anyone been able to re-center your brake warning light? 73 Chevelle SS

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anyone been able to re-center your brake warning light? 73 Chevelle SS

Post by clanceman427 on Tue Apr 25, 2017 9:46 am

My car is all original, and last year I had to replace the metal rear brake line since it rusted thru and started leaking brake fluid right near the trans crossmember. The light got activated properly to alert me to the issue. But now I've replaced the line, and re-bled the brakes and the light is not recentering. The factory manual says something like it takes around 400psi to reset and recenter the warning light switch, but I haven't been able to get the light to go off.

I tried bleeding the front drivers side caliper, but when I did it I did not have that little button depressed on the front of the combination valve. Is that needed to be depressed while bleeeding the brakes? I was able to bleed them without having that button depressed, but maybe it needs to be depressed while bleeding to get the light to recenter?
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Re: anyone been able to re-center your brake warning light? 73 Chevelle SS

Post by pila on Tue Apr 25, 2017 10:56 pm

I had this happen only once, may years ago, and If I remember correctly, just opening the bleed through button on the combination valve would balance the front & rear. (?)
Everything on my Elco is new, but didn't have the light come on after bleeding all the brakes, so it's hard to say what's going on.

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Re: anyone been able to re-center your brake warning light? 73 Chevelle SS

Post by clanceman427 on Tue Apr 25, 2017 11:09 pm

Thanks Bill. I think my next attempt will be to bleed the brakes while that bleed thru button is held depressed. The Factory manual shows a tool that bolts onto the combination valve to hold it depressed while bleeding the brakes. I'll make something to hold it down an bleed the brakes and see if that works.
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Re: anyone been able to re-center your brake warning light? 73 Chevelle SS

Post by Hs1973 on Wed Apr 26, 2017 12:28 pm

I have just been trough all those brake issues on my chevelle. I bleed my brakes a few times and the light shut off when we did it the last time with the little button pressed in. I have a little pair of pliers that i can lock i use on the button to hold it in. Its Way to hard to hold it with a finger, and it would take someone to lay under the car doing it. So try it again with the button pushed in, i was told that the light would not go out as long as there are air trapped in there.
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Re: anyone been able to re-center your brake warning light? 73 Chevelle SS

Post by clanceman427 on Wed Apr 26, 2017 2:02 pm

Thank you very much Hs1973, that gives me hope!
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Re: anyone been able to re-center your brake warning light? 73 Chevelle SS

Post by pila on Wed Apr 26, 2017 2:02 pm

Supposedly (!) the shuttle valve in there moves to the side with less (or no) pressure on that side, as in a leak etc on that side, making the fail light come on. Of course the parking brake turns the light on also if it's not all the way released......

Isn't this fun hahaha !

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Re: anyone been able to re-center your brake warning light? 73 Chevelle SS

Post by clanceman427 on Wed Apr 26, 2017 2:07 pm

Good point Bill!
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Re: anyone been able to re-center your brake warning light? 73 Chevelle SS

Post by pila on Wed Apr 26, 2017 10:29 pm

I would think that applying the brakes with the button pushed may let the shuttle center it self (?) might be worth a try Very Happy

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Re: anyone been able to re-center your brake warning light? 73 Chevelle SS

Post by clanceman427 on Wed Apr 26, 2017 10:59 pm

I did try that, with me underneath holding the button and a helper pushing the brakes while the engine was running (for full vacuum assist), no go. That didn't recenter the shuttle. But Hs1973 says it's hard to push the button, so maybe I was only compressing the rubber cover but not moving the important part underneath? I'll mess with it some more.
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Re: anyone been able to re-center your brake warning light? 73 Chevelle SS

Post by Hs1973 on Thu Apr 27, 2017 8:20 am

You are welcome. It is hard to get it to behave, ive had problems every time i have had to mess with the brakes. Maybe your Block is keeping the light on because it is old and it has a little rust on the inside? It is not the smartest invention gm made. There is only one thing you can do, and that is to keep trying. I have had to try it several times before it works. Only one time have it worked the first time. Hope you get it done.
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Re: anyone been able to re-center your brake warning light? 73 Chevelle SS

Post by Mcarlo77 on Thu Apr 27, 2017 11:44 am

[quote="Hs1973"] It is hard to get it to behave, ive had problems every time i have had to mess with the brakes.


It's too late for this if the spool is already off-center...but, for future reference, this handy little tool saves all kinds of frustration when servicing/bleeding brakes. I used it when overhauling my brakes and it worked like a charm.

http://www.ebay.com/itm/Combination-and-Prop-Proportioning-Valve-Bleed-Bleeder-Tool-PVBT-/172363944693?hash=item2821b112f5:g:XT0AAMXQVT9TBk9g&vxp=mtr
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Re: anyone been able to re-center your brake warning light? 73 Chevelle SS

Post by Tquillen on Thu Apr 27, 2017 10:48 pm

I made one of those tools on my lathe out of a fine thread bolt. Works great!

As far as re-centering the spool, I wrestled with this on my C10 where I used a non factory combination valve. After bleeding. mashing, bleeding some more, I finally called a friend of mine who told me to press the brake pedal quick and HARD with the engine running, as hard and as fast as I possibly could. Would you believe, it did the trick?

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Re: anyone been able to re-center your brake warning light? 73 Chevelle SS

Post by Hs1973 on Fri Apr 28, 2017 5:33 am

I guess it is worth trying next time. I made my own tool from a pair of old wisegrips. I put a piece of rubber on the jaws, and take care it is not to tight. I have always Got it to work soner or later. But it sure is a pain. I have installed speed bleeders in all 4 corners, so i can bleed the brakes on my own. It makes it just a bit easier not having to find a friend with time to help when i need it.
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Re: anyone been able to re-center your brake warning light? 73 Chevelle SS

Post by clanceman427 on Wed May 03, 2017 10:30 pm

Just got done spending time trying to recenter my combination valve. I could not get that button to budge, even tapping with a hammer. I removed the protective rubber cap from the button, and I noticed that there was dry rust marks on the inside of the rubber cap. I'd guess that the button has never been pushed in the entire life of this car, and I think the button is frozen with corrosion. I'll just deal with the light until the big restoration commences.

So I gained no ground on the combination valve, but I did have a chance to remedy my reverse lights, so that is a small win. The reverse lights not working was bugging me. Little things along the way Smile
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Re: anyone been able to re-center your brake warning light? 73 Chevelle SS

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