Coolant leak on 2005 Toyota Corolla

Hi,
Car has 106,000 miles on it-I just moved to Seattle from San Diego and drove several hours in 104 degree heat with the car fully loaded. Went to change my oil and found that coolant has leaked out of reservoir and splattered onto engine. The car has NEVER overheated-there is still coolant in the radiator. Oil is clean. We purchased a new water pump and are about to replace-does this sound like we are on the right track? Serpentine belt is new. Tensioner pulley will be replaced with water pump.
Thanks!

Asked by for the 2005 Toyota Corolla
I wouldn't replace the water pump unless it is leaking, or the impeller on the pump was bad.
This was caused by either high pressure in the cooling system or the pressure cap is failing to hold the correct pressure. High pressure can be caused by overheating or a leaking head gasket.
If the engine is not overheating, then it's possible you have a bad reservoir cap. I would get the cap tested, but also have the engine checked to see if the headgasket is OK.
Let us know what you find out!
Good Luck and enjoy Seattle!
2 answers
I would get the coolant system check before making any repairs