I'm trying to determine if the Thermostat Housing is leaking on my 2005 Cooper. There are no obvious signs, but if I squeeze the upper radiator hose, I hear a slight chirp from the vicinity of the thermostat housing. Replacing the cap had no effect. Can anyone tell me if it is normal to hear this sound when squeezing the upper hose? Unfortunately, I don't have access to a 2nd MINI for comparison.

Thanks!