Cover the bowl with a clean dish towel and put it in a warm spot, such as on top of a radiator or inside a gas oven with the pilot light on. (bodyasmachine.com)
If a radiator makes a knocking sound, this may solve the problem: Place a level on top of the radiator. (amerispec.com)
and I plugged the tube that is on top of the radiator into that because I figure if the thermostat lets more coolant into the radiator than the radiator has room for it will have to overflow into the coolant reservoir. (mechanics.stackexchange.com)