Over heating

May be a head gasket problem. Sounds as if there is a breach in the gasket allowing compression pressure to pass into the cooling system and over pressurizing it causing the blow back. You can get a simple chemical test to check for this most mechanics can do it in a few minuets. Secondly, if you fill the coolant up with water, right up to the top and leave the filler cap off, the engine and watch the water level, it it bubbles a lot and surges blowing coolant out when you open the throttle and then back off this is a fair sign there is a head gasket problem. This needs to be done with the thermostat open so caution will be needed as it will be hot! Best option is the head check first.