bleeding master cylinder - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Jeremy_5 · 03-11-2004, 05:48 PM

how do you bleed the master cylinder if its in the truck?

Gordo · 03-11-2004, 08:11 PM

Is this a new or rebuilt master just installed or has it been in operation for a while? If it's new or rebuilt, I would pull it back off and bench bleed it first. If it's been in operation already, have someone hold down the brake pedal firmly (try not to pump it) and crack open both fittings on the side of the master about 1/2 turn and when the pedal hits the floor tighten the fittings back up. Do this twice, keeping the reservoir full of course.

*67Fleetsidedream* · 03-11-2004, 08:38 PM

Start with the back brakes first and work your way forward.

Jeremy_5 · 03-12-2004, 04:04 PM

when I open up the fittings on the MC will brake fluid come out, as it does with the bleeder screws on the wheel cylnders.

BLACK AND BLUE 67-72 · 03-12-2004, 04:43 PM

Yes it will.

Jeremy_5 · 03-12-2004, 05:55 PM

Okay, I am confused, coming off the power brake booster their is the MC, but I also see a long slender peice attached to the MC, all the brake lines go to it, what is it, and that is the only bleeder screw I see, is that the one I need to bleed the MC? any body have any pics, thanks

BLACK AND BLUE 67-72 · 03-12-2004, 07:03 PM

pic

BLACK AND BLUE 67-72 · 03-12-2004, 07:04 PM

BLACK AND BLUE 67-72 · 03-12-2004, 07:16 PM

okay, the long slender thing that all of the lines go into is the proportining valve, mine does not have a bleeder on it some do, and some master cylinders do also. What gordo was referring to was the two lines that come out of the master cylinder. But if you have a prop. valve that has the bleeder on it use that, if it is a new master cylinder then usually it will come with a bleeder kit ( two fittings, two clear hoses and a clip, so you could bench bleed it while on the truck. If it doesn't have a bleeder and you don't want brake fluid then I would recomend using the wheel cylinders and bleeding it that way, and as far as starting with the furthest wheel away, I have also read in the Chevrolet Service manual to bleed it from the closest wheel first, so as not to push air into the rest of the lines.

03-11-2004, 05:48 PM	#1
Jeremy_5 Truck addict Join Date: Sep 2003 Location: Lincoln, California Posts: 497	bleeding master cylinder how do you bleed the master cylinder if its in the truck? __________________ 1956 Chevy Napco 1972 Cheyenne Super 1970 K20

03-11-2004, 08:11 PM	#2
Gordo Registered User Join Date: Jan 2001 Location: Killingworth, CT. USA Posts: 3,378	Is this a new or rebuilt master just installed or has it been in operation for a while? If it's new or rebuilt, I would pull it back off and bench bleed it first. If it's been in operation already, have someone hold down the brake pedal firmly (try not to pump it) and crack open both fittings on the side of the master about 1/2 turn and when the pedal hits the floor tighten the fittings back up. Do this twice, keeping the reservoir full of course. __________________ 1971 C10 swb stepside 350/700R4/3.73posi (retired as of 4/22/03) 1998 S10 short bed 2002 S10 Blazer 1942 Oldsmobile 1958 Massey Harris Pony 1951 Wife Killingworth, Connecticut May those who love us, love us, any of those who do not love us, may God turn their hearts. And if God is unable to turn their hearts, may he turn their ankles so we may know them by their limping. A man who works with his hands is a laborer; a man who works with his hands and his brain is a craftsman; but a man who works with his hands and his brain and his heart is an artist.

03-12-2004, 04:04 PM	#4
Jeremy_5 Truck addict Join Date: Sep 2003 Location: Lincoln, California Posts: 497	when I open up the fittings on the MC will brake fluid come out, as it does with the bleeder screws on the wheel cylnders. __________________ 1956 Chevy Napco 1972 Cheyenne Super 1970 K20

03-12-2004, 04:43 PM	#5
BLACK AND BLUE 67-72 Firefighter Join Date: Feb 2001 Location: Yellville, Ar, USA Posts: 1,943	Yes it will. __________________ '72 Chevy SWB 350 Auto '67 GMC LWB 350 4 speed '70 Chevy 4x4 Stepside 350 Auto Yellville, Ar. USA

03-12-2004, 05:55 PM	#6
Jeremy_5 Truck addict Join Date: Sep 2003 Location: Lincoln, California Posts: 497	Okay, I am confused, coming off the power brake booster their is the MC, but I also see a long slender peice attached to the MC, all the brake lines go to it, what is it, and that is the only bleeder screw I see, is that the one I need to bleed the MC? any body have any pics, thanks __________________ 1956 Chevy Napco 1972 Cheyenne Super 1970 K20

03-11-2004, 08:38 PM	#3
67Fleetsidedream Wiseass secured himself a BAN Join Date: Nov 2000 Location: MOON!!! Posts: 2,282	Start with the back brakes first and work your way forward.

03-12-2004, 07:03 PM	#7
BLACK AND BLUE 67-72 Firefighter Join Date: Feb 2001 Location: Yellville, Ar, USA Posts: 1,943	pic Attached Images __________________ '72 Chevy SWB 350 Auto '67 GMC LWB 350 4 speed '70 Chevy 4x4 Stepside 350 Auto Yellville, Ar. USA

03-12-2004, 07:04 PM	#8
BLACK AND BLUE 67-72 Firefighter Join Date: Feb 2001 Location: Yellville, Ar, USA Posts: 1,943	Attached Images __________________ '72 Chevy SWB 350 Auto '67 GMC LWB 350 4 speed '70 Chevy 4x4 Stepside 350 Auto Yellville, Ar. USA

03-12-2004, 07:16 PM	#9
BLACK AND BLUE 67-72 Firefighter Join Date: Feb 2001 Location: Yellville, Ar, USA Posts: 1,943	okay, the long slender thing that all of the lines go into is the proportining valve, mine does not have a bleeder on it some do, and some master cylinders do also. What gordo was referring to was the two lines that come out of the master cylinder. But if you have a prop. valve that has the bleeder on it use that, if it is a new master cylinder then usually it will come with a bleeder kit ( two fittings, two clear hoses and a clip, so you could bench bleed it while on the truck. If it doesn't have a bleeder and you don't want brake fluid then I would recomend using the wheel cylinders and bleeding it that way, and as far as starting with the furthest wheel away, I have also read in the Chevrolet Service manual to bleed it from the closest wheel first, so as not to push air into the rest of the lines. __________________ '72 Chevy SWB 350 Auto '67 GMC LWB 350 4 speed '70 Chevy 4x4 Stepside 350 Auto Yellville, Ar. USA

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