ford fiesta mk4 zetec overheating problem

Hello

could you please help me fix my zetec, when I drive it the temperature gauge rises to the red with my heater blowing cold air then after a while hot air will flow then the temperature goes back to normal this keeps happening everytime i drive it.
I have had a new radiator cap and new thermostat fitted also someone bypassed the heater valve with two pieces of copper pipes but still have the same problems. been told maybe air lock but cant seem to get all air out. parts on order are temperature gauge sender and then maybe temperature gauge,

I am not familiar with your particular vehicle but, have had similar problems with some others. Your symptoms, ie, the heater blowing cold and then back to normal, do seem to suggest that there is air in the system, especially with the modifications etc which you have already carried out. These modern cooling systems are quite complex, with many areas (heated manifolds, heater feeds etc) allowing air to be trapped. I have found that draining and then re-filling the system VERY slowly, (at least five minutes with small amounts of coolant at a time) and with some squeezing of the top and bottom hoses, will help to get rid of most of the air. Fast filling of the system, does trap air within the system but, when filled slowly, the air can find it's way out.

another way that usually works is to run the car with the expansion tank cap off, and keep the bottle filled right to the brim.
When the thermostat opens water will gush out over the top of the bottle. When it does, turn off the engine and top up the bottle if needed.

run the car engine

go into car and switch heater to maximum heat

put fan full on for 15 minutes

this will purge air out of system