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Topic: Proportioning valve issue

in Forum: C3 Handling Components


Proportioning valve issue

Posted: 5/14/13 8:11pm Message 1 of 9
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Vancouver, WA - USA
Joined: 8/25/2005
Posts: 869
Vette(s): 1976 Silver/Firethorn. L48, 4spd. Original 2 bolt, vortec heads, 9.4:1 CR, Speed Pro Cam: 224/224@0.050, 112 LSA, Eagle Steel Crank.
My brake light on the dash is on when the key is in the run position. I haven't driven or started it in months, but I recently had the back calipers off (parking brakes) and then bled all four corners. I have a nice hard pedal. I know it's not the parking brake handle switch - light turns off when I disconnect the wire at the valve and then behaves normally per parking brake application. Something seems to have caused the valve to go off center. I've tried kicking the pedal hard a few times - no luck. Should I re-bleed first? Can you have air in the lines and still have a hard pedal?



 

1976 Silver/Firethorn.  L48, 4spd.  Original 2 bolt, vortec heads, 9.4:1 CR, Speed Pro Cam: 224/224@0.050, 112 LSA, Eagle Steel Crank.
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Re: Proportioning valve issue

Posted: 5/15/13 5:18am Message 2 of 9
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Woodland, WA - USA
Joined: 10/14/2003
Posts: 1171
Vette(s): 1977 T-Top,350,Auto Black Ruby Pearl,Steeroids R&P conversion
When I first bought mine the rear brakes did not work, and could not get it to reset with the normal two person bleeding. I purchased a vacuum bleeder. Bled each wheel stepped on the pedal light went out. I have since made a power bleeder and bleed that way. I see you live in Vancouver I am in woodland and work at Pauls cigars mon Fri mornings If their are no better instructions coming you can borrow either to help you out. How I found out my back breaks where not working was during a smog check after the test in drive and I let off the gas and put on the breaks the rear wheels would not stop buba had disconnected the wire at the valve. but I digress. If you want to try vacuum or power bleeding shoot me a PM and I will give you my phone number and we can meet some where.


Re: Proportioning valve issue

Posted: 5/15/13 9:54am Message 3 of 9
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Duncanville, TX - USA
Joined: 11/8/2003
Posts: 20218
Vette(s): #1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/ Am-Fm/map light National/Regional/Chapter NCRS "Top Flight" #2-1985 Bright Red/Carmine Cp.L-98/auto Member: NCRS, NCRS Texas, Corvette Legends of Texas
Kickin the pedal hard with the engine running, right? If that doesn't center the valve, you may indeed still have some air in the brakes somewhere....and a pressure bleeder is the best way to bleed them.
If you're certain there is NO air in the system, then the valve may be bad.
I would certainly do a pressure bleed on all 4 first, anyway, just to be sure. You could have air on the front or rear side of the system, and still have a hard pedal, if the valve has flipped....which is how it's s'posed to work, anyway. The valve will sometimes flip when bleeding using the pedal, if yer foot goes all the way tot he floor while bleeding. That's why it's best to not go all the way down with the pedal when bleeding....just go almost all the way down.Thumbs Up


Joel Adams
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Re: Proportioning valve issue

Posted: 5/15/13 12:08pm Message 4 of 9
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Woodland, WA - USA
Joined: 10/14/2003
Posts: 1171
Vette(s): 1977 T-Top,350,Auto Black Ruby Pearl,Steeroids R&P conversion
That's a good point by backyard training was always to push pedal to the floor I need to put that bit of info into my rusty trap.


Re: Proportioning valve issue

Posted: 5/15/13 12:13pm Message 5 of 9
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Vancouver, WA - USA
Joined: 8/25/2005
Posts: 869
Vette(s): 1976 Silver/Firethorn. L48, 4spd. Original 2 bolt, vortec heads, 9.4:1 CR, Speed Pro Cam: 224/224@0.050, 112 LSA, Eagle Steel Crank.
Joel, uhhh nooo, engine off.  What's the reason for engine on?  Will the booster help center the valve?  I was using a combination of vacuum and gravity to bleed.  (Vacuum to get it started and then let it drip for awhile).  Full disclosure: for the backs at one point I let the level M/C get pretty low.  There was still fluid in there, but it was definitely too low.  Hopefully I didn't get air in the M/C.   
 
Bob, thanks.  I might be interested in borrowing that pressure bleeder if I can't get it to center by kicking it.  I'll let you know -- will call or PM you for arrangements. 




 

1976 Silver/Firethorn.  L48, 4spd.  Original 2 bolt, vortec heads, 9.4:1 CR, Speed Pro Cam: 224/224@0.050, 112 LSA, Eagle Steel Crank.

Re: Proportioning valve issue

Posted: 5/15/13 1:37pm Message 6 of 9
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Duncanville, TX - USA
Joined: 11/8/2003
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Vette(s): #1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/ Am-Fm/map light National/Regional/Chapter NCRS "Top Flight" #2-1985 Bright Red/Carmine Cp.L-98/auto Member: NCRS, NCRS Texas, Corvette Legends of Texas
rraider1 said: That's a good point by backyard training was always to push pedal to the floor I need to put that bit of info into my rusty trap.


Ya...natural tendency is to mash it all the way down. However, at that point, you will have pressure on the other end of the brake system, front or rear, and with the end you are bleeding open, with NO pressure building, the valve can flop.
Another "trick" I learned from a brake guy years ago was to open the bleeder(with a hose on it), and have someone pump the pedal several times quickly, then close the bleeder. This supposedly gets the most amount of fluid to the caliper/cylinder the fastest. Saves time....so he says. I've done it like that a few times, and it does get the fluid flowing quicker. This is best used when you have replaced the master, or are just flushing the system.



Joel Adams
C3VR Lifetime Member #56    

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Re: Proportioning valve issue

Posted: 5/16/13 10:31am Message 7 of 9
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Manteca, CA - USA
Joined: 11/20/2005
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Vette(s): 1978,two tone,Metalic Rootbeer & gold 1975 L48 4 speed
 Had the same issue with my '81 once. No symptoms except the brake light on. Changed the proportioning valve and the light went out.


Re: Proportioning valve issue

Posted: 5/30/13 11:18pm Message 8 of 9
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Vancouver, WA - USA
Joined: 8/25/2005
Posts: 869
Vette(s): 1976 Silver/Firethorn. L48, 4spd. Original 2 bolt, vortec heads, 9.4:1 CR, Speed Pro Cam: 224/224@0.050, 112 LSA, Eagle Steel Crank.
As of just now, things are working.  Big smile  Put it back on the jack stands tonight, took the wheels off and bled once again.  I used my favorite method of gravity bleeding.  (I know many say it doesn't work, but it has for me - twice now on the Vette and once on my Dakota).  Finished up that job, topped off the M/C, and first gingerly tested the pedal for hardness (it was) and then hit it hard a few times, engine off.  Turned on the key and the light's out!  And the light is working when I pull up the p-brake handle.  Sweet - ready to drive.  Gotta call my insurance guy tomorrow to put liability back on.   

Thanks for the help on this one, all.  I appreciate the input.  




 

1976 Silver/Firethorn.  L48, 4spd.  Original 2 bolt, vortec heads, 9.4:1 CR, Speed Pro Cam: 224/224@0.050, 112 LSA, Eagle Steel Crank.

Re: Proportioning valve issue

Posted: 5/31/13 5:57am Message 9 of 9
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Duncanville, TX - USA
Joined: 11/8/2003
Posts: 20218
Vette(s): #1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/ Am-Fm/map light National/Regional/Chapter NCRS "Top Flight" #2-1985 Bright Red/Carmine Cp.L-98/auto Member: NCRS, NCRS Texas, Corvette Legends of Texas
YEA!!! Clap 


Joel Adams
C3VR Lifetime Member #56    

My Link


(click for Texas-sized view!)
             NCRS

"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"

in Forum: C3 Handling Components


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