Vac. leak...... I think - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Mike Culpepper · 04-08-2005, 09:52 AM

I think I have a power brake booster leak and have a few Q's. There is a hissing sound near the booster, and when I pinch the boosters' vac. hose with channel locks, theengine idle changes.
I was planning to replace the power booster but how do I know if the Master cylinder needs replacing also? COuld the MC and not the booster be the problem?

Can the booster be replaced without removing the MC (i.e. unbolt the MC to booster bolts and slip out the booster, or does the MC need to be disconnected from its' brake lines and removed also).

Any gaskets or seals between the MC and booster that don't usually come with a new booster?
Mike

smokekiki · 04-08-2005, 11:20 AM

Yes there is enough room to remove the mc without taking the lines off.Is the vac hose in good shape and tight?Make sure.The booster should hold vac even after the truck has been off for a while.Build some vac up and turn it off.Pull the fitting out of the booster after 5 min,see if the is any vac.

Mike Culpepper · 04-08-2005, 12:14 PM

Yea, new vac. line and on there good. I replaced it when I was looking for a reason my truck was runnung bad. Turns out engine is terminally wounded and crate engine is on it's way.
WHen you check for vac. after shutting the truck off, like you mentioned above,should you hear a sound if it's holding vac? Sucking sound when you remove the fitting?

smokekiki · 04-08-2005, 01:38 PM

Yes,You will hear a sucking sound.

blazerparts · 04-08-2005, 01:50 PM

I just replaced the master cylinder on my truck, there is a gasket between it and the booster. NAPA said they didn't have a precut gasket for it, but gave me a sheet of material to make my own.

Mike Culpepper · 04-08-2005, 03:34 PM

blazerparts/
Do you remember seeing or replacing a rubber "master cylinder push rod seal" or "cup seal" on yours? I seem to remember reading a post a few weeks ago when I first thought about changing the booster that mentioned that. Where would you get one of those if it is torn? I'm trying to anticipate things before hand.
THanks

04-08-2005, 09:52 AM	#1
Mike Culpepper Red Join Date: Feb 2003 Location: Llano... Texas Hill Country Posts: 448	Vac. leak...... I think I think I have a power brake booster leak and have a few Q's. There is a hissing sound near the booster, and when I pinch the boosters' vac. hose with channel locks, theengine idle changes. I was planning to replace the power booster but how do I know if the Master cylinder needs replacing also? COuld the MC and not the booster be the problem? Can the booster be replaced without removing the MC (i.e. unbolt the MC to booster bolts and slip out the booster, or does the MC need to be disconnected from its' brake lines and removed also). Any gaskets or seals between the MC and booster that don't usually come with a new booster? Mike __________________ '72 Cheyenne LWB 350/350 "The sun don't shine on the same dog's ass all the time." - Catfish Hunter (commenting on why he was not able to pitch another perfect game).

04-08-2005, 11:20 AM	#2
smokekiki Mike Join Date: Jan 2003 Location: west chester pa Posts: 2,473	Yes there is enough room to remove the mc without taking the lines off.Is the vac hose in good shape and tight?Make sure.The booster should hold vac even after the truck has been off for a while.Build some vac up and turn it off.Pull the fitting out of the booster after 5 min,see if the is any vac. __________________ 70'c/10, 71 suburban4x4 402bb, 72suburban 4/6 drop, 72k/5 4x4 blazer 4" lift 35 tires

04-08-2005, 12:14 PM	#3
Mike Culpepper Red Join Date: Feb 2003 Location: Llano... Texas Hill Country Posts: 448	Yea, new vac. line and on there good. I replaced it when I was looking for a reason my truck was runnung bad. Turns out engine is terminally wounded and crate engine is on it's way. WHen you check for vac. after shutting the truck off, like you mentioned above,should you hear a sound if it's holding vac? Sucking sound when you remove the fitting? __________________ '72 Cheyenne LWB 350/350 "The sun don't shine on the same dog's ass all the time." - Catfish Hunter (commenting on why he was not able to pitch another perfect game).

04-08-2005, 01:38 PM	#4
smokekiki Mike Join Date: Jan 2003 Location: west chester pa Posts: 2,473	Yes,You will hear a sucking sound. __________________ 70'c/10, 71 suburban4x4 402bb, 72suburban 4/6 drop, 72k/5 4x4 blazer 4" lift 35 tires

04-08-2005, 01:50 PM	#5
blazerparts No,I DON'T have Tourett's Join Date: Mar 2005 Location: Reno, NV Posts: 556	I just replaced the master cylinder on my truck, there is a gasket between it and the booster. NAPA said they didn't have a precut gasket for it, but gave me a sheet of material to make my own. __________________ '72 K5 CST 350/350 Daily Driver '69 GMC3500 Camper Special CST Flatbed 396/400 Upgraded to show truck '69 GMC 2500 L6292, 3spd beater

04-08-2005, 03:34 PM	#6
Mike Culpepper Red Join Date: Feb 2003 Location: Llano... Texas Hill Country Posts: 448	blazerparts/ Do you remember seeing or replacing a rubber "master cylinder push rod seal" or "cup seal" on yours? I seem to remember reading a post a few weeks ago when I first thought about changing the booster that mentioned that. Where would you get one of those if it is torn? I'm trying to anticipate things before hand. THanks __________________ '72 Cheyenne LWB 350/350 "The sun don't shine on the same dog's ass all the time." - Catfish Hunter (commenting on why he was not able to pitch another perfect game).



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