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A hopefully easy questuon


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 Hello Folks...New guy here

  I recently purchased a 1985 720 king cab with a 2.4z and a blown head gasket. Thanks to all the tips on here,the repair has gone smooth. This is my first foray into these small trucks so my experience is limited.

  While doing the said repairs I broke a part on the intake manifold.  I have since found out,this part is called a ported vacuum switch and is threaded into the intake manifold just before #1 cylinder and has 3 vacuum lines attached. I have been unsuccessful in finding a replacement and am hoping epoxy will hold.


 My question is. What does this critter do and how important is it? Can it be plugged and not have any adverse effect on engine function?


  Thank You in advance for any direction you can give me.

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Probably the T V V (thermal vacuum valve) it has three hoses on it and located just to the front of the carburetor on the intake. Sound right?


It's job is to leak air into the vacuum advance line to the distributor when the engine is cold. In effect the timing will be retarded when engine is cold to reduce emissions. When the coolant in the intake warms the V V T it, closes the air bleed and full vacuum advance is passed on to the distributor for full advance. There is a similar bleed in the same V V T for the EGR so that it can only operate when the engine is warmed up. Removal or disconnecting it will just give full advance all the time. 


The top hose goes to the air filter to supply clean air to the two vacuum sources below it. The next hose down goes to the EGR. Leave this hose open to the air and the EGR will be deactivated. (don't need it) The bottom hose goes to the vacuum advance. Plug this hose to preserve and keep vacuum advance. (you need this)






Welcome to Ratsun.

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 Thank you sir. That is exactly the part I was talking about. The top and bottom stems were broken off. As of right now,I have epoxy drying for the fix. If I'm not happy with the fix,and I understand you correctly,I could remove and place a plug in the manifold and leave the top two hoses open and plug the bottom hose?


  Thanks again

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