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1/4/17 10:22am - Original Message: 'crushed vacuum can'
sPearson66/81
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deforest, WI - USA

Vette(s):
1981 work in progress

Joined: 12/14/2016
Posts: 13
what controls how much vacuum goes to the headlight vacuum tank mine was leaking so I fix it and after a quick trip to the store and back the can that once look like a coffee can now looks like a soup can     
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1/4/17 10:49pm - Reply: 'Re: crushed vacuum can'
73shark
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Overland Park, KS - USA

Vette(s):
1973 Orange Metallic Coupe (orig owner), L82, 4 spd (WR), PS, (A/C & PW (I installed from wrecked 73)), leather, AM/FM Stereo, ran with '65 FI unit earlier & will again some day.

Joined: 7/9/2003
Posts: 394
Have you check the integrity of the can?  I suspect that the can is deteriorated and can no longer sustain the 18 to 20 inches manifold vacuum. There is no vacuum reducer in the line.

____________________________________

1973 L-82 4 spd

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1/5/17 9:22am - Reply: 'Re: crushed vacuum can'
sPearson66/81
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deforest, WI - USA

Vette(s):
1981 work in progress

Joined: 12/14/2016
Posts: 13
yes I found a leak on top of the can fixed it with jb weld let it set up overnight and applied vacuum overnight and it held around 25 and after I reinstalled is when it self destructed prior to this the system was working okay the driver side would pop right up and the passenger side had a mind of its own so I check the tank first and would not hold any vacuum so I have ordered a new tank  and have replaced hoses and the filter, check valve, and override switch but looking on how the system is designed I'm just confused on what regulates the vacuum it pretty much runs from the manifold to the tank knowing the system has been is service for over 30 yrs I was just wondering and didn't want to sacrifice a new 45 dollar coffee can    
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1/5/17 8:24pm - Reply: 'Re: crushed vacuum can'
73shark
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Overland Park, KS - USA

Vette(s):
1973 Orange Metallic Coupe (orig owner), L82, 4 spd (WR), PS, (A/C & PW (I installed from wrecked 73)), leather, AM/FM Stereo, ran with '65 FI unit earlier & will again some day.

Joined: 7/9/2003
Posts: 394
There isn't any vacuum regulator.  Was the can deteriorated?  I assume the leak you repaired was caused by rust.

I just can't see how 25 inches of vacuum could crush the can if it was at full strength.


____________________________________

1973 L-82 4 spd

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1/6/17 1:06pm - Reply: 'Re: crushed vacuum can'
Adams' Apple Lifetime Member
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Duncanville, TX - USA

Vette(s):
#1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/ Am-Fm/map light National/Regional/Chapter NCRS "Top Flight" #2-1985 Bright Red/Carmine Cp.L-98/auto Member: NCRS, NCRS Texas, Corvette Legends of Texas

Joined: 11/8/2003
Posts: 19454
Tanks are really thin to begin with...not nearly as tough as a real coffee can. It is rusted out on the inside. Holding vacuum overnight is not the same as the vacuum that is applied while driving....especially when decelerating.
Cut that turd open, and you'll see why it failed...there's just not much metal in there originally, and a it don't take much rust to do them in. Ouch

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Joel Adams
C3VR Lifetime Member #56    
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1/10/17 5:03pm - Reply: 'Re: crushed vacuum can/ HELP'
sPearson66/81
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deforest, WI - USA

Vette(s):
1981 work in progress

Joined: 12/14/2016
Posts: 13
okay I got a brand new res tank and within  5 minutes warm up and reeving up and down the tank was crushed just like the repaired one the lights pop right up and down with the can intact and crushed so I put my vac tester on the hose coming out of the manifold to the filter to large port on the check valve and got a steady 15 hg at idle and 17 to 22 when reeved up and down.
from the way I see it from vette101 troubleshooting guide that tank is there to supply vacuum to the lights after the motor is shut down until I figure out what is the cause of my can crushing cant I pull a bubba and put a T where the 3 hose connect at the tank with out doing any damage to the relays and actuator's and making things worse. I just don't know ????   
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1/11/17 8:37am - Reply: 'Re: crushed vacuum can'
cinor Lifetime Member
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, - Canada

Vette(s):
1975 L48 Stingray 1992 LT1

Joined: 12/24/2013
Posts: 284
while we are on the topic of cans, I would like to stick my nose in with a question. Is there any reason to replace the can, it looks fine  could use a new filter. 

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1/11/17 2:53pm - Reply: 'Re: crushed vacuum can'
Adams' Apple Lifetime Member
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Duncanville, TX - USA

Vette(s):
#1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/ Am-Fm/map light National/Regional/Chapter NCRS "Top Flight" #2-1985 Bright Red/Carmine Cp.L-98/auto Member: NCRS, NCRS Texas, Corvette Legends of Texas

Joined: 11/8/2003
Posts: 19454
 The reservoir holds reserve vac to operate the headlights AND the HVAC components when you get heavy on the throttle. Without the reserve tank, the vac operated components would return to their "rest" positions every time you mashed the go pedal very hard. If you've ever driven an older(and some newer) Ford with A/C you know what I mean....you get on the throttle a little, and the A/C starts blowin out the defrost vent....aggravating as heck.  Censored

There's no real reason for the can to deform like that with "normal" vacuum unless the can is bad in some way. Perhaps it was just too thin....just because it's new don't mean it's good. A gas engine will only produce so much vacuum...23-23 inches on decell would be considered normal for a good running engine with no leaks.....not enough to suck the reservoir inside out like that.
You can certainly connect the relays to straight vacuum without the reservoir with no ill effects other than the previously mentioned issues with stuff moving during heavy throttle....headlights have been known to flop open/shut while driving. I'd sure be suspicious of a new reservoir that failed that quickly.......

____________________________________
Joel Adams
C3VR Lifetime Member #56    
My Link


(click for Texas-sized view!)
             NCRS

"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"
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1/11/17 8:36pm - Reply: 'Re: crushed vacuum can'
sPearson66/81
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deforest, WI - USA

Vette(s):
1981 work in progress

Joined: 12/14/2016
Posts: 13
I'll send it back and get a replacement and see what happens in the mean time ill do some poking around with vac tester to see if I get some off the charts reading all I can say about her health is I know she is running extremely RICH which I'm still not sure witch avenue I'm going to take to correct it for all the money I've thrown at the q-jet it should be gold plated  just hoping the two problems aren't related or are they idk ????????????????
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1/11/17 9:41pm - Reply: 'Re: crushed vacuum can'
73shark
Standard Member
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Overland Park, KS - USA

Vette(s):
1973 Orange Metallic Coupe (orig owner), L82, 4 spd (WR), PS, (A/C & PW (I installed from wrecked 73)), leather, AM/FM Stereo, ran with '65 FI unit earlier & will again some day.

Joined: 7/9/2003
Posts: 394
cinor said: while we are on the topic of cans, I would like to stick my nose in with a question. Is there any reason to replace the can, it looks fine  could use a new filter. 


If your can that requires a filter is located behind the driver side front wheel, then that's the charcoal canister that captures gas vapors when the engine is off. Your vacuum reservoir is that big, horizontal pipe behind the bumper that started in '73.

If headlites flop under heavy acceleration, the problem is not the vacuum reservoir since it only requires vacuum to change positions, not hold them in the open or closed position.


____________________________________

1973 L-82 4 spd

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1/11/17 10:36pm - Reply: 'Re: crushed vacuum can'
73shark
Standard Member
- Send Private Message


Overland Park, KS - USA

Vette(s):
1973 Orange Metallic Coupe (orig owner), L82, 4 spd (WR), PS, (A/C & PW (I installed from wrecked 73)), leather, AM/FM Stereo, ran with '65 FI unit earlier & will again some day.

Joined: 7/9/2003
Posts: 394
sPearson66/81 said: I'll send it back and get a replacement and see what happens in the mean time ill do some poking around with vac tester to see if I get some off the charts reading all I can say about her health is I know she is running extremely RICH which I'm still not sure witch avenue I'm going to take to correct it for all the money I've thrown at the q-jet it should be gold plated  just hoping the two problems aren't related or are they idk ????????????????


The two most common reasons for a Q-jet to run rich are leaking plugs under the secondary wells or a float that has become saturated and no longer floats.


____________________________________

1973 L-82 4 spd

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1/12/17 7:46am - Reply: 'Re: crushed vacuum can'
cinor Lifetime Member
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, - Canada

Vette(s):
1975 L48 Stingray 1992 LT1

Joined: 12/24/2013
Posts: 284
73shark said:
cinor said: while we are on the topic of cans, I would like to stick my nose in with a question. Is there any reason to replace the can, it looks fine  could use a new filter. 


If your can that requires a filter is located behind the driver side front wheel, then that's the charcoal canister that captures gas vapors when the engine is off. Your vacuum reservoir is that big, horizontal pipe behind the bumper that started in '73.

If headlites flop under heavy acceleration, the problem is not the vacuum reservoir since it only requires vacuum to change positions, not hold them in the open or closed position.
yep never even thought, I just seen can and thought oh hey I wonder.




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