How much should I be looking at to replace a heater cap?

Had to call out breakdown recovery twice on Friday as smoke was coming out from under the bonnet. The first call out repaired the heater control valve outlet which had snapped with a new hose/pipe but it meant that hot air would be turned off.

Same issue with smoke about 10 miles into my drive home. Opened bonnet, there had been a big leak. Called out recovery again who on further inspection found another pipe has come away. Was just about able to make it the next 15 miles and was advised to get to garage as soon as possible. Does this sound like it could be more than the heater cap.

Car is a ford ka if that helps.

That heater control valve is known to be troublesome. Personally I'd be looking at renewing the valve plus any pipes that seem iffy. Then refill the coolant and bleed the system. If you're not sure get a good mechanic to sort it out.

Hi so over time the radiator cap has spring in the inside which can become weak over time. This cap is a pressure cap it maintains the coolant system at 120 degrees C. Higher than boiling water at sea level to make the car more efficient. So over a period of years does need replacing.

I'd replace every hose for starts.

I'd have a qualified mechanic check the entire cooling system: radiator flow, water pump, belts, etc. You may have a circulation probem. Worrisome: that there's a head gasket leak with combustion gases and pressure entering the cooling system.

A radiator cap? If you're blowing coolant all over the place you may have a bad head gasket.

The car is very much damaged after driving it overheated. Let the mechanic see how bad the situation is. We can't.