Do I need this "T" in my vacuum lines or should I run lines individually?

[jcook100]

I am working on replacing my vacuum lines in my 1991 4.0 and have a question.

I see that there is one line coming from the octopus/tree that splits into two: one for the blend door and one for the vacuum canister. I can't tell if this was deliberate/stock or some jerry-rigging by a previous owner.

When I replace these lines, should I keep the T junction or run individual lines back to the octopus/tree?

 

[franklin2]

You need the tee. In the main supply line from the engine tree there should be a check valve in the line. Normally vacuum is applied through the check to the tee, where it supplies the HVAC in the cab, and also stores vacuum on the vacuum storage canister.

When you pull a hill and open the throttle, the engine stops producing any significant vacuum. The check valve in the supply line will hold the vacuum after it in the tee area, and it lets the vacuum canister take over and supply vacuum to the HVAC for the short time the engine is not producing vacuum.

If you do not have this feature, each time you pull a long hill your heat or A/C can go to the defrost vents. Then when you stop putting a load on the engine, the vents will go back from defrost to where they were originally. 4 cyl trucks are especially bad about this, since their throttle is open more.

 

[jcook100]

Thanks @franklin2 . So, when replacing the lines, it seems like I need a check valve somewhere along the main supply line and BEFORE the T. Is that correct? Are these valves easy to find? I have not heard of them before.

 

[Broosedamoose]

You should have one there already as that's the stock set up.

 

[holyford86]

the tee should be the check valve if memory serves me right

 

[Kira]

"the tee should be the check valve"

Then it's a part with a number; not just a tee, no?

Is the small premium for silicone worth it?