My upper radiator hose was flat so I changed it. In doing this I noticed I had no thermostat.?

My friend said I don%26#039;t need one in Florida. The coolant was fine in the radiator. Two days later I noticed the hose was flat again.My temp light in the normal range. What could be the cause or what should I check next? Could the radiator cap be bad.|||the reason your hose goes flat is.... when the coolant cools down it contracts... it should relieve this pressure difference by drawing coolant from the overflow tank. You need to replace the radiator cap. Now... the thermostat... you defiantly need one. without a thermostat the engine will not cool properly as they are not only used to regulate engine temp, they restrict coolant flow so it picks up the heat... they cost less than $10... change it, replace the cap with new and you should be good to go! hope this helps.|||cap could be bad but you need a thermostat so your car can run at normal temp|||Yes it could be.