Grab your Turbo Torch and a IR gun or spray bottle of water or be a man and use your hand. Go to the receiver and begin to torch about a 6" vertical section of the receiver, preferably starting from the bottom up. Now Pull the torch off and use your IR gun on the receiver from the bottom up, where ever there is liquid present in the receiver it would have removed the heat that the torch applied. but where the liquid level stops and only vapor exists, the receiver will be MUCH hotter. Or use a spray bottle with water. Torch the receiver and spray the receiver from the bottom up. the water will hit the receiver and dribble down until you get above the liquid level and only vapor exist, now the water will start to sizzle. Or MAN up and torch the receiver and use your hand...where ever liquid is present the receiver will be warm. but once you get above the liquid level and only vapor exist, you will feel the heat.