Corvette Vacuum Reservoir Tank
Thread Starter
Safety Car
Joined: Sep 2013
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From: Draper Utah
Corvette Vacuum Reservoir Tank
Has anyone installed a 1980-82 coffee can vacuum reservoir tank in a chrome bumper Corvette? My car is a 1970 and I believe the reservoir thank might have a small leak as my vacuum system bleeds down after a couple of hours. Everything else in the vacuum system is new and been tested and I'm pretty sure the vacuum tank is the problem, but it's really hard to tell as the system bleeds down so slowly it takes forever to check. Every time I move the clamps blocking off certain sections I have to spend an hour to see if I've isolated the leak. Since the 80-82 tanks can be had for $50 I'd be way ahead to just buy one and test it as my time is worth a lot more than sitting and watching paint dry.... err... I mean air escape.
Honestly the losing vacuum pressure slowly doesn't really bother me. The part that bothers me is after about an hour the wiper door pops open as the vacuum escapes and the door goes back down about 15 minutes later. If anyone knew an easy way to stop that from happening I'd do it.
And if someone installed an 80-82 coffee can vacuum reservoir tank where did you put it and how did you mount it?
Honestly the losing vacuum pressure slowly doesn't really bother me. The part that bothers me is after about an hour the wiper door pops open as the vacuum escapes and the door goes back down about 15 minutes later. If anyone knew an easy way to stop that from happening I'd do it.
And if someone installed an 80-82 coffee can vacuum reservoir tank where did you put it and how did you mount it?
Team Owner
Joined: Sep 2006
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From: Westminster Maryland
Hi I,
From what you describe I really don't think the situation you're seeing is caused by the vacuum storage tank.
How have you been testing all the door and headlight components? Do you have a small pump like a mity-vac w/gauge and a trouble shooting guide?
It's sad to say but presently a new part is no guarantee of a properly functioning part.
Regards,
Alan
From what you describe I really don't think the situation you're seeing is caused by the vacuum storage tank.
How have you been testing all the door and headlight components? Do you have a small pump like a mity-vac w/gauge and a trouble shooting guide?
It's sad to say but presently a new part is no guarantee of a properly functioning part.
Regards,
Alan
Thread Starter
Safety Car
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From: Draper Utah
Thanks for the reply. I have a mity-vac and a troubleshooting guide. I have been testing the system by applying vacuum and blocking off/isolating different sections of the system. I have an excellent understanding of the vacuum system as I've now replaced every vacuum part and hose except the reservoir and I've been chasing this vacuum leak all summer. I also tested all the new parts before installing them. (For the record two vacuum relays and one headlight override switch were faulty when I received them). My biggest problem is it takes so long every time I run a different test as the system leaks down so slowly. My current though is to just install a new vacuum tank and see if it fixes the problem, the only downside is pulling the stock vacuum tank out would be a major undertaking.
I'm open to any suggestions on how to track/fix this issue.
I'm open to any suggestions on how to track/fix this issue.
Thread Starter
Safety Car
Joined: Sep 2013
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From: Draper Utah
Corvette Vacuum Reservoir Tank
That's exactly what I'm thinking, I would like to hear from someone that has done this and see where and how they mounted the tank. I'd also like to see how they plumbed the system. I'm willing to learn from others experience/mistakes.
Le Mans Master
Joined: Dec 2006
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Thanks for the reply. I have a mity-vac and a troubleshooting guide. I have been testing the system by applying vacuum and blocking off/isolating different sections of the system. I have an excellent understanding of the vacuum system as I've now replaced every vacuum part and hose except the reservoir and I've been chasing this vacuum leak all summer. I also tested all the new parts before installing them. (For the record two vacuum relays and one headlight override switch were faulty when I received them). My biggest problem is it takes so long every time I run a different test as the system leaks down so slowly. My current though is to just install a new vacuum tank and see if it fixes the problem, the only downside is pulling the stock vacuum tank out would be a major undertaking.
I'm open to any suggestions on how to track/fix this issue.
I'm open to any suggestions on how to track/fix this issue.
I would test the tank. Put some vacuum line and a bicycle pump with a needle valve, give it 5 lbs, and submerge it in water. You can solder a pin hole shut.
I went thru all this BS years ago, and need to check it all again. Half the repop parts were crap just like you found.
Thread Starter
Safety Car
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From: Draper Utah
Corvette Vacuum Reservoir Tank
I have four check valves from three different manufacturers sitting on my work bench, they all test good. Removing and repairing the stock vacuum tank is my first choice but its not a simple fix as I have headers, ps and power brakes so removing the stock tank is a major undertaking as all those must be removed along with the steering column (at least that's how I see it.
Drifting
Joined: Jul 2006
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From: Deplorableville Nebraska
How I test the storage tanks;
You have a '70 car, therefore you should have 3 ports coming off the storage tank. Simply connect any 2 ports together with surplus vacuum hose making sure that the connections are tight.
I use a 3 way connector to run a separate vacuum gauge inline with my vacuum pump. If I have access to a wall plug, I use an electric pump. It is actually a surplus medical aspirator, rated at less than 1 cfm. If not I have to hand pump quite a bit to get a vacuum reading. I simply pump to achieve a vacuum reading and then pinch off the line with vice grips after the 3 way and before the pump. You can now remove the pump and can observe the reading on the gauge over time.
You have a '70 car, therefore you should have 3 ports coming off the storage tank. Simply connect any 2 ports together with surplus vacuum hose making sure that the connections are tight.
I use a 3 way connector to run a separate vacuum gauge inline with my vacuum pump. If I have access to a wall plug, I use an electric pump. It is actually a surplus medical aspirator, rated at less than 1 cfm. If not I have to hand pump quite a bit to get a vacuum reading. I simply pump to achieve a vacuum reading and then pinch off the line with vice grips after the 3 way and before the pump. You can now remove the pump and can observe the reading on the gauge over time.
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Thread Starter
Safety Car
Joined: Sep 2013
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From: Draper Utah
Corvette Vacuum Reservoir Tank
That's basically what I did to test the tank and why I believe it is causing my issues.
I can't believe one super tiny leak can cause so many problems.
I can't believe one super tiny leak can cause so many problems.
Thread Starter
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From: Draper Utah
Corvette Vacuum Reservoir Tank
What happens if I just bypass the vacuum reservoir? I understand I'll lose the ability to operate the headlights with the engine off. But will everything function correctly? If a bypass helps me isolate the issue for certain it's simple to rig for testing.
Drifting
Joined: Jul 2006
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From: Deplorableville Nebraska
What happens if I just bypass the vacuum reservoir? I understand I'll lose the ability to operate the headlights with the engine off. But will everything function correctly? If a bypass helps me isolate the issue for certain it's simple to rig for testing.
Have you tested the vacuum valve on the headlight switch? And have you bypassed the hvac system port for your system test?
Thread Starter
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From: Draper Utah
Corvette Vacuum Reservoir Tank
Yes to both questions. At the moment the HVAC system is bypassed for testing. Testing and replacing the headlight switch along with its hoses was last weekends project. The small hose side of my system appears to be holding vacuum.
Team Owner
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From: Southbound
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Melting Slicks
Joined: Apr 2009
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From: Great Plains Iowa
In the 27 years I have been working on these C3's I have found its almost always a leaking relay valve spool because the relay valves made now days are pretty crappy. I have had limited success lubing the spools with an ordinary air motor oil so you could try that. For those early C3's that have the wiper doors the wiper park valve is very often the cause of a vacuum loss.
Thread Starter
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From: Draper Utah
Corvette Vacuum Reservoir Tank
I will recheck my relay valves (for at least the fifth time) as two of the five relay valves I just purchased have failed within a week. The wiper park valve is NOT the issue as it was replaced last week with one made in the USA and the wiper system is currently isolated from the system. I'll worry about integrating the wiper system after I get the headlight vacuum leak fixed. This would be much easier to track if the leak was not so small/slow.
Melting Slicks
Joined: Apr 2009
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From: Great Plains Iowa
I will recheck my relay valves (for at least the fifth time) as two of the five relay valves I just purchased have failed within a week. The wiper park valve is NOT the issue as it was replaced last week with one made in the USA and the wiper system is currently isolated from the system. I'll worry about integrating the wiper system after I get the headlight vacuum leak fixed. This would be much easier to track if the leak was not so small/slow.
During the last couple of weeks my wiper door has been opening and closing every time I start it so I also have a vacuum leak. These Chinese-made relay valves just don't last very long as you have discovered. It gets tiresome, huh?
Melting Slicks
Joined: May 2015
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From: Cape Girardeau Missouri
Have you considered putting the vacuum tank under a few psi of positive pressure and checking for a leak with a liquid leak detector (like used for natural gas) that gives a strong visible indication of even the tiniest leak? Even if you have some small leaks around the connections it won't affect your search in the tank body.
Team Owner
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From: Crossville TN
You know that sealing up a leak in the reservoir tank means putting a simple patch on the OUTSIDE. Just get some clay or putty and move it from place to place on that tank while doing a 'leak-down' test with vacuum gauge installed. When the vacuum gauge stabilizes, you've found the leak.
P.S. That tank is fairly large. When you first put a vacuum on it, you will get some variation in the vacuum readings untill the volume stabilizes (usually less than 10 seconds). After that, the readings should be fairly stable, unless it has a leak. Oh, don't forget that the hoses, pump, and/or gauge you are using for your testing can have leaks, too!!
P.S. That tank is fairly large. When you first put a vacuum on it, you will get some variation in the vacuum readings untill the volume stabilizes (usually less than 10 seconds). After that, the readings should be fairly stable, unless it has a leak. Oh, don't forget that the hoses, pump, and/or gauge you are using for your testing can have leaks, too!!
Team Owner
Joined: Jul 1999
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From: Orange Park Florida
My '72 had a tank that looked like a mini gas tank, like maybe for a lawn mower, and 3 nipples on it, for the larger vac hoses......trouble with it was that all the flexing in it's life, it was in '95 the thing proved to have so many stress cracks in it, not even bother to try fixing, I just ran without it.....in '98 down here in Florida, I hit a damn deer at night...wiped out both operating headlights, hell with it, never liked them anyway.....went sugar scoop Ecklers, since modified for modern lo profile bulbs.....and huge holes reduced to 1/2 size/fore-aft....
wiper door eventually electrified .....
vacuum sux......
wiper door eventually electrified .....
vacuum sux......
Team Owner
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From: Crossville TN
"...vacuum sux..."
Well, yes. That's the point. Vacuum is a 'differential pressure' (from atmospheric} that can be used to do work; and it's a FREE waste-product of IC engine operation. Why not use it?
P.S. And, if you get your ring finger caught in a vacuum hose, the ring won't glow red and melt your finger off.
Well, yes. That's the point. Vacuum is a 'differential pressure' (from atmospheric} that can be used to do work; and it's a FREE waste-product of IC engine operation. Why not use it?
P.S. And, if you get your ring finger caught in a vacuum hose, the ring won't glow red and melt your finger off.