Resetting brake light switch
Thread Starter
Melting Slicks
Joined: Apr 2002
Posts: 2,337
Likes: 14
From: Norfolk VA
Resetting brake light switch
I had to replace the left rear brake caliper due to it leaking. I have not bled the brakes yet. Will bleed them tomorrow. My question is there another way of center the pressure differential valve to turn off the brake light without slamming on the brake pedal? I have a high lift cam with a duration of 233 intake, 241 exhaust @ .050 and the engine puts out a low vacuum signal (8" at idle) the brakes do not stop the car well prior to the caliper leaking nor do my head light doors do not open.
Last edited by Oldguard 7; May 8, 2018 at 12:29 AM.
Le Mans Master
Joined: Aug 2017
Posts: 8,336
Likes: 2,810
From: Cool Northern Michigan
Yes, you need the special little tool ($15) that keeps the Proportioning Valve piston centered. Click on my profile and check out my photo album #3. It shows a drawing of the inside of the Prop V and the tool you need, if you bleed the system using the brake pedal method.
If your "dashboard warning brake-lite" is on now, jabbing the pedal will usually reset the Prop V. switch. There is a spring in there, so it should return to neutral unless its defective.
Others have had luck by opening a bleeder screw on the opposite end of the brake system, jam the brake pedal to force the piston back to neutral.
I would highly recommend bleeding by Motive Pressure or Vacuum methods instead of using the pedal.
If your "dashboard warning brake-lite" is on now, jabbing the pedal will usually reset the Prop V. switch. There is a spring in there, so it should return to neutral unless its defective.
Others have had luck by opening a bleeder screw on the opposite end of the brake system, jam the brake pedal to force the piston back to neutral.
I would highly recommend bleeding by Motive Pressure or Vacuum methods instead of using the pedal.
Last edited by HeadsU.P.; May 8, 2018 at 07:36 AM.
Le Mans Master
Joined: Aug 2010
Posts: 5,339
Likes: 546
From: Central Texas
Yes, you need the special little tool ($15) that keeps the Proportioning Valve piston centered. Click on my profile and check out my photo album #3. It shows a drawing of the inside of the Prop V and the tool you need, if you bleed the system using the brake pedal method.
If your "dashboard warning brake-lite" is on now, jabbing the pedal will usually reset the Prop V. switch. There is a spring in there, so it should return to neutral unless its defective.
Others have had luck by opening a bleeder screw on the opposite end of the brake system, jam the brake pedal to force the piston back to neutral.
I would highly recommend bleeding by Motive Pressure or Vacuum methods instead of using the pedal.
If your "dashboard warning brake-lite" is on now, jabbing the pedal will usually reset the Prop V. switch. There is a spring in there, so it should return to neutral unless its defective.
Others have had luck by opening a bleeder screw on the opposite end of the brake system, jam the brake pedal to force the piston back to neutral.
I would highly recommend bleeding by Motive Pressure or Vacuum methods instead of using the pedal.
Is there a downside to using the tool with the Motive bleeder?
Craig
Le Mans Master
Joined: Aug 2017
Posts: 8,336
Likes: 2,810
From: Cool Northern Michigan
That little Prop V. locking tool is mostly for the brake Pedal Bleed method. It is not normally needed for:
Motive Pressure method
Vacuum method
Gravity method
Let somebody else do it method.
I read somewhere that when the brake pedal is applied, that over 400 lbs of pressure is forced on the brake system. Thats more or less what triggers the Prop V. piston over center if a leak is detected. A Motive Pres tank only applies around 10-15 lbs. It doesn't take much to get a good flow through the lines.
Motive Pressure method
Vacuum method
Gravity method
Let somebody else do it method.
I read somewhere that when the brake pedal is applied, that over 400 lbs of pressure is forced on the brake system. Thats more or less what triggers the Prop V. piston over center if a leak is detected. A Motive Pres tank only applies around 10-15 lbs. It doesn't take much to get a good flow through the lines.
Last edited by HeadsU.P.; May 8, 2018 at 09:50 AM.
Race Director
Joined: Apr 2009
Posts: 19,294
Likes: 2,754
From: Charlotte NC
Knowing that I am tool ***** and I saw this tool that you have shown us in the past. I paid attention and I went and got it for the heck of it.
But I can say...I had never needed to use it before I got it nor needed to use it since I have got it and all of the brake jobs that I have bled out that had the brake warning light on ...the light went off when the system was correctly bled. And on those brake systems that the brake light was not on..it did not come on.
I apply pressure to the brake pedal ( if needed) as if i were in a panic stop scenario. Because lets face it...the brakes have to pass that type of scenario to leave my shop.
But I got the tool due to it being inexpensive and does make sense if needed and the brake light will not seem to go off and the system is bled perfectly.
DUB
But I can say...I had never needed to use it before I got it nor needed to use it since I have got it and all of the brake jobs that I have bled out that had the brake warning light on ...the light went off when the system was correctly bled. And on those brake systems that the brake light was not on..it did not come on.
I apply pressure to the brake pedal ( if needed) as if i were in a panic stop scenario. Because lets face it...the brakes have to pass that type of scenario to leave my shop.
But I got the tool due to it being inexpensive and does make sense if needed and the brake light will not seem to go off and the system is bled perfectly.
DUB
Last edited by DUB; May 8, 2018 at 06:47 PM.
Had a 1976 L-82, 4-sp
Joined: Mar 2011
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From: Some days your the dog and some days your the hydrant.
Royal Canadian Navy
I've never had to use that tool and I do my brakes the old way with pedal pressure. Like Dub says, a hard stab of the brake will reset the valve just like GM said it would.
Thread Starter
Melting Slicks
Joined: Apr 2002
Posts: 2,337
Likes: 14
From: Norfolk VA
I have a motive pressure bleeder and will bleed the system tomorrow. I may need that tool to center the shuttle valve. The brakes did not bring the vehicle to a stop like it did prior to my cam install and the caliper was not leaking after this cam installation nor was the brake light on. The brake light came on after replacing the caliper. I also checked for vacuum leaks prior to replacing the
caliper. Im not sure if standing on the pedal will center the valve to turn off the brake light due to the low vacuum signal caused by the 233/241(not advertised) duration cam and low vacuum signal.
caliper. Im not sure if standing on the pedal will center the valve to turn off the brake light due to the low vacuum signal caused by the 233/241(not advertised) duration cam and low vacuum signal.
Last edited by Oldguard 7; May 9, 2018 at 01:18 AM.
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Had a 1976 L-82, 4-sp
Joined: Mar 2011
Posts: 5,338
Likes: 1,213
From: Some days your the dog and some days your the hydrant.
Royal Canadian Navy
