1972 LT1 Vacuum
Thread Starter
Burning Brakes
Joined: Sep 2010
Posts: 799
Likes: 26
From: Lexington Park Maryland
1972 LT1 Vacuum
After reading TONS of post on Vacuum system for the headlights and wipers, I discovered in my car someone had bypass the "boxy" looking vacumm canister mounted under the driver side fender above the fuel vapor canister and capped of a vacuum line coming out from the firewall on the passenger side hood latch. I'll photos and post later.
so, what's the benefits for bypassing the vacuum canister and capping off vacuum lines. The heahlight use to pop out according tot he previous owner, now they don't do anything but come on.
so, what's the benefits for bypassing the vacuum canister and capping off vacuum lines. The heahlight use to pop out according tot he previous owner, now they don't do anything but come on.
Former Vendor
Joined: Aug 2006
Posts: 76,656
Likes: 1,851
From: Jeffersonville Indiana 812-288-7103
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15
The vacuum reservoir may have a crack in it and be leaking.... that would be the only reason I would know of for someone to bypass it. They do crack around where the nipples are for the hoses and sometimes these cracks are very hard to detect.
Thread Starter
Burning Brakes
Joined: Sep 2010
Posts: 799
Likes: 26
From: Lexington Park Maryland
Can I plugged two of three port and use a vacumm pump to test it. can it be replaced if it is bad? by the way the Vacuum diagram I found useful was the one you posted in one of the post you answered. thank you for that. I planned on taking several photos of other vacuum issues I think might contribute to my problem, two were under the center cousel that control the vent inside the car. I'll them when I have the pictures.
Last edited by newbie2vette; Nov 15, 2010 at 02:14 PM.
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,116
From: Crossville TN
Yes. You can test the integrity of the vacuum reservoir as you suggest. If it leaks, you can search around the tank to see if you can locate the point of leakage (use clay or play-doh to slap onto it to act as a temporary seal; keep moving it until you locate the problem area(s). And, since it is a vacuum tank, you merely need to put a smear of JB Weld epoxy (I like the stick type that you knead into a putty best) over the leak path [after you clean it good with solvents, of course] and it should seal just fine. No need to remove the tank, unless you can't locate the leaks.
Thread Starter
Burning Brakes
Joined: Sep 2010
Posts: 799
Likes: 26
From: Lexington Park Maryland
Yes. You can test the integrity of the vacuum reservoir as you suggest. If it leaks, you can search around the tank to see if you can locate the point of leakage (use clay or play-doh to slap onto it to act as a temporary seal; keep moving it until you locate the problem area(s). And, since it is a vacuum tank, you merely need to put a smear of JB Weld epoxy (I like the stick type that you knead into a putty best) over the leak path [after you clean it good with solvents, of course] and it should seal just fine. No need to remove the tank, unless you can't locate the leaks.
Team Owner
Joined: Sep 2006
Posts: 31,229
Likes: 4,321
From: Westminster Maryland
Hi n2v,
72 LT-!, NICE!!!
I'll alert you to how involved getting the vacuum tank out of the car can be, if it comes to that.
Even with the vapor canister removed you can't drop the tank straight down. On non p/b cars, if the master cylinder is unbolted from the firewall and pushed toward the engine, the tank can be extracted. Removing from a p/b brake car is even trickier because of the booster.
Good Luck working on your headlights and wipers, they can be a real challenge.
Regards,
Alan
72 LT-!, NICE!!!
I'll alert you to how involved getting the vacuum tank out of the car can be, if it comes to that.
Even with the vapor canister removed you can't drop the tank straight down. On non p/b cars, if the master cylinder is unbolted from the firewall and pushed toward the engine, the tank can be extracted. Removing from a p/b brake car is even trickier because of the booster.
Good Luck working on your headlights and wipers, they can be a real challenge.
Regards,
Alan
Thread Starter
Burning Brakes
Joined: Sep 2010
Posts: 799
Likes: 26
From: Lexington Park Maryland
As I am looking around the site I am discovering more and more parts that could play into this. I think I found these by mistakte, wiper over-ride switch and vacuum over-ride switch. they are located under the steering wheel. Can someone give me a functionality description of these parts. what do they you? when are they used? what position should they be during normal condition?
Race Director
Joined: May 2006
Posts: 16,528
Likes: 53
From: Dayton, Ohio
This should help. Click on supporting documentation.
http://willcoxcorvette.com/repairand...lp.php?hID=218
http://willcoxcorvette.com/instructi...ted_080509.pdf
http://willcoxcorvette.com/repairand...lp.php?hID=218
http://willcoxcorvette.com/instructi...ted_080509.pdf
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Team Owner
Joined: Sep 2006
Posts: 31,229
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From: Westminster Maryland
Hi n2v,
There's lots of info available as Roger indicated.
I'd suggest you buy a Headlight/Wiper trouble shooting guide from Dr. Rebuild, and a vacuum pump with a gauge, like a Mity-Vac.
These 2 things will allow you to understand and test the function of the MANY parts to the 2 systems.
Regards,
Alan
There's lots of info available as Roger indicated.
I'd suggest you buy a Headlight/Wiper trouble shooting guide from Dr. Rebuild, and a vacuum pump with a gauge, like a Mity-Vac.
These 2 things will allow you to understand and test the function of the MANY parts to the 2 systems.
Regards,
Alan
Thread Starter
Burning Brakes
Joined: Sep 2010
Posts: 799
Likes: 26
From: Lexington Park Maryland
This should help. Click on supporting documentation.
http://willcoxcorvette.com/repairand...lp.php?hID=218
http://willcoxcorvette.com/instructi...ted_080509.pdf
http://willcoxcorvette.com/repairand...lp.php?hID=218
http://willcoxcorvette.com/instructi...ted_080509.pdf
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,116
From: Crossville TN
You must check out the tank and get it sealed first. Then you can move on to other sections of the vacuum system to test for leaks. Probably 50% of all vacuum systems can be fixed with minor corrections. Your best strategy is to test one section of the system at a time by blocking off the others (pulling and plugging a hose), then testing components in that line for proper function..individually..until you locate any defective components. Don't just throw money at it until you 'get lucky' and happen to change the one that is giving you the problem. Spend a few bucks for a vacuum gage and a vacuum system diagnostic paper (around $10 from some of the Corvette parts vendors). Read it over and follow directions. Once you know how the system works and what the hose routing is supposed to look like, you can work on yours very easily.
Team Owner
Joined: Jun 2000
Posts: 38,923
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From: Southbound
Cruise-In II Veteran
Newbie2...order an owner's manual for your 72. Lots of useful information in the owner's manual, including the overrides under the dash.
FWIW: if your vacuum reserve can is leaking, the overrides probably will not work with the engine off.
FWIW: if your vacuum reserve can is leaking, the overrides probably will not work with the engine off.
Former Vendor
Joined: Aug 2006
Posts: 76,656
Likes: 1,851
From: Jeffersonville Indiana 812-288-7103
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15
when you get to the page links on the site Roger posted, just click on supporting documentation. You'll need to have Adobe Reader to view the files but that is free from Adobe.com.
Willcox
Willcox
Thread Starter
Burning Brakes
Joined: Sep 2010
Posts: 799
Likes: 26
From: Lexington Park Maryland
A maintenance manual came with the car, but it's one of those you can get from your local parts store, not informative at all. Just your basic stuff is addressed. I for one is use to a detail manual. Where can I find a manual that specially address these model or several year span? I found additional vacuum hose not connected in the car. I definitely have some work on this vacuum system.
Race Director
Joined: May 2006
Posts: 16,528
Likes: 53
From: Dayton, Ohio
A maintenance manual came with the car, but it's one of those you can get from your local parts store, not informative at all. Just your basic stuff is addressed. I for one is use to a detail manual. Where can I find a manual that specially address these model or several year span? I found additional vacuum hose not connected in the car. I definitely have some work on this vacuum system.
Former Vendor
Joined: Aug 2006
Posts: 76,656
Likes: 1,851
From: Jeffersonville Indiana 812-288-7103
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15
Thread Starter
Burning Brakes
Joined: Sep 2010
Posts: 799
Likes: 26
From: Lexington Park Maryland
An update on my vacuum issue. Since I was re-doing the entire breake system which means taking the MC out I thought I would take the vacuum canister out while there is room. Applied 12 lbs. of vacuum let it stand over night no issue, the vacuum did not leaked out.
So, I am back to wondering why it was bypassed. As I mentioned I did find several "T" fitting with vacuum hose attached on two ends but the third does not have anything attached to it and found some vacuum hose inside the cockpit under the center counsel eaten by a mice. but there is third outlet that does not have anything attached to it.
I got involved with the taking the calipers and the rotors so I did not get the chance to take photos, which I will tomorrow. I sure would like to know what goes on this fittings.
So, I am back to wondering why it was bypassed. As I mentioned I did find several "T" fitting with vacuum hose attached on two ends but the third does not have anything attached to it and found some vacuum hose inside the cockpit under the center counsel eaten by a mice. but there is third outlet that does not have anything attached to it.
I got involved with the taking the calipers and the rotors so I did not get the chance to take photos, which I will tomorrow. I sure would like to know what goes on this fittings.
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,116
From: Crossville TN
I would guess that the previous owner had 'leakage' problems and assumed that the tank was at fault. I suspect that the check valve may have been defective, instead...but it could be other components or a loose hose connection, as well. Glad the tank is good. Good luck with your check out and repairs.
