vacuum canister

[garyweb3]

Is there a way to test this vacuum canister to see if it works correctly? Thanks.

[Htchevyii]

IF you have a vacuum pump, just cap the other nipple and see if it holds vacuum. I suppose that you could pressurize it with a rubber tipped blow gun at relatively low pressure and listen for air leaks or dunk in in water, you'd probably have to hold the cap on the unused nipple while doing this.

[Eagle_SX4]

One of the ports has a check valve on it. That is the one that gets hooked up to the manifold. The other one is open and will not hold vacuum. 

 

To test it pull a vacuum on the port with out the check valve and it should hold vacuum with no cap on the port. 

 

If you can't get it to hold vacuum on either port the check valve is likely bad or the canister has a leak.

[pizzaman09]

7 hours ago, Eagle_SX4 said:

One of the ports has a check valve on it. That is the one that gets hooked up to the manifold. The other one is open and will not hold vacuum. 

 

To test it pull a vacuum on the port with out the check valve and it should hold vacuum with no cap on the port. 

 

If you can't get it to hold vacuum on either port the check valve is likely bad or the canister has a leak.

Is this check valve arrangement also part of the larger football vacuum canister?  I wonder if I hooked mine up incorrectly after installing cruise control.

[Eagle_SX4]

3 minutes ago, pizzaman09 said:

Is this check valve arrangement also part of the larger football vacuum canister?  I wonder if I hooked mine up incorrectly after installing cruise control.

Yes, there is a check valve in all canisters with 2 or 4 ports. The single port canisters do not have a check valve and one needs to be added into the system to prevent vacuum bleed off.

[garyweb3]

The port with the larger rubber hose attached is labeled VAC. Is that the port that has the check valve in it? The smaller left port had a plastic hose to it.

[A-man930]

Glad I stumbled upon this; had no idea there was a check valve inside.  

[Eagle_SX4]

On 12/25/2025 at 11:29 AM, garyweb3 said:

The port with the larger rubber hose attached is labeled VAC. Is that the port that has the check valve in it? The smaller left port had a plastic hose to it.

My guess is that is correct. I have not had any of the smaller vacuum canisters to test. You could try hooking up a vacuum hose and blowing into it. If you can blow into the port then it doesn't have a check valve and then try the same with the other side. 

 

Which ever side you can blow into does not have the check valve and should be hooked up to the HVAC controls. The other side should be hooked up to the vacuum source(intake manifold).

[garyweb3]

I blew into both ports. The one labeled VAC must have the check valve because I could not blow into it. The smaller port I could blow into. So why is the port that I could not blow into labeled VA? I haven't traced out the hoses yet.

[Eagle_SX4]

4 minutes ago, garyweb3 said:

I blew into both ports. The one labeled VAC must have the check valve because I could not blow into it. The smaller port I could blow into. So why is the port that I could not blow into labeled VA? I haven't traced out the hoses yet.

By blowing into the port you are creating the reverse flow of the vacuum. Which means that your check valve is working as it should and not letting air into the HVAC controls. The VAC side of the canister should be hooked up to the intake manifold.

 

The check valve was used to help keep the HVAC controls in constant vacuum. So they would stay put while under acceleration and not go to the defroster which is the default position when there is no vacuum.

[garyweb3]

I traced the hoses today and the one that goes to the VAC port does indeed go to the intake manifold in a round about way and the other ports hose goes through the firewall into the cab.