Someone back me up on this one, My grandpop taught me this trick a while ago for checking for a bad head gasket.
With the engine
cold, get a helper and have them fire the car up while you are squeezing the upper radiator hose. If you feel immediate pressure, then you have confirmed that combustion gasses are entering the cooling system.
If the system builds pressure slowly as the engine warms up, then the head gasket is good, or has a small leak.
I don't know if this method is only good for indicating larger leaks or what, but it's worth a try.
Just, someone back that up before anyone relies on my information. If im wrong I'll edit my post. Heck, Im kinda curious if my grandpop was right anyway
.