I have been trying to install a coolant filter and in there pictures it shows this vacuum valve (I think) next to the oil filler. The valve has a line coming in the top, on the firewall side. And a nipple for a line coming horizontally off the front, in the center of the round part, but no line, at least on my truck. But in the photo it shows a gray line connected to this nipple.

What does that valve or whatever do? And should I have a line there?

 

Vac valve is for the heater control. On mine the heater supply hose comes from the front steel tube to a rubber 3/4" hose about 8 inches long, to the heat control valve, then to the fire wall. the valve has a black plastic cap facing the fire wall with a small vac line in the middle of it. I put the filter tee between the steel tube and the heat control valve. Hope that helps

 

that vac line comes from the fire wall by the heater hose. I can always look at mine if that will help and give you clearer info.

 

On mine there is a vertical line on the firewall side of the valve. But the nipple on the front, in the center of the round valve is empty. I think a vac line should be there, but I cannot find a loose one anywhere.

 

Is there supposed to be a vacuum line there?