Car overheating going uphill Is my assumption correct?

Question

My wife has a 1996 renault clio 1.4rt automatic. It has started to run warm lately and gets very warm when going up hill. I have checked the pipes and they are all getting warm, the radiator is warm all over so i don't suspect a blockage. There is no water/oil mix on the dip stick and no buubles in the overflow tank (no headgasket problem). The car runs fine and the fan comes on it never getts in to the red the fan controls it "just". The coolent level reamins constant (no leak). The only thing i did notice was a slight hissing noise from the top of the overlow tank, it's not the cap but a small crack in the plastic overflow tank, could this be a case of the system acting as a vacum pulling air into the system. Am i right in my assumtions any advice greatly appreciated.

Answer 1

Any lack of pressure in the cooling system reduces the cooling capacity and lowers the boiling temperature.(for instance if you pull a vacuum on the cooling system it will boil at room temp.)  Also replace the thermostat as they are very cheap.

Answer 2

water pump may be failing, or the radiator needs to be flushed

Answer 3

Your assumtions can be possible and you try to check the thermostat may failed to open.

Answer 4

Check the belt that turns the water pump to see if its tight,radiator could be partially plugged and maybe have the ignition timing checked. A retarded timing will cause a loose of power and it also makes the engine run hotter.