Master cylinder is leaking - The 1947 - Present Chevrolet & GMC Truck Message Board Network

70c10 · 12-23-2002, 01:41 PM

My master cylinder has been seeping fluid for over a year. Now it is leaking more. It's leaking right where it's bolted to the booster. Is the master cylinder shot or is there a gasket or seal between it and the booster that needs replacing?. Thanks

da-burb · 12-23-2002, 01:43 PM

The master cylinder is shot.

70c10 · 12-23-2002, 01:55 PM

I figured that. It looks like a new one is $40-$60. Is it pretty easy to change?. Looks like a simple bolt on.

marcuspboldt · 12-23-2002, 03:17 PM

Yes it is easy to change. Be sure to bench bleed the new unit first
(the new one should come with instructions on how to do this, and some plastic tubes and fittings) Then you need to bleed the entire system.
Good luck.

tom hand · 12-23-2002, 03:52 PM

Actually if you follow a few simple steps, bleeding the whole system is not necessary. Bench bleed the master cylinder, then install it. Now just barely move the petal, 1/16 to 1/8 of an inch. It helps if you have the hood open and the top off the master cylinder. You will be able to see all the air you introduced "burp" back up thru the master cylinder. When the bubbles quit coming up,your done. Have done hundreds this way and never had to bleed the whole system when just replacing the master cylinder.

sgtjed · 12-23-2002, 04:07 PM

wow! 40-60 for a new one? get one at autozone with a lifetime warranty for 19.99. thats what i did. sure its rebuilt but i have not had any bad luck with it.

70c10 · 12-23-2002, 05:02 PM

Thanks guys. Sounds easy enough. I guess if a rebuilt one is o.k. , I'll go with that.

12-23-2002, 01:41 PM	#1
70c10 67-72 Addict! Join Date: Feb 2002 Location: The TAX State! Posts: 7,857	Master cylinder is leaking My master cylinder has been seeping fluid for over a year. Now it is leaking more. It's leaking right where it's bolted to the booster. Is the master cylinder shot or is there a gasket or seal between it and the booster that needs replacing?. Thanks __________________ Jim 1970 C/10 Fleetside w/Ghost Flames Lowered 4.5" front and 4" rear (Raked) 355/350 Turbo w/shift kit 10" Redneck Performance Verter w/2500 stall Hooker Super Comps part#2808-1 Performer RPM Air-Gap 12 Bolt w/3:73 gears- Eaton Posi Comp Cams XE262 with 1.6 Crane Energizers, Road Demon 625 and Brodix IK 180 heads

12-23-2002, 01:43 PM	#2
da-burb "Ochre Ogre" Join Date: Apr 2000 Location: Springfield, MN Posts: 3,558	The master cylinder is shot. __________________ Bowtie Truck Stop Inc. Mid-West GM Truck Restoration Parts Supplier Your Key Parts, Auto Metal Direct, Dynacorn, and Goodmark dealer. like us @ www.facebook.com/BowtieTruckStop 1971 C-10 Suburban (Ochre) 1971 K-10 Suburban (Ochre) 1972 C-10 Suburban (Ochre) 1972 K-20 Suburban (Yellow- that just aint right!) Springfield, Minnesota 56087

12-23-2002, 01:55 PM	#3
70c10 67-72 Addict! Join Date: Feb 2002 Location: The TAX State! Posts: 7,857	I figured that. It looks like a new one is $40-$60. Is it pretty easy to change?. Looks like a simple bolt on. __________________ Jim 1970 C/10 Fleetside w/Ghost Flames Lowered 4.5" front and 4" rear (Raked) 355/350 Turbo w/shift kit 10" Redneck Performance Verter w/2500 stall Hooker Super Comps part#2808-1 Performer RPM Air-Gap 12 Bolt w/3:73 gears- Eaton Posi Comp Cams XE262 with 1.6 Crane Energizers, Road Demon 625 and Brodix IK 180 heads

12-23-2002, 03:52 PM	#5
tom hand CCRider Join Date: Feb 2000 Location: Olive Branch,MS,USA Posts: 2,232	Actually if you follow a few simple steps, bleeding the whole system is not necessary. Bench bleed the master cylinder, then install it. Now just barely move the petal, 1/16 to 1/8 of an inch. It helps if you have the hood open and the top off the master cylinder. You will be able to see all the air you introduced "burp" back up thru the master cylinder. When the bubbles quit coming up,your done. Have done hundreds this way and never had to bleed the whole system when just replacing the master cylinder. __________________ 72 GMC Sierra SWB almost finished---- 84 Softail Olive Branch MS

12-23-2002, 05:02 PM	#7
70c10 67-72 Addict! Join Date: Feb 2002 Location: The TAX State! Posts: 7,857	Thanks guys. Sounds easy enough. I guess if a rebuilt one is o.k. , I'll go with that. __________________ Jim 1970 C/10 Fleetside w/Ghost Flames Lowered 4.5" front and 4" rear (Raked) 355/350 Turbo w/shift kit 10" Redneck Performance Verter w/2500 stall Hooker Super Comps part#2808-1 Performer RPM Air-Gap 12 Bolt w/3:73 gears- Eaton Posi Comp Cams XE262 with 1.6 Crane Energizers, Road Demon 625 and Brodix IK 180 heads

12-23-2002, 03:17 PM	#4
marcuspboldt Registered Abuser Join Date: Nov 2002 Location: Ft.Worth Texas Posts: 1,001	Yes it is easy to change. Be sure to bench bleed the new unit first (the new one should come with instructions on how to do this, and some plastic tubes and fittings) Then you need to bleed the entire system. Good luck.

12-23-2002, 04:07 PM	#6
sgtjed What if? Join Date: Oct 2002 Location: Choctaw,Oklahoma Posts: 649	wow! 40-60 for a new one? get one at autozone with a lifetime warranty for 19.99. thats what i did. sure its rebuilt but i have not had any bad luck with it.



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