More vacuum leak questions - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Low68 · 01-13-2003, 03:01 PM

Hey everybody...If you remember, I asked about a vacuum leak that I had. It was suggested that I replace the vacuum check valve and the gasket. I did that, but it didn't make any difference. Is there any other gaskets that can be the cause of that? Does it sound like my booster is shot? I want to try replacing any possible gaskets before having to buy a new one. Thanks for the help.
Low68

72MARIO · 01-13-2003, 05:40 PM

I think it could be the booster they should be fairly cheep Buy a new one .

lukecp · 01-13-2003, 05:59 PM

Take the booster vaccum hose off, and plug it or pinch it shut. Drive the truck w/o power brakes (just don't go very fast) and see if you still have a vaccum leak. Another way to check the booster is to get in the truck with the engine off, pump the brake pedal 5 or 6 times until it gets really stiff. Then put your foot firmly on the brakes, and start the engine. When the engine fires the brake pedal should sink in about an inch or two if the booster is working good.

Low68 · 01-13-2003, 06:19 PM

Thanks for the help. Other suggestions are welcome also. I want to get this fixed. Thanks
Low68

ChevLoRay · 01-13-2003, 06:56 PM

Hydro-Vac's do go bad. That is the vacuum booster that you are citing. With the engine running, does it run rougher when you press the brake pedal down? Do you hear a "Hiss"? If so, the odds are that the diaphragm in the booster is leaking. You can't fix it. You will have to use it as a core to get a replacement. Good luck.

hecticblasts · 01-14-2003, 12:43 AM

If you are running an automatic with a vaccum modulator check the connection at the fitting and at the modulator for dry rot.HF

01-13-2003, 03:01 PM	#1
Low68 Registered User Join Date: May 2001 Location: Arizona Posts: 758	More vacuum leak questions Hey everybody...If you remember, I asked about a vacuum leak that I had. It was suggested that I replace the vacuum check valve and the gasket. I did that, but it didn't make any difference. Is there any other gaskets that can be the cause of that? Does it sound like my booster is shot? I want to try replacing any possible gaskets before having to buy a new one. Thanks for the help. Low68 __________________ Build Thread

01-13-2003, 05:40 PM	#2
72MARIO Registered User Join Date: Nov 2000 Location: Huntsville Ontario Canada Posts: 4,052	I think it could be the booster they should be fairly cheep Buy a new one . __________________ 1968 Suburban numbers matching all original truck now equipped with 6.0/4L80 on Accuair http://67-72chevytrucks.com/vboard/s...d.php?t=625017 1967 C/20 6.0/4L80 Roofing Truck 1990 V2500 Suburban "Plow Truck" 2005 TAHOE DD

01-13-2003, 05:59 PM	#3
lukecp Formerly yellow72custom Join Date: May 2001 Location: Austin, TX Posts: 7,531	Take the booster vaccum hose off, and plug it or pinch it shut. Drive the truck w/o power brakes (just don't go very fast) and see if you still have a vaccum leak. Another way to check the booster is to get in the truck with the engine off, pump the brake pedal 5 or 6 times until it gets really stiff. Then put your foot firmly on the brakes, and start the engine. When the engine fires the brake pedal should sink in about an inch or two if the booster is working good. __________________ '72 Chevy C10 Mild 350/TH350/3.07. Ochre/White. Old high school ride. '70 GMC C2500 '62 327 4bbl/SM465/4.56-geared Dana 60. White/White. Project or parts truck. '97 Saturn SL DD. 1.9/5-speed. 40+ highway mpg

01-13-2003, 06:19 PM	#4
Low68 Registered User Join Date: May 2001 Location: Arizona Posts: 758	Thanks for the help. Other suggestions are welcome also. I want to get this fixed. Thanks Low68 __________________ Build Thread

01-13-2003, 06:56 PM	#5
ChevLoRay Old Skool Club Join Date: Jun 2001 Location: Benton, AR "The Heart of Arkansas" Posts: 10,880	Hydro-Vac's do go bad. That is the vacuum booster that you are citing. With the engine running, does it run rougher when you press the brake pedal down? Do you hear a "Hiss"? If so, the odds are that the diaphragm in the booster is leaking. You can't fix it. You will have to use it as a core to get a replacement. Good luck. __________________ Member Nr. 2770 '96 GMC Sportside; 4.3/SLT - Daily driven....constantly needs washed. '69 C-10 SWB; 350/TH400 - in limbo The older I get, the better I was.

01-14-2003, 12:43 AM	#6
hecticblasts Registered User Join Date: Oct 2002 Location: Concord,NC Posts: 94	vac. leak If you are running an automatic with a vaccum modulator check the connection at the fitting and at the modulator for dry rot.HF



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