'72 2wd Blazer brake issue - The 1947 - Present Chevrolet & GMC Truck Message Board Network

jda1a · 01-24-2010, 01:41 PM

My '72 2wd Blazer brake warning light came on last night. Checked master cylinder, rear resevoir empty. Checked under truck no leaks at wheels. Bad master cylinder, or something else? Truck has dual master cylinder power brakes with front discs. Thanks for any help.

umwtnt · 01-24-2010, 01:46 PM

When was the last time you checked the fluid level? The rear reservoir is normally for the front disc brakes. As the pads wear out the fluid level goes down to compensate for the wear. My first though is to pull the front wheels and check the pads and look for leaks on the calipers. Good Luck.

PHAT TONY · 01-24-2010, 01:54 PM

X2 on the pads; that's a big caliper to fill.

Longhorn Man · 01-24-2010, 02:30 PM

Even if the pads are worn to the steel plate, that would not drain the master cylinder.
Inspect the system for a leak. Look on the back side of the rear wheels, if the ntires are soaked with some kinda oily lookin fluid, that's the brake fluid.
if no leaks are found anywhere, then the master cylinder has a leaking seal, and it is going into the booster. Time for a new master cylinder. (very cheap at any parts house) If you have the money, it'd be good idea to do the booster too. The brake fluid will eat the rubber and pop the diaphram in there. It may not be next week, maybe not even next year... but it WILL happen.

jda1a · 01-24-2010, 05:59 PM

I think you may be right about the master cylinder and booster. I checked all four tires / wheels , found no leakage. Pulled the front wheels, still have 3/8" of pad left and no signs of a leak, Filled the rear resevoir with fresh fluid then pumped the brake pedal several times and the light went out. Will drive and re-check. Thanks to all .

01-24-2010, 01:41 PM	#1
jda1a Registered User Join Date: Jan 2007 Location: florida Posts: 3	'72 2wd Blazer brake issue My '72 2wd Blazer brake warning light came on last night. Checked master cylinder, rear resevoir empty. Checked under truck no leaks at wheels. Bad master cylinder, or something else? Truck has dual master cylinder power brakes with front discs. Thanks for any help.

01-24-2010, 01:46 PM	#2
umwtnt Registered User Join Date: Feb 2008 Location: Williamsburg, Va Posts: 226	Re: '72 2wd Blazer brake issue When was the last time you checked the fluid level? The rear reservoir is normally for the front disc brakes. As the pads wear out the fluid level goes down to compensate for the wear. My first though is to pull the front wheels and check the pads and look for leaks on the calipers. Good Luck. __________________ The more I learn, the more I find out I don't know. 69 Chevy SWB w/67 front end 4 wheel discs 468 BB 700R4 Bagged Coming around slowly

01-24-2010, 01:54 PM	#3
PHAT TONY Registered User Join Date: Aug 2008 Location: Red Deer ab canada Posts: 1,250	Re: '72 2wd Blazer brake issue X2 on the pads; that's a big caliper to fill. __________________ 1972 factory 2 Wheel Drive Blazer-Sold 1972 K10 4X4-Sold 1971 Chevrolet Cheyenne/10-Sold 1970 Chevrolet C/10-Sold 1968 GMC 4X4-Project 1968 Chevrolet C/10 Pro Street 1970 GMC 3/4 Ton-Parts 1997 2WD 2DR Yukon-Sweet http://67-72chevytrucks.com/vboard/s...d.php?t=335664

01-24-2010, 02:30 PM	#4
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	Re: '72 2wd Blazer brake issue Even if the pads are worn to the steel plate, that would not drain the master cylinder. Inspect the system for a leak. Look on the back side of the rear wheels, if the ntires are soaked with some kinda oily lookin fluid, that's the brake fluid. if no leaks are found anywhere, then the master cylinder has a leaking seal, and it is going into the booster. Time for a new master cylinder. (very cheap at any parts house) If you have the money, it'd be good idea to do the booster too. The brake fluid will eat the rubber and pop the diaphram in there. It may not be next week, maybe not even next year... but it WILL happen.

01-24-2010, 05:59 PM	#5
jda1a Registered User Join Date: Jan 2007 Location: florida Posts: 3	Re: '72 2wd Blazer brake issue I think you may be right about the master cylinder and booster. I checked all four tires / wheels , found no leakage. Pulled the front wheels, still have 3/8" of pad left and no signs of a leak, Filled the rear resevoir with fresh fluid then pumped the brake pedal several times and the light went out. Will drive and re-check. Thanks to all .



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