little black box leaking coolant

[tahoe nick]

97 5.7 vortech.little round shaped box(plastic) that has a vacuum line coming outthe back running to some sort of sensor on the firewall. The underside has a plunger? That has metal arm hooked to it. Its close to the bottom of the coolant reservoir (for reference of location) its leaking antifreeze (sometimes) and my radiator,which is brand new, will not stay completely full

 

[MO Viet Vet]

First thing I think of is a heater control valve. How many coolant hoses attach at it? Is it just a vacuum hose and that is it? Rock Auto shows a valve with hoses attached or a heater valve solenoid that has 1 vacuum line and has electrical plug.

 

[tahoe nick]

Itseems to be a junction of two main hoses, one of which goes into the block. the smaller,vacuum_ like house goes to the firewall and connects to some sort of electrical device/ sensor .I can move the plunger in and out as long as the engine is not running.

 

[MO Viet Vet]

I would say it is a heater control valve but is a different one than I see at Rock Auto. What you are describing sounds like the heater control valve and if leaking coolant then the radiator will keep going down because will leak worse when engine is running and creating pressure.

 

[tahoe nick]

Thanks. It seems like when it has pressure on it and the plunger is pressed in , it leaks. But so far, the radiator hasn't went down any more. But the last two times I filled it , it went down to the same level.When the engine isn't running , the plunger is freed and I can move it in and out and hear air ??? Also it seems to leak right when I start it up

 

[adam74]

its a vacuum controlled valve. opens/closes depending if you're running the ac or heat. that sensor controls the vacuum. check the hoses first for leaks then check the valve. I would definately replace it if its the valve itself leaking.