Vacuum canister question.
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Junior User
Joined: Jul 2012
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From: Athens, GA...it rocks.
Vacuum canister question.
When I bought my 73 F100 with a 390, the vacuum canister was disconnected and bypassed with a "T" fitting (the third line was plugged on the T). I have since reconnected the vacuum canister. Since doing so, I've fixed quite a few problems, but I think I'm having some of my rough idle issues due to a vacuum leak. All open connections have been plugged, so my question is as follows: Can I bypass the vacuum canister and have no problems? All of the emissions junk is disconnected, and it has factory air. The A/C would actually blow through the panel and floor vents before reconnecting the can o beanz, but now it only blows through the top vents on the dash, no matter what the settings are...of course, it's not blowing cold air, but it's at least moving some air when normal.
Just wanted to know if bypassing the canister would have any negative effects?
NG
Just wanted to know if bypassing the canister would have any negative effects?
NG
FTE Chapter Leader
Joined: Aug 2011
Posts: 4,321
Likes: 13
From: Cave Spring Georgia
Nick,
Usually the can is what helps the A/C move the vent openings, sounds to me like you may have the can connected wrong.
Please feel free to join us on the Georgia Forum !!!!!
Georgia Chapter - Ford Truck Enthusiasts Forums
Usually the can is what helps the A/C move the vent openings, sounds to me like you may have the can connected wrong.
Please feel free to join us on the Georgia Forum !!!!!
Georgia Chapter - Ford Truck Enthusiasts Forums
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Junior User
Joined: Jul 2012
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From: Athens, GA...it rocks.
Okay...before, when it was bypassed, the AC would blow in the proper location (vent, panel, floor). When it's reconnected--no dice. Is the canister a one-way canister? If so, I'll try swapping the lines. It's rather loose, kinda rattles around a bit, and I wonder if it might not have a crack in the canister or a hole, leading to a vacuum leak.
Will bypassing the canister have any adverse effects?
NG
Will bypassing the canister have any adverse effects?
NG
MSEE
Joined: Apr 2004
Posts: 10,386
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From: Austin, TX
If you get rid of the canister, all your heater/AC controls will let go at wide open throttle when vacuum is low. It's supposed to be connected to the system through a 2-to-1 check valve along the firewall.
If your heater is effectively stuck on defrost, then that means you're not getting any vacuum out of the selector switch. This is caused by vacuum not being hooked up, or a bad switch. Reconnecting the canister is not going to fix the issue you're having because vacuum is high enough at idle anyway and the canister is effectively transparent because of the check valve in that instance.
If your heater is effectively stuck on defrost, then that means you're not getting any vacuum out of the selector switch. This is caused by vacuum not being hooked up, or a bad switch. Reconnecting the canister is not going to fix the issue you're having because vacuum is high enough at idle anyway and the canister is effectively transparent because of the check valve in that instance.
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Junior User
Joined: Jul 2012
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From: Athens, GA...it rocks.
Cool. Where is the vacuum check valve usually located? The PO disconnected a ton of vacuum lines and bypassed most everything. A lot of vacuum fittings weren't even capped off, been capping them, took the canister bypass out, and now it's stuck in defrost.
Hotshot
Joined: Apr 2009
Posts: 14,333
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From: Stanley, VA
Here are a few illustrations from the Ford parts catalog, maybe they'll help you some with the A/C.
Click on the .pdf links to view.
Click on the .pdf links to view.
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Junior User
Joined: Jul 2012
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From: Athens, GA...it rocks.
Found the vacuum leak...
So I found the vacuum leak...turns out it is my soup can/can o' beans vacuum reservoir. I'm gonna be replacing it soon, until then, I'm probably gonna bypass it. Thanks to everyone for your help. It's amazing how smooth the engine idles when the vacuum reservoir is out of the loop and bypassed--that vacuum leak reallllly messes things up on the idling side of things.
NG
NG
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On my 90, my coffee can looking vacuum canister helps run the heat and AC. I bypassed it at the fitting when it got a rust hole. No noticeable performance difference but the climate controls were weak. But that was in the fall when I use neither the heat or AC anyway. I replaced it with a new used one and my system has plenty of vacuum
Freshman User
Joined: Jun 2011
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From: Houston
I don't want to beat a dead horse and not sure if I should start a new thread but...after reading this thread I don't have a canister on the right side of the engine as shown in the parts breakdown but I did have one on the left which was long since removed. My A/C sounds like some of the vents are closed. Full fan with nothing coming from the vents. I'm trying to fix without taking the cab unit apart. I have a '77 F150 Ranger with a 400. Any photos out there with factory AC? I know I'm missing some parts.
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