Brakes leaking...AGAIN. - The 1947 - Present Chevrolet & GMC Truck Message Board Network

**COBALT** · 07-31-2007, 12:30 AM

This time my master cylinder is seeping, or what appears to be a leak at the base of the master cylinder where it mounts to the brake booster. I found it while pulling my spark plugs for a tune-up, and my arm came away with brake fluid on it from the booster. It's running down, and collecting at the base of the booster.

What's frustrating is that the whole master cylinder and booster are about a year old. I rebuilt the back brakes myself, but I had a shop do this because I didn't have the time.

So...do I need to empty out my lines, the master cylinder, clean everything, and reseal, or can I somehow fix this with brake fluid in the lines? How do I bleed the whole system? Can I just do a basic brake bleed to each wheel and call it good?

**COBALT** · 08-05-2007, 01:17 PM

ttt

**70C10Toejam** · 08-05-2007, 01:49 PM

does it look like it is leaking from inside the MC? If so...I would guess a seal is leaking. Wipe it off, and press on the brakes and see if it returns. Might be time for a rebuild.

**COBALT** · 08-07-2007, 02:48 PM

I'll have to check. It is returning after a few days of driving. It just looks like the seal behind the MC is just letting fluid leak. Due to the pressures I can't imagine it getting any better. It will just leak until I loose all fluid pressure. I also noticed that the brakes aren't as crisp as they were when I rebuilt the back brakes about a year ago.

I guess my concerns are how hard it will be to get the brakes bled once I pull this apart, reseal and reassemble? I'm great with working on brakes at the wheel, but I'm worried about getting the system bled after I've removed the MC from the brake booster. I've never done it.

crazy longhorn · 08-08-2007, 10:10 AM

When you remove the lines from the master cyl, you can use vacumn caps to keep the fluid from leakin out of the lines. Be sure to bench bleed the master before you install it, & you will take care of most of the air that will be in the system. When you bleed the brakes, you can crack the rear bleeders, & let them gravity bleed 1st to get most of the air out(just be sure to keep the master full). when you dont notice any more air bubbles, tighten the bleeders, & go back in to powerbleed the system. Start @ the cyl farthest away from the master(you knew that Im sure). Dont let the master get empty.......that is where the biggest problems in bleeding come from. Best of luck,

L

07-31-2007, 12:30 AM	#1
COBALT Senior Member Join Date: Sep 2001 Location: Seattle, WA, USA Posts: 5,817	Brakes leaking...AGAIN. This time my master cylinder is seeping, or what appears to be a leak at the base of the master cylinder where it mounts to the brake booster. I found it while pulling my spark plugs for a tune-up, and my arm came away with brake fluid on it from the booster. It's running down, and collecting at the base of the booster. What's frustrating is that the whole master cylinder and booster are about a year old. I rebuilt the back brakes myself, but I had a shop do this because I didn't have the time. So...do I need to empty out my lines, the master cylinder, clean everything, and reseal, or can I somehow fix this with brake fluid in the lines? How do I bleed the whole system? Can I just do a basic brake bleed to each wheel and call it good? __________________ '69 3/4 ton C20 2wd-350ci/TH400 '69 3/4 ton Custom 20 2wd-350ci/4sp Manual '99 2wd 5.7 Chevy Tahoe Seattle, WA.

08-05-2007, 01:17 PM	#2
COBALT Senior Member Join Date: Sep 2001 Location: Seattle, WA, USA Posts: 5,817	Re: Brakes leaking...AGAIN. ttt __________________ '69 3/4 ton C20 2wd-350ci/TH400 '69 3/4 ton Custom 20 2wd-350ci/4sp Manual '99 2wd 5.7 Chevy Tahoe Seattle, WA.

08-05-2007, 01:49 PM	#3
70C10Toejam Hellasick Join Date: Jul 2006 Location: Death Moans, IA Posts: 876	Re: Brakes leaking...AGAIN. does it look like it is leaking from inside the MC? If so...I would guess a seal is leaking. Wipe it off, and press on the brakes and see if it returns. Might be time for a rebuild. __________________ I keep two MAGNUMS in my desk. One's a gun, and I keep it loaded. The other's a bottle and it keeps ME loaded. I'm Tracer Bullet. (Calvin and Hobbes) This life was a test. It was only a test. If this had been an actual life, you would have received instructions on where to go and what to do. RED meat is not bad for you...FUZZY BLUE/GREEN MEAT is bad for you!!!!!!!!!!!!! BUILT FORD TOUGH WITH CHEVY STUFF--sticker at Goodguys

08-07-2007, 02:48 PM	#4
COBALT Senior Member Join Date: Sep 2001 Location: Seattle, WA, USA Posts: 5,817	Re: Brakes leaking...AGAIN. I'll have to check. It is returning after a few days of driving. It just looks like the seal behind the MC is just letting fluid leak. Due to the pressures I can't imagine it getting any better. It will just leak until I loose all fluid pressure. I also noticed that the brakes aren't as crisp as they were when I rebuilt the back brakes about a year ago. I guess my concerns are how hard it will be to get the brakes bled once I pull this apart, reseal and reassemble? I'm great with working on brakes at the wheel, but I'm worried about getting the system bled after I've removed the MC from the brake booster. I've never done it. __________________ '69 3/4 ton C20 2wd-350ci/TH400 '69 3/4 ton Custom 20 2wd-350ci/4sp Manual '99 2wd 5.7 Chevy Tahoe Seattle, WA.

08-08-2007, 10:10 AM	#5
crazy longhorn Fabricate till you "puke" Join Date: Jun 2002 Location: Ill Posts: 9,403	Re: Brakes leaking...AGAIN. When you remove the lines from the master cyl, you can use vacumn caps to keep the fluid from leakin out of the lines. Be sure to bench bleed the master before you install it, & you will take care of most of the air that will be in the system. When you bleed the brakes, you can crack the rear bleeders, & let them gravity bleed 1st to get most of the air out(just be sure to keep the master full). when you dont notice any more air bubbles, tighten the bleeders, & go back in to powerbleed the system. Start @ the cyl farthest away from the master(you knew that Im sure). Dont let the master get empty.......that is where the biggest problems in bleeding come from. Best of luck, L __________________ 69 longhorn,4" chop,3/5 drop, 1/2 ton suspension/disc brakes,1 1/2" body drop,steel tilt clip, 5.3/Edelbrock rpm intake/600 carb, Hooker streetrod shorties,2 1/2" exhaust/ H pipe/50's Flows , 6 spd Richmond trans,12 bolt/ 3.40 gears....



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