My car had a moment today the temp went up in down while idle.Once the light turn green it went down.2hrs later i open the hood i notice the coolant reservoir tank is way over the limit.so i open the radiator cap and put some inside.New radiator new water pump new temp sensor and fan switch.Both fans come on and new thermostat.Any ideas?

 

Head gasket.

A combustion leak test can confirm.

 

i had a feeling well time to sell it....