My proportioning valve switch is bad. - The 1947 - Present Chevrolet & GMC Truck Message Board Network

chevydog66 · 03-10-2006, 03:59 PM

My mechanic bled my brakes, after I had replace the rear wheel cylinder, rear flex line, and installed new rotors, calipers, pads, and braided front brake lines, and he told me that the proportioning valve switch is bad. I guess they read it with an Ohmmeter. Does anyone know where I can get just the switch? If not I will have to get a new proportioning valve. Which means I will have to bleed the brakes again. Thanks!!

krue · 03-10-2006, 05:09 PM

I wasn't aware of anything electrical on it. Sound like you need the proportioning valve. Be aware that the 73 and up valves are the same (just an extra line to plug).

CochinoFilipino · 03-10-2006, 06:12 PM

Quote:

Originally Posted by chevydog66

he told me that the proportioning valve switch is bad. I guess they read it with an Ohmmeter.

If this is right, I'm going to learn something new from this thread. bump.

Longhorn Man · 03-10-2006, 06:28 PM

there is a switch in there for the light.

cdowns · 03-10-2006, 07:21 PM

a part like that i'd go to NAPA and talk to an old guy who knows how to read the books(made out of paper)

chevydog66 · 03-10-2006, 09:46 PM

Oh ya, my truck is a 72 GMC 1500 2wd. The mechanic that worked on it told me that the switch was bad. So that's what I'm saying. I didn't know that there was a switch in there either. He bled the brakes and said that there are no leaks. But, the light is still on. He didn't say anything about the reset button on the front of the prop. valve, though. I will check NAPA tomorrow. Thanks!!

Longhorn Man · 03-10-2006, 10:21 PM

Wait a min.... before you go doing all that.
Go outside, and stomp on the brake pedal like you're about to drive off into the grand canyon. The panic stop of panic stops. You don't need to be driving it... just stomp on the pedal with all you got.
Now fire it up and see if the light is still on.

chevydog66 · 03-10-2006, 10:32 PM

OK, I'll try the "stomp the brake pedal" trick tomorrow. The truck was sitting around outside for a few years before I purchased it. And has been sitting in storage for 2 years until just a few weeks ago.

avejoe · 03-10-2006, 10:44 PM

Been through all of this.

Did you change the master cyl? The prop valves are very simple. Not much to go wrong w/them.

I finally installed a dual diaphram booster and that did the trick.

chevydog66 · 03-10-2006, 10:48 PM

I installed a new Master cyl. on it over 2 years ago. And put about 800 miles on it and then put the truck in storage for almost 2 years.

avejoe · 03-11-2006, 04:20 PM

Have the brakes worked well since you changed the master cyl?

If they have not, go get a dual diaphram booster.

Longhorn Man · 03-14-2006, 12:18 AM

Did you do the stop trick?
Did it work?

67chevemall · 03-14-2006, 11:28 AM

man I was going to toss a brand new 78 port valve but now I'll keep it and plug the extra hole......good call...

chevydog66 · 03-14-2006, 03:58 PM

I tried the stomp on it trick with no luck. The brake light is still on and there are no leaks. The brakes worked fine and the light was off until the rear wheel cylinder started leaking. But I have replaced both wheel cylinders, the rear flex line, and new rotors, calipers, pads, bearings, and new braided front flex hoses. I installed a new M/C 2 years ago and everything worked fine.

LONGHAIR · 03-14-2006, 08:36 PM

If the problem was on the rear brakes you need to open a bleeder on the front brakes and push the pedal until it reaches the end of it's travel.........it will "Pop" and the light will go out. Tighten the bleeder and release the pedal. This should cure it, but it may happen again, upon pumping the brakes. Do the same to fix it.

The real problem is that you have un-balanced pressures between the front and rear. You must relieve some of the front's pressure to even it out. That valve it just there to keep the balance and cut-off one end or the other in the event of a leak.

03-10-2006, 03:59 PM	#1
chevydog66 GM ONLY BABY!!! Join Date: Oct 2003 Location: Fort Wayne, IN. Posts: 1,998	My proportioning valve switch is bad. My mechanic bled my brakes, after I had replace the rear wheel cylinder, rear flex line, and installed new rotors, calipers, pads, and braided front brake lines, and he told me that the proportioning valve switch is bad. I guess they read it with an Ohmmeter. Does anyone know where I can get just the switch? If not I will have to get a new proportioning valve. Which means I will have to bleed the brakes again. Thanks!! __________________ 2 wrongs don't make a right, but 3 lefts do. 66 Chevelle Malibu 406ci, 573hp, 10.99@121mph 96 Chevy Silverado Z71 72 GMC 1500 Super Custom LS 6.0/4L65 on airride http://www.cardomain.com/ride/707879...mc-c-k-pick-up

03-10-2006, 05:09 PM	#2
krue Designated A-hole! Join Date: Mar 2003 Location: South Mississippi Posts: 36,448	Re: My proportioning valve switch is bad. I wasn't aware of anything electrical on it. Sound like you need the proportioning valve. Be aware that the 73 and up valves are the same (just an extra line to plug). __________________ "If it ain't broke, fix it 'til it is!" Being stupid ain't illegal. We're Still Debt Free Except for the House!!! www.daveramsey.com 70 GMC SWB Stepside project "Green Booger" soon to be 6.0l/4l80e 93 S-10 "Poppaw's Truck"

03-10-2006, 06:28 PM	#4
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,690	Re: My proportioning valve switch is bad. there is a switch in there for the light.

03-10-2006, 07:21 PM	#5
cdowns Senior Member Join Date: Jan 2003 Location: daytonabeach Posts: 22,956	Re: My proportioning valve switch is bad. a part like that i'd go to NAPA and talk to an old guy who knows how to read the books(made out of paper) __________________ 71c-10 350/2004r/4:11 lowered3/4 longbed/dead by hurricane MEANING OF DEATH::::: SOMEBODY ELSE GETS YOUR STUFF DONT BELIEVE EVERYTHING YOU THINK TAKE MY ADVISE;I DON'T USE IT ANYWAY

03-10-2006, 09:46 PM	#6
chevydog66 GM ONLY BABY!!! Join Date: Oct 2003 Location: Fort Wayne, IN. Posts: 1,998	Re: My proportioning valve switch is bad. Oh ya, my truck is a 72 GMC 1500 2wd. The mechanic that worked on it told me that the switch was bad. So that's what I'm saying. I didn't know that there was a switch in there either. He bled the brakes and said that there are no leaks. But, the light is still on. He didn't say anything about the reset button on the front of the prop. valve, though. I will check NAPA tomorrow. Thanks!! __________________ 2 wrongs don't make a right, but 3 lefts do. 66 Chevelle Malibu 406ci, 573hp, 10.99@121mph 96 Chevy Silverado Z71 72 GMC 1500 Super Custom LS 6.0/4L65 on airride http://www.cardomain.com/ride/707879...mc-c-k-pick-up

03-10-2006, 10:21 PM	#7
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,690	Re: My proportioning valve switch is bad. Wait a min.... before you go doing all that. Go outside, and stomp on the brake pedal like you're about to drive off into the grand canyon. The panic stop of panic stops. You don't need to be driving it... just stomp on the pedal with all you got. Now fire it up and see if the light is still on.

03-10-2006, 10:32 PM	#8
chevydog66 GM ONLY BABY!!! Join Date: Oct 2003 Location: Fort Wayne, IN. Posts: 1,998	Re: My proportioning valve switch is bad. OK, I'll try the "stomp the brake pedal" trick tomorrow. The truck was sitting around outside for a few years before I purchased it. And has been sitting in storage for 2 years until just a few weeks ago. __________________ 2 wrongs don't make a right, but 3 lefts do. 66 Chevelle Malibu 406ci, 573hp, 10.99@121mph 96 Chevy Silverado Z71 72 GMC 1500 Super Custom LS 6.0/4L65 on airride http://www.cardomain.com/ride/707879...mc-c-k-pick-up Last edited by chevydog66; 03-10-2006 at 10:34 PM.

03-10-2006, 10:44 PM	#9
avejoe Custer had a plan too. Join Date: Dec 2003 Location: No. California Posts: 344	Re: My proportioning valve switch is bad. Been through all of this. Did you change the master cyl? The prop valves are very simple. Not much to go wrong w/them. I finally installed a dual diaphram booster and that did the trick. __________________ 72 K15 GMC (aka Big White) Performance Rockers, Cab Corners, and Floors Fossil Fuel Glutton Neighborhood Nuisance 98 BMW 540i for Speed (Sold ) 05 Subaru Outback for mileage

03-10-2006, 10:48 PM	#10
chevydog66 GM ONLY BABY!!! Join Date: Oct 2003 Location: Fort Wayne, IN. Posts: 1,998	Re: My proportioning valve switch is bad. I installed a new Master cyl. on it over 2 years ago. And put about 800 miles on it and then put the truck in storage for almost 2 years. __________________ 2 wrongs don't make a right, but 3 lefts do. 66 Chevelle Malibu 406ci, 573hp, 10.99@121mph 96 Chevy Silverado Z71 72 GMC 1500 Super Custom LS 6.0/4L65 on airride http://www.cardomain.com/ride/707879...mc-c-k-pick-up

03-11-2006, 04:20 PM	#11
avejoe Custer had a plan too. Join Date: Dec 2003 Location: No. California Posts: 344	Re: My proportioning valve switch is bad. Have the brakes worked well since you changed the master cyl? If they have not, go get a dual diaphram booster. __________________ 72 K15 GMC (aka Big White) Performance Rockers, Cab Corners, and Floors Fossil Fuel Glutton Neighborhood Nuisance 98 BMW 540i for Speed (Sold ) 05 Subaru Outback for mileage

03-14-2006, 12:18 AM	#12
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,690	Re: My proportioning valve switch is bad. Did you do the stop trick? Did it work?

03-14-2006, 11:28 AM	#13
67chevemall Registered User Join Date: Apr 2003 Location: NB Posts: 3,367	Re: My proportioning valve switch is bad. man I was going to toss a brand new 78 port valve but now I'll keep it and plug the extra hole......good call... __________________ 1968 Chevy C10 307 3ott fleetside 1967 Chevy C/10 V8, 3spd, fleetside lwb.Sold 1967 Chev C/10 step, 383, M21. SOLD

03-14-2006, 03:58 PM	#14
chevydog66 GM ONLY BABY!!! Join Date: Oct 2003 Location: Fort Wayne, IN. Posts: 1,998	Re: My proportioning valve switch is bad. I tried the stomp on it trick with no luck. The brake light is still on and there are no leaks. The brakes worked fine and the light was off until the rear wheel cylinder started leaking. But I have replaced both wheel cylinders, the rear flex line, and new rotors, calipers, pads, bearings, and new braided front flex hoses. I installed a new M/C 2 years ago and everything worked fine. __________________ 2 wrongs don't make a right, but 3 lefts do. 66 Chevelle Malibu 406ci, 573hp, 10.99@121mph 96 Chevy Silverado Z71 72 GMC 1500 Super Custom LS 6.0/4L65 on airride http://www.cardomain.com/ride/707879...mc-c-k-pick-up Last edited by chevydog66; 03-14-2006 at 04:00 PM.

03-14-2006, 08:36 PM	#15
LONGHAIR just can't cover up my redneck Join Date: May 2004 Location: Columbus OH Posts: 11,414	Re: My proportioning valve switch is bad. If the problem was on the rear brakes you need to open a bleeder on the front brakes and push the pedal until it reaches the end of it's travel.........it will "Pop" and the light will go out. Tighten the bleeder and release the pedal. This should cure it, but it may happen again, upon pumping the brakes. Do the same to fix it. The real problem is that you have un-balanced pressures between the front and rear. You must relieve some of the front's pressure to even it out. That valve it just there to keep the balance and cut-off one end or the other in the event of a leak.



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