The infamous test of leaving the car sit overnight. If the hoses are still hard next morning it is usually thought a cracked head. I have no ideal how good a test this is. Yet it seems to be used on the 603s.


For one if a cooling system where not tight the pressure could be released. Still if you were going to purchase one of these that is a test that is used. Why it would be specific to a head crack over a head gasket has always made me wonder.


Normally as the coolant cools the hoses go soft over time.