Vac lines, Do i need both?
Vac lines, Do i need both?
okay, so i've done an A/C Delete on my car and i also removed the Heater Control Vacuum Tank,
Now, Since i removed that tank, ( not using cruise ), Should i keep these 2 vac lines and hook them up, or can i remove them?


let me know, Thanks!
Now, Since i removed that tank, ( not using cruise ), Should i keep these 2 vac lines and hook them up, or can i remove them?


let me know, Thanks!
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Joined: Nov 2007
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From: windsor, ontario
Car: 87 mustang gt 89 camaro
Engine: 302 355 tpi
Transmission: manual
Axle/Gears: 3.55 and 3.42 posi
Re: Vac lines, Do i need both?
no u will not nees to connect those lines just plug off the ports from the intake
Re: Vac lines, Do i need both?
Im aware, but you just replied i dont need them and cap them off, my question is, do i need both of them, and if i hook both of them up, even thought i dont have my Vacuum tank on my car, will my heat still work fine.
Supreme Member
Joined: Sep 2002
Posts: 9,192
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From: Cary, North Carolina
Car: 1992 RS
Engine: Carbed 350
Transmission: 700R4
Axle/Gears: 3.42 posi
Re: Vac lines, Do i need both?
You will not be able to direct whether the heat runs to the defrost vents, the dash vents, or the floor vents without that vacuum line (the shorter one). Heat will work, but will ONLY come out the defrost vents. If you want to control where the heater blows out, you'll need to keep that line.
And then I'm not sure how well it will work without the vacuum tank that you say you took out. I'm assuming you mean the round ball under the headlight. Since it's really not seen and not in the way of anything, can I ask why you removed the vacuum tank? It holds vacuum for those heater controls to work, as well as holding vacuum for the cruise control (which you aren't using) - there are times when there's not enough vacuum available to maintain the heater control in the position you choose, and to keep the air from always switching between the defroster vents (the default setting) and the other vents, that vacuum tank was used by factory.
The longer vacuum line looks like the one that originally runs to the MAP sensor which was mounted on the firewall lip just under the hood and just above the heater box.
And then I'm not sure how well it will work without the vacuum tank that you say you took out. I'm assuming you mean the round ball under the headlight. Since it's really not seen and not in the way of anything, can I ask why you removed the vacuum tank? It holds vacuum for those heater controls to work, as well as holding vacuum for the cruise control (which you aren't using) - there are times when there's not enough vacuum available to maintain the heater control in the position you choose, and to keep the air from always switching between the defroster vents (the default setting) and the other vents, that vacuum tank was used by factory.
The longer vacuum line looks like the one that originally runs to the MAP sensor which was mounted on the firewall lip just under the hood and just above the heater box.
Joined: Apr 2005
Posts: 7,736
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From: Not in Kansas anymore
Car: 82 Z28
Engine: 383 SP EFI/ 4150 TB
Transmission: T400
Axle/Gears: QP 9" 3.73
Re: Vac lines, Do i need both?

Every time you accelerate your vent position will change without the ball connected.
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Last edited by vetteoz; Oct 9, 2009 at 08:35 AM.
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Re: Vac lines, Do i need both?
You will not be able to direct whether the heat runs to the defrost vents, the dash vents, or the floor vents without that vacuum line (the shorter one). Heat will work, but will ONLY come out the defrost vents. If you want to control where the heater blows out, you'll need to keep that line.
And then I'm not sure how well it will work without the vacuum tank that you say you took out. I'm assuming you mean the round ball under the headlight. Since it's really not seen and not in the way of anything, can I ask why you removed the vacuum tank? It holds vacuum for those heater controls to work, as well as holding vacuum for the cruise control (which you aren't using) - there are times when there's not enough vacuum available to maintain the heater control in the position you choose, and to keep the air from always switching between the defroster vents (the default setting) and the other vents, that vacuum tank was used by factory.
The longer vacuum line looks like the one that originally runs to the MAP sensor which was mounted on the firewall lip just under the hood and just above the heater box.
And then I'm not sure how well it will work without the vacuum tank that you say you took out. I'm assuming you mean the round ball under the headlight. Since it's really not seen and not in the way of anything, can I ask why you removed the vacuum tank? It holds vacuum for those heater controls to work, as well as holding vacuum for the cruise control (which you aren't using) - there are times when there's not enough vacuum available to maintain the heater control in the position you choose, and to keep the air from always switching between the defroster vents (the default setting) and the other vents, that vacuum tank was used by factory.
The longer vacuum line looks like the one that originally runs to the MAP sensor which was mounted on the firewall lip just under the hood and just above the heater box.
Joined: Apr 2005
Posts: 7,736
Likes: 14
From: Not in Kansas anymore
Car: 82 Z28
Engine: 383 SP EFI/ 4150 TB
Transmission: T400
Axle/Gears: QP 9" 3.73
Re: Vac lines, Do i need both?
The round thing with the T is the check valve that keeps vac in your ball IF you have it fitted.
Line through firewall goes to heater , short rubber line off check valve goes to intake .The side port is what is connected to the ball. If not running the ball remove the check valve and run line direct to intake.
Line through firewall goes to heater , short rubber line off check valve goes to intake .The side port is what is connected to the ball. If not running the ball remove the check valve and run line direct to intake.
Supreme Member
Joined: Sep 2002
Posts: 9,192
Likes: 19
From: Cary, North Carolina
Car: 1992 RS
Engine: Carbed 350
Transmission: 700R4
Axle/Gears: 3.42 posi
Re: Vac lines, Do i need both?
The long one runs to the Heater Diverter Valve! This is a round valve, looks like a UFO on the top, and has coolant lines running to/from it. This vacuum line is given vacuum from the heater control valve when the settings are set to warm air, which activates the heater diverter valve, opening it to allow the warm coolant to circulate through the heater core. When the controls are set to cool air, the vacuum is switched off to the heater diverter valve closing off the warm coolant flow to the heater core to keep the cabin cool so that hot coolant isn't constantly circulating through the heater core in the cabin.
The short one runs to the heater controls. The little check valve keeps vacuum from escaping backwards when there's low vacuum, so that the vents don't change constantly while driving (this also assumes the vacuum ball is connected).
So - vacuum goes IN to the heater controls via the short line, and the controls sends vacuum OUT to the heater diverter valve when the air is set to warm to open the valve and let hot coolant circulate through the heater core in the cabin.
I'm thinking that you've removed the heater diverter valve, as this thing is ugly and most folks delete it out of the system as one of their first mods. So - you'll still have to keep the long line, but it will need to be plugged or you will have a vacuum leak there that may affect the function of the vent controls (but it won't affect the motor in any way, since that check valve is in place on the shorter line there's no way a vacuum leak at the heater controls can alter the smooth running of the motor).
Make sense? Hope I helped!
Last edited by camaronewbie; Oct 10, 2009 at 09:33 AM.
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