Just got back from a weekend in WV mountain biking. Gotta figure out where my coolant is going before planning this weekend. On the trip down, a little over a quart disappeared in 200 miles. Then another quart driving to mtn bike and back in the space of a mountainous 60 miles. Then about half a quart in the 200 mile trip home.
On the good side, looks like a new fan clutch kicked my overheating issues in the pants. No needle movement (I know, so what?) on the temp gauge the whole way down and back.
Seems like a head gasket loosing that much coolant would show milky-ness on the dipstick. You can't find a hose leak anywhere?
Have you done the Pesky Heater Hose yet?
Any *smoke* coming out the tailpipe? White maybe?