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Topic: Vacuum leak

in Forum: C3 Cooling and Heating Systems


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Vacuum leak (1/8)
 11/13/11 10:06am
Shawnee2
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Cherryville, NC - USA

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82 Collector


Joined: 1/10/2011
Posts: 84

I have fixed all the vacuum leaks I can find on the HVAC system and replaced the selector valve.  I still seem to have a vacuum leak once everything is connected.  I have seperated the headlight system off the HVAC so I can only deal with it at this time.  I have individually checked all the lines coming off the back of the selector which all hold vacuum.  As soon as I connect the selector switch back up (new switch, old switch fell apart) I can not hold any vacuum out in the engine bay at the connector that T's off to the healight system.  If I pull the connector off at the selector switch and plug the black hose I have vacuum.  Is my new selector switch bad? 

I do not understand the chart in the SM when it refers to seal/vac/vent.  Is there a vent for the vacuum (on the water switch?) that could be venting my system all the time?
 
 
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Re: Vacuum leak (2/8)
 11/13/11 12:00pm
rraider1
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Woodland, WA - USA

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Re: Vacuum leak (3/8)
 11/13/11 12:41pm
Shawnee2
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Cherryville, NC - USA

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Bob, thanks for the information.  I have used these two charts to diagnose my issues and found my leaks.  What is do not understand is the chart on the left side of the first link.  I am assuming that when selector switch is in the off  or heat position the black line is sealed off and I should have hold vacuum in the engine bay port.  If I move the selector switch to DEF, I should have vacuum on the blue line only.  My issue seems to be that the black line is not sealing at the selector switch.
 
Am I understanding this correctly?  
Re: Vacuum leak (4/8)
 11/13/11 1:29pm
anips
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sonoma, CA - USA

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the leak may be in the source line, maybe a leak at the eng. vac. ck. valve, the vac. filter, or the tank.

|UPDATED|11/13/2011 10:29:41 AM (AZT)|/UPDATED|
Re: Vacuum leak (5/8)
 11/13/11 3:46pm
Shawnee2
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Cherryville, NC - USA

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82 Collector


Joined: 1/10/2011
Posts: 84

I have everything disconnected except the HVAC system.  I am using a vacuum pump on the small line going to the HVAC system so nothing else should be a factor.  I have checked all the individual lines (black, green, tan, etc) at the selector switch connector and each holds vacuum to the appropriate part of the system.  My issue arises when I connect the five hose connector to the selector valve and check the vacuum on the small black hose in the engine bay that feeds the complete system.  I am leaning towards a bad selector valve switch but this is new so I would not think it is bad.  I do not hear any air leaks at the connector when I apply vacuum.
Re: Vacuum leak (6/8)
 11/13/11 4:08pm
rraider1
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Woodland, WA - USA

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I think your question is a good one should the control hold vacum in the off position, I hope someone knows for sure. But I believe that if it switches vacum to the correct spots and shuts it off to spots that are off its ok I dont think it will stay air tight. it will bleed off after time buty not sure
Re: Vacuum leak (7/8)
 11/30/11 7:58pm
Shawnee2
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Cherryville, NC - USA

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OK, figured out the problem.  As I thought, the control valve in the off position should seal the main input line off and seal the system back to the check valve at the manifold.  The recently purchased aftermarket valve would not seal unless I clamped it together harder.  I used parts off the new valve to fix the OEM valve and the system sealed with not leaks.  As soon as you move the control valve to another location, you can pull a vacuum on the sytem from that point.
 
Off to the next project...
Re: Vacuum leak (8/8)
 11/30/11 8:42pm
corvette440hpLifetime Member
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Jeff, isn't getting it fixed feel good? Next project for C3's is a never ending battle, but hey it's worth it. Oh yeah, it keeps you out of the bars, and from chasing women.Wink  

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corvette440hp
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