Brake Warning Switch - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Legolas894 · 05-24-2012, 10:03 PM

Brakes seemed to take a long of effort to stop on my '67 GMC with front and rear drums. Thought they just needed adjustment but I looked in the master cylinder and the front reservoir was empty! Found that I had a broken brake line just after the brake hose on the left front.

I was a little concerned that the warning light didn't come on. The light does come on when the truck starts but is there a replacement switch at the M/C or way to test it to see if it's working? Shouldn't it go off if the front reservoir is empty or does it only go out if it's all empty?

Thanks

**70cst** · 05-24-2012, 11:50 PM

ttt

**Daddy Brim** · 05-25-2012, 09:40 AM

I also had a line failure on the same wheel. My light did come on, but only when the peddle was pushed firmly to the floor. Which makes no scene to me because by that time I knew I had a problem. I do not know if you can replace the switch, but if needed I would check your local parts store. I think the light is switch on the ground , constant power to the light bulb. So if you connect ground to the wire at the M.C. switch the light should come on. If it does not come on you have a problem with your wire.

Legolas894 · 05-25-2012, 06:02 PM

Thanks for the reply. I'll check that. Got to get a long piece of brake line from the MC to the left front.

Legolas894 · 05-25-2012, 10:47 PM

OK-replaced the brake line. Filled the front reservoir back up. No pedal-right to the floor without resistance. I know there's air but normally you have some feel of resistance. Is there something I need to do to the master cylinder?

**Daddy Brim** · 05-26-2012, 09:53 AM

You need to bench bleed the MC. You do not need to take it off, just put rags all around.

Legolas894 · 05-26-2012, 10:41 PM

Quote:

Originally Posted by Daddy Brim

You need to bench bleed the MC. You do not need to take it off, just put rags all around.

Thanks for the reply. Will try that. Having a hard time getting the bleeders off the front wheel cylinder. I've got new ones to put on.

05-24-2012, 10:03 PM	#1
Legolas894 Chemist under the hood... Join Date: Apr 2009 Location: Fort Erie,ON, Canada Posts: 617	Brake Warning Switch Brakes seemed to take a long of effort to stop on my '67 GMC with front and rear drums. Thought they just needed adjustment but I looked in the master cylinder and the front reservoir was empty! Found that I had a broken brake line just after the brake hose on the left front. I was a little concerned that the warning light didn't come on. The light does come on when the truck starts but is there a replacement switch at the M/C or way to test it to see if it's working? Shouldn't it go off if the front reservoir is empty or does it only go out if it's all empty? Thanks __________________ Current fleet: 2013 GMC Sierra, 5.3L, 4x4 1988 GMC Sierra, 305, Auto 1984 Jeep Grand Wagoneer, 360 V8 1997 VW Cabrio, 2.0L 2017 Toyota Rav4, 2.5L Stuff I wish I still had: 2013 Toyota Matrix [RIP] 1967 GMC 910 Fleetside, 283 V8 [1st Love-SOLD] 1987 Jeep Cherokee Laredo 4X4, 4.0 I-6 [SOLD} 1994 Chevrolet Caprice Classic, 5.7LV8 [SOLD] 1995 Chevrolet Astro AWD, 4.3L V6 (RIP) 1998 Chevrolet Suburban 4x4, 5.7L V8 [SOLD]

05-24-2012, 11:50 PM	#2
70cst Senior Member Join Date: Feb 2001 Location: New Madison, Ohio Posts: 21,373	Re: Brake Warning Switch ttt __________________ A husband can be right...or...A husband can be happy. 67-72 Chevy and GMC Trucks...The Classic Truck for the Classic Folk. 1970 CST Two tone green, 402BB, 400 Automatic, Tach, Buckets, AC, AM-FM, Tilt, GM CB, GM 8 Tract, LWB, etc JOHN 17:3...The better side of "LIFE" Remember: Everyday is a good day...Some are just gooder!

05-25-2012, 09:40 AM	#3
Daddy Brim Senior Member Join Date: Feb 2011 Location: Clovis Ca. Posts: 632	Re: Brake Warning Switch I also had a line failure on the same wheel. My light did come on, but only when the peddle was pushed firmly to the floor. Which makes no scene to me because by that time I knew I had a problem. I do not know if you can replace the switch, but if needed I would check your local parts store. I think the light is switch on the ground , constant power to the light bulb. So if you connect ground to the wire at the M.C. switch the light should come on. If it does not come on you have a problem with your wire. __________________ I'm sorry I called you stupid. I thought you knew already. 67 C-20 Custom Camper 68 Nova 396 it does wheelies 2005 Buick Century the one the wife drives 1989 Toyota Tercel to drive when I can't put gas in the first 2.

05-25-2012, 06:02 PM	#4
Legolas894 Chemist under the hood... Join Date: Apr 2009 Location: Fort Erie,ON, Canada Posts: 617	Re: Brake Warning Switch Thanks for the reply. I'll check that. Got to get a long piece of brake line from the MC to the left front. __________________ Current fleet: 2013 GMC Sierra, 5.3L, 4x4 1988 GMC Sierra, 305, Auto 1984 Jeep Grand Wagoneer, 360 V8 1997 VW Cabrio, 2.0L 2017 Toyota Rav4, 2.5L Stuff I wish I still had: 2013 Toyota Matrix [RIP] 1967 GMC 910 Fleetside, 283 V8 [1st Love-SOLD] 1987 Jeep Cherokee Laredo 4X4, 4.0 I-6 [SOLD} 1994 Chevrolet Caprice Classic, 5.7LV8 [SOLD] 1995 Chevrolet Astro AWD, 4.3L V6 (RIP) 1998 Chevrolet Suburban 4x4, 5.7L V8 [SOLD]

05-25-2012, 10:47 PM	#5
Legolas894 Chemist under the hood... Join Date: Apr 2009 Location: Fort Erie,ON, Canada Posts: 617	Re: Brake Warning Switch OK-replaced the brake line. Filled the front reservoir back up. No pedal-right to the floor without resistance. I know there's air but normally you have some feel of resistance. Is there something I need to do to the master cylinder? __________________ Current fleet: 2013 GMC Sierra, 5.3L, 4x4 1988 GMC Sierra, 305, Auto 1984 Jeep Grand Wagoneer, 360 V8 1997 VW Cabrio, 2.0L 2017 Toyota Rav4, 2.5L Stuff I wish I still had: 2013 Toyota Matrix [RIP] 1967 GMC 910 Fleetside, 283 V8 [1st Love-SOLD] 1987 Jeep Cherokee Laredo 4X4, 4.0 I-6 [SOLD} 1994 Chevrolet Caprice Classic, 5.7LV8 [SOLD] 1995 Chevrolet Astro AWD, 4.3L V6 (RIP) 1998 Chevrolet Suburban 4x4, 5.7L V8 [SOLD]

05-26-2012, 09:53 AM	#6
Daddy Brim Senior Member Join Date: Feb 2011 Location: Clovis Ca. Posts: 632	Re: Brake Warning Switch You need to bench bleed the MC. You do not need to take it off, just put rags all around. __________________ I'm sorry I called you stupid. I thought you knew already. 67 C-20 Custom Camper 68 Nova 396 it does wheelies 2005 Buick Century the one the wife drives 1989 Toyota Tercel to drive when I can't put gas in the first 2.



Register or Log In To remove these advertisements.

Register or Log In To remove these advertisements.