Is the heater valve in the supply line to the heater, or in the return line back from the heater? How do you get at it?
Haven't noticed the obvious signs of leakage inside the passenger compartment.
I was hoping on the tank cap, as I've heard that they have been known to leak. It wasn't.
All the other things were definitely leaking and needed replacement. The radiator and water pump were last summer, the auxiliary water pump last week. I replaced the attendant hoses for cheap insurance.
I took a 200 mile trip Saturday and it lost about a half liter of coolant. Not low enough to alarm, but obviously below normal level. I checked the level prior to leaving on the trip.