Master Cylinder?

Dublin · 07-08-2009, 11:47 PM

Ok, 2000 GMC Envoy 4.3 front and rear disk abs with new rotors calipers and pads 5,000 miles ago. Sudden problem braking - soft pedal with long travel almost to the floor and abs/p brake light on. Checked the fluid level - Zero, zip, nada this is not good. Checked brake lines, calipers, master,abs and everywhere no leaks hmmmm. Filled the master still soft, lights still on - air in the lines/master for sure. I'm sure I could try bleeding the master and then the system, but what's the point I know the fluid went somewhere. What do you guys think, I'd put 10 to 1 odds on a bad Master Cylinder. Also what years, models would work. Thanks

blindbatts · 07-09-2009, 02:48 PM

if the master is empty and you can't find the fluid, it's probably inside of the brake booster, meaning the m/c is bad and the brake booster will go next because the brake fluid is corrosive.

Dublin · 07-10-2009, 03:14 PM

Ok got the master cylinder and booster replaced and started to bleed the brakes. When I got to the second one, just as I tightened the blleeder...whoosh a face full of fluid. One of the lines running across the frame rail split and the others don't look so good either. A couple questions... 1st can a brake line be spliced (the originals run the length of the frame rail). 2nd how do you go about centering the valve for the abs (there are 2 what look like bleeders on each end with 3/4 wrench size) picture attached. Thanks

lee-mill · 07-10-2009, 03:19 PM

for splicing a line i wouldnt, i why not just run new lines? if it went bad in one spot chances are itll go bad in another spot. not to mention brakes are something that you shouldnt mess with lol

Dublin · 07-10-2009, 06:44 PM

Ya, it should be replaced. The thing is it runs continuos from the abs to the rear center brake hose and mostly in between the body and frame rail. There's about an inch of room to work with except where the break is. Guess this one goes to the stealership, cause it's probable that i'll damage the adjacent lines.

07-08-2009, 11:47 PM	#1
Dublin Registered User Age: 52 Join Date: Mar 2008 Posts: 18 Location: User is: OffLine	Master Cylinder? Ok, 2000 GMC Envoy 4.3 front and rear disk abs with new rotors calipers and pads 5,000 miles ago. Sudden problem braking - soft pedal with long travel almost to the floor and abs/p brake light on. Checked the fluid level - Zero, zip, nada this is not good. Checked brake lines, calipers, master,abs and everywhere no leaks hmmmm. Filled the master still soft, lights still on - air in the lines/master for sure. I'm sure I could try bleeding the master and then the system, but what's the point I know the fluid went somewhere. What do you guys think, I'd put 10 to 1 odds on a bad Master Cylinder. Also what years, models would work. Thanks
	[Reply w/Quote]

07-09-2009, 02:48 PM	#2
blindbatts Registered User Age: 27 Join Date: May 2007 Posts: 32 Location: User is: OffLine	Re: Master Cylinder? if the master is empty and you can't find the fluid, it's probably inside of the brake booster, meaning the m/c is bad and the brake booster will go next because the brake fluid is corrosive.
	[Reply w/Quote]

07-10-2009, 03:14 PM	#3
Dublin Registered User Age: 52 Join Date: Mar 2008 Posts: 18 Location: User is: OffLine	Re: Master Cylinder? Ok got the master cylinder and booster replaced and started to bleed the brakes. When I got to the second one, just as I tightened the blleeder...whoosh a face full of fluid. One of the lines running across the frame rail split and the others don't look so good either. A couple questions... 1st can a brake line be spliced (the originals run the length of the frame rail). 2nd how do you go about centering the valve for the abs (there are 2 what look like bleeders on each end with 3/4 wrench size) picture attached. Thanks
	[Reply w/Quote]

07-10-2009, 03:19 PM	#4
lee-mill where's my chippy? Age: 20 Join Date: Jun 2007 Posts: 7,846 Location: staatsburg, ny User is: OffLine	Re: Master Cylinder? for splicing a line i wouldnt, i why not just run new lines? if it went bad in one spot chances are itll go bad in another spot. not to mention brakes are something that you shouldnt mess with lol
	[Reply w/Quote]

07-10-2009, 06:44 PM	#5
Dublin Registered User Age: 52 Join Date: Mar 2008 Posts: 18 Location: User is: OffLine	Re: Master Cylinder? Ya, it should be replaced. The thing is it runs continuos from the abs to the rear center brake hose and mostly in between the body and frame rail. There's about an inch of room to work with except where the break is. Guess this one goes to the stealership, cause it's probable that i'll damage the adjacent lines.
	[Reply w/Quote]