeding the brakes. You dont push the center either. You push the end without pushing the center and it exposes the pin in the center. The pin will have a notch. If you have the tool then it engages the notch and pulls the pin out about 1/8 of an inch to release the hold off valve in the Combination valve. If you dont have the tool then you can grab it gently with vice grips (that's a oxy moron) or wedge something in there or use a small c-clip.


I have pictures of a disassembled "Combination Valve" in a write up HERE towards the bottom. Its a "combination valve" it has a "proportioning valve" in it for the rear circuit.

[383drvr]

Thanks for that explanation. I wasnt fully sure how that button worked and why. (obviously) :p

[Grim Reaper]

Originally Posted by 383drvr

Thanks for that explanation. I wasnt fully sure how that button worked and why. (obviously) :p

It's a totaly misunderstood thing on how that thing works.

[steves1967]

Thanks guys, I'll check it out tomorrow afternoon, I did notice some "spots" on the inner wheelwells, thought it was just road grime- but now i think differently. THANKS!!