Well I never

[jdlexus]

You learn something new every day.

The engine overheating signal flashed up and the temperature gauge got into the hot area. I always check the coolant regularly.i thought the coolant tank on the right side in the engine bay was the one for the radiator not so appently it's for the hybrid system . the header tank for the radiator is under a trim on top of the radiator if you didn't know you would never guess as it's well hidden.

fortunately my local mechanic new where it was and filled it up.so no damage done I can now check this regularly. 😀👍

[ColinBarber]

The question is why was it low, it shouldn't drop at all. Possibly your water pump is leaking, otherwise a hole somewhere in the rad or pipe.

[Greisingel]

Happened to me. A thin vertical white line on the left top shoulder of the radiator spoke of a crack that opened under heat and expressed pressurised boiling coolant/water.

Radiator change. Or as CB says, pump needs a check. Get a scope down the belt area and look for a fan of purple spray, leaked coolant.