So i had some antifreeze leaking issues so i had to replace some hoses but in doing so i noticed the long vacuum line that runs off the top of the heater control valve is not connected to anything. The car idles very rough and i have had two mechanic friends both look at it but can't figure out where it goes. If someone could please help me.

 

It should come out at the firewall, the interior heater switch open & closes that valve, so vacuum goes & out at the firewall.

 

JRambo, I also have the same problem. I've looked, but cant find where it goes into the firewall. The heater valve in my 89 IROC has been deleted and I had the vacuum line capped off. Somebody must have yanked it out when the car was at mechanic shop, not going back. Now i'm having ac problems (its in defrost mode).
If anybody can help us please do so. I've done research, but still cant find where excatlly the line should go thru the firewall.

Thanks,
Gerry

 

The line that goes through the fire wall is in the main harness, look at the harness where the auto trans dip stick is, in that area. You might have to strip back the loom to find it, then repair it. Get a vacuum diagram, there might be a one way valve that should be there.

 

That's one of the minor sub-harnesses; it's the one for the heat and A/C system. All the wires and vacuum lines for that system amd that system alone come through there as an assembly... that's generally how the factory does such things for optional eqpt.

As said, peel back the loom or tape, and you should find it in there.

 

Any idea where to find the diagram? I have looked online but no luck.

 

There's no "diagram" for that.... it's too simple to need one anyway. No useful info would be supplied there, except maybe the color of the tubing the factory used... which if memory serves is purple for the "supply" vacuum line, and either white or black (not purple in any case) for the heater control valve one.

 

JRambo, any luck? I'm gonna check on mine on Friday (day off).