Thread: how to reset brake light valve
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01-23-2006 02:24 PM #1
how to reset brake light valve
I recently put an 10PSI RPV in the brake line coming off the master cyl, going into the brake light valve/ switch due to complications on using a disc/ drum master on a drum/drum system ( front brakes ither didn't work or came on after rears ), and my brake light was on, probably because of this, and it is still on, I know how the switch works, with the preassure needing to be equal otherwise the side with more preassure will overcome the side with less preassure forcing the ramp on the switch prod, closing the circut. How do I center the switch?You don't know what you've got til it's gone
Matt's 1951 Chevy Fleetline- Driver
1967 Ford Falcon- Sold
1930's styled hand built ratrod project
1974 Volkswagen Super Beetle Wolfsburg Edition- sold
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01-23-2006 04:43 PM #2
Originally posted by DennyW
Are you talking about a proportioning valve ? The type where if a line breaks, the valve moves to close that off, so you will still have brakes to get to the repair shop ?
If you are, you center it by opening the oposite bleeder, and that will allow it to move back to the center position, and put the light out.You don't know what you've got til it's gone
Matt's 1951 Chevy Fleetline- Driver
1967 Ford Falcon- Sold
1930's styled hand built ratrod project
1974 Volkswagen Super Beetle Wolfsburg Edition- sold
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01-23-2006 04:49 PM #3
Re: how to reset brake light valve
Originally posted by Matt167
I recently put an 10PSI RPV in the brake line coming off the master cyl, going into the brake light valve/ switch due to complications on using a disc/ drum master on a drum/drum system ( front brakes ither didn't work or came on after rears ), and my brake light was on, probably because of this, and it is still on, I know how the switch works, with the preassure needing to be equal otherwise the side with more preassure will overcome the side with less preassure forcing the ramp on the switch prod, closing the circut. How do I center the switch?Mike
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01-23-2006 05:01 PM #4
sounds good, thanks guys, I think it's the rears, I bled the fronts and wasn't getting any signs of fluid restriction at the bleeder. I'll probably do this tomorrow night.You don't know what you've got til it's gone
Matt's 1951 Chevy Fleetline- Driver
1967 Ford Falcon- Sold
1930's styled hand built ratrod project
1974 Volkswagen Super Beetle Wolfsburg Edition- sold
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01-23-2006 05:16 PM #5
Using a disc/drum master cylinder on a drum/drum system is dangerous. The disc side moves more fluid volume than is needed to properly activate the drums.....regardless of the residual valve. This may be why you get the unbalance signal
From the 911Brakes web site:
MASTER TYPE DESCRIPTION
DRUM / DRUM A drum / drum master is designed to deliver fluid pressure and volume to the front and the rear of a braking system in equal proportions. Drum brakes will require less fluid and pressure than disc brakes. Typically a drum brake master will be smaller than a disc master and the fluid reservoir chambers will be equal in size. Since drum brakes require the use of residual pressure valves the original drum master cylinders had residual valves built into the outlets. Later model aftermarket units do not have these valves and they must be installed in the lines externally. Failure to incorporate residual valves will cause spongy brakes.
Generally speaking it's not a good idea to use a drum brake master for disc brakes since the amount of fluid the cylinder pushes will not be sufficient.
DISC / DRUM A disc / drum master is designed to push more fluid volume to the front disc brakes since disc brakes require more volume than drum brakes. Generally speaking a disc / drum master will have one fluid reservoir larger than the other.This is because the disc brake pads wear faster than the drum shoes and the fluid reservoir will drop faster. Original disc / drum masters had a built in residual pressure valve to the rear drum brakes only.
Never reverse the outlets on a disc / drum master. Doing this will cause the front disc brakes to drag excessively from the residual pressure valve.
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01-23-2006 05:38 PM #6
Originally posted by robot
Using a disc/drum master cylinder on a drum/drum system is dangerous. The disc side moves more fluid volume than is needed to properly activate the drums.....regardless of the residual valve. This may be why you get the unbalance signal
From the 911Brakes web site:
MASTER TYPE DESCRIPTION
DRUM / DRUM A drum / drum master is designed to deliver fluid pressure and volume to the front and the rear of a braking system in equal proportions. Drum brakes will require less fluid and pressure than disc brakes. Typically a drum brake master will be smaller than a disc master and the fluid reservoir chambers will be equal in size. Since drum brakes require the use of residual pressure valves the original drum master cylinders had residual valves built into the outlets. Later model aftermarket units do not have these valves and they must be installed in the lines externally. Failure to incorporate residual valves will cause spongy brakes.
Generally speaking it's not a good idea to use a drum brake master for disc brakes since the amount of fluid the cylinder pushes will not be sufficient.
DISC / DRUM A disc / drum master is designed to push more fluid volume to the front disc brakes since disc brakes require more volume than drum brakes. Generally speaking a disc / drum master will have one fluid reservoir larger than the other.This is because the disc brake pads wear faster than the drum shoes and the fluid reservoir will drop faster. Original disc / drum masters had a built in residual pressure valve to the rear drum brakes only.
Never reverse the outlets on a disc / drum master. Doing this will cause the front disc brakes to drag excessively from the residual pressure valve.Last edited by Matt167; 01-23-2006 at 05:43 PM.
You don't know what you've got til it's gone
Matt's 1951 Chevy Fleetline- Driver
1967 Ford Falcon- Sold
1930's styled hand built ratrod project
1974 Volkswagen Super Beetle Wolfsburg Edition- sold
I wanted to complain about this NZ slang business, but I see it was resolved before it mattered. LOL..
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