Vacuum issues - help me gents - The 1947 - Present Chevrolet & GMC Truck Message Board Network

makovai · 06-09-2006, 11:07 AM

I've got a vacuum issue that really sucks (sorry i had to open with that line)

My rig is making a loud hissing noise that is only there when i don't step on the brakes. As soon as i brake even a little bit, it goes away. I popped the hood and its pretty loud but i cant seem to find it. Does this sound like maybe i broke a diaphram in my booster? It's driving me nuts.

Burt4x4 · 06-09-2006, 11:32 AM

Could be?
What I would do is get a can of carb cleaner, fire up your rig and now spray the fluid around your booster, being careful and watch were you spray, when you hear your rpm go up you have found the vacume leak..depending on were it is will steer you to the fix

Good Luck
Burt

HuggerCST · 06-09-2006, 12:38 PM

Quote:

Originally Posted by makovai

Does this sound like maybe i broke a diaphram in my booster?

Yep, you need a new booster! You can also pinch the vac. hose to the booster with pliers while the engine is running to verify it, but I'm sure that's what it is.

Jason915 · 06-09-2006, 12:45 PM

I would isolate the problem by disconnecting the vacuum line to the booster and see if it goes away. Also a cheap vacuum gauge is very helpful.

Good luck

**JMac11** · 06-09-2006, 12:51 PM

Replaced all my vacuum lines and Booster, truck would not idle. Quit counting the turns of the idle screws at 6. Takes about 12 foot to replace all your under dash ones.

makovai · 06-09-2006, 01:08 PM

funny thing is i have a vacuum gage. Put it in couple weeks ago in the blank spot next to the oil pressure gage. It really doesn't show that im low on vacuum, although my brakes have never work very well. I wrote a thread a while back about switching to a hydraboost. I bought one but never installed it. Maybe I've have a bad booster since i bought the rig.

Beside...... brakes are overatted, all they do is slow you down.

**FRENCHBLUE72** · 06-09-2006, 03:53 PM

Sounds like now is a great time to swap to the hydro set-up..

Burt4x4 · 06-09-2006, 04:37 PM

What I did is upgrade my booster to 1ton.
1/2ton truck have a single diaphram booster were 1ton uses a double.
WOW! I can actualyl lock up my 35" swampers now. HUGE improvement.
Simply when to Autozone (they carry AC Delco) and ordered a Master/Booster set for a 1972 K30 1ton 4x4 p/u.
My brake are better than ever!
Burt

makovai · 06-10-2006, 08:27 AM

damn...i got to this post after i bought a replacement booster. That was the problem. The brakes work a little better, but the biggest thing is the vacuum leak is gone. Now i kinda wish i would have bought a 1 ton booster. I cannot nor have i ever been able to lock my brakes up.

DEFIANT NCC-74205 · 06-10-2006, 11:26 AM

I put in a 1 ton too. Got it a while back in the yard. Works good. I've considered hydro-boost, but abandoned the idea. Just more hoses to leak and when your power steering pump takes a dump you loose your brakes. Another way to decrease brake effort is to get a master cylinder with a smaller bore. That's right a smaller bore increases brake pressure and reduces effort.
Well at least you fixed your vacuum leak. Another good way to check for vacuum leaks is by squirting water. Works like a can of carb cleaner, but makes a nice slurping sound when you find the leak and it makes the engine rpm drop when sucked in.
"If at first you don't succeed, keep on sucking 'till you do succeed" - Curly Howard

06-09-2006, 11:07 AM	#1
makovai Senior Member Join Date: Feb 2006 Location: oregon city Posts: 335	Vacuum issues - help me gents I've got a vacuum issue that really sucks (sorry i had to open with that line) My rig is making a loud hissing noise that is only there when i don't step on the brakes. As soon as i brake even a little bit, it goes away. I popped the hood and its pretty loud but i cant seem to find it. Does this sound like maybe i broke a diaphram in my booster? It's driving me nuts. __________________ If it aint broke..............fix it till it is. www.fast77.com 1972 - 330 hp crate, 11" lift with 39x18 mickeys. 3/4 ton, cross steer, 4 wheel disc brakes 1996 Z71 w/ 35's

06-09-2006, 11:32 AM	#2
Burt4x4 Registered User Join Date: Feb 2000 Location: Modesto, CA Posts: 1,842	Re: Vacuum issues - help me gents Could be? What I would do is get a can of carb cleaner, fire up your rig and now spray the fluid around your booster, being careful and watch were you spray, when you hear your rpm go up you have found the vacume leak..depending on were it is will steer you to the fix Good Luck Burt __________________ 1972 K5 MPFI454/Sm465/Np205/D60/14FFd/Re-Centerd H1s w/Swamper Iroks

06-09-2006, 12:45 PM	#4
Jason915 Registered User Join Date: Jan 2005 Location: Colorado Springs Posts: 693	Re: Vacuum issues - help me gents I would isolate the problem by disconnecting the vacuum line to the booster and see if it goes away. Also a cheap vacuum gauge is very helpful. Good luck __________________ 1971 GMC K1500 SWB Fleetside, 4" skyjacker softride and, 14 Bolt FF, HD Dana 44 4.10's 1970 K5 TBI conversion lifted etc SOLD 1968 C20 camper truck SOLD “To ban guns because criminals use them is to tell the innocent and law-abiding that their rights and liberties depend not on their own conduct, but on the conduct of the guilty and the lawless.” Jeff Snyder

06-09-2006, 12:51 PM	#5
JMac11 Registered User Join Date: May 2005 Location: Tallahassee Fl Posts: 773	Re: Vacuum issues - help me gents Replaced all my vacuum lines and Booster, truck would not idle. Quit counting the turns of the idle screws at 6. Takes about 12 foot to replace all your under dash ones.

06-09-2006, 01:08 PM	#6
makovai Senior Member Join Date: Feb 2006 Location: oregon city Posts: 335	Re: Vacuum issues - help me gents funny thing is i have a vacuum gage. Put it in couple weeks ago in the blank spot next to the oil pressure gage. It really doesn't show that im low on vacuum, although my brakes have never work very well. I wrote a thread a while back about switching to a hydraboost. I bought one but never installed it. Maybe I've have a bad booster since i bought the rig. Beside...... brakes are overatted, all they do is slow you down. __________________ If it aint broke..............fix it till it is. www.fast77.com 1972 - 330 hp crate, 11" lift with 39x18 mickeys. 3/4 ton, cross steer, 4 wheel disc brakes 1996 Z71 w/ 35's

06-09-2006, 03:53 PM	#7
FRENCHBLUE72 PROJECT 7DEUCE Join Date: Dec 2002 Location: GRANTS PASS OR Posts: 21,591	Re: Vacuum issues - help me gents Sounds like now is a great time to swap to the hydro set-up.. __________________ GO BIG GREEN GO DUCKS MEMBER #6377 72 k-5 daily driver 6'' lift 35'' 350-350-205 slowly getting rust free. Project "7DEUCE" check out my build http://67-72chevytrucks.com/vboard/s...d.php?t=267665 Tim Powell..R.I.P EastSideLowlife..... R.I.P..

06-09-2006, 04:37 PM	#8
Burt4x4 Registered User Join Date: Feb 2000 Location: Modesto, CA Posts: 1,842	Re: Vacuum issues - help me gents What I did is upgrade my booster to 1ton. 1/2ton truck have a single diaphram booster were 1ton uses a double. WOW! I can actualyl lock up my 35" swampers now. HUGE improvement. Simply when to Autozone (they carry AC Delco) and ordered a Master/Booster set for a 1972 K30 1ton 4x4 p/u. My brake are better than ever! Burt __________________ 1972 K5 MPFI454/Sm465/Np205/D60/14FFd/Re-Centerd H1s w/Swamper Iroks

06-10-2006, 08:27 AM	#9
makovai Senior Member Join Date: Feb 2006 Location: oregon city Posts: 335	Re: Vacuum issues - help me gents damn...i got to this post after i bought a replacement booster. That was the problem. The brakes work a little better, but the biggest thing is the vacuum leak is gone. Now i kinda wish i would have bought a 1 ton booster. I cannot nor have i ever been able to lock my brakes up. __________________ If it aint broke..............fix it till it is. www.fast77.com 1972 - 330 hp crate, 11" lift with 39x18 mickeys. 3/4 ton, cross steer, 4 wheel disc brakes 1996 Z71 w/ 35's

06-10-2006, 11:26 AM	#10
DEFIANT NCC-74205 Registered User Join Date: Aug 2005 Location: POCONO MTS PA Posts: 64	Re: Vacuum issues - help me gents I put in a 1 ton too. Got it a while back in the yard. Works good. I've considered hydro-boost, but abandoned the idea. Just more hoses to leak and when your power steering pump takes a dump you loose your brakes. Another way to decrease brake effort is to get a master cylinder with a smaller bore. That's right a smaller bore increases brake pressure and reduces effort. Well at least you fixed your vacuum leak. Another good way to check for vacuum leaks is by squirting water. Works like a can of carb cleaner, but makes a nice slurping sound when you find the leak and it makes the engine rpm drop when sucked in. "If at first you don't succeed, keep on sucking 'till you do succeed" - Curly Howard __________________ To go with honor and courage, a far and wonderous distance Last edited by DEFIANT NCC-74205; 06-10-2006 at 11:27 AM.



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