Hi all am new and hope anyone can help I recently bought a focus 1.4 cl ok its a good car naff engine I bought the car with a misfire and found it was ht leads and has been running well. But lately I have noticed the temperature gauge fluctuates it as always sat round the halfway mark solid but now if I go round a corner or up/down hill the gauge drops then goes back up. It's never overheated the heaters work brilliant.

I've replaced the thermostat with a ford genuine one (expensive) still no change flushed cooling system no change.

I've noticed at idle or if leave the car running the bottom radiator hose is warm but I took car for a 20 min drive came back and checked hoses and found the bottom hose was cold and the radiator was same temp as top hose quite hot. So again checked thermostat and was opening correctly . So I've no idea what the problem might be. Hope it all makes sense and thanks in advance

Just update I used dash test to monitor engine temperature and it reaches 86 degrees max but it's fluctuates between 86 and 46 degrees when driving thanks again

Sounds like you have air in parts of the system.

Or you placed the thermostat in at the wrong orientation. The air valve gold looking price should be at top, this helps get air out.

Or it maybe the sensor but you should test it first before replacing.

I bled the system as per ford says and thermostat it placed correctly am wondering it may be an electrical fault as I've noticed as well as the temperature gauge the speed seems to be 5mph out. And fuel gauge seems inaccurate I put £10 of fuel in yesterday I left tesco and gauge was just shy of quater of a tank I've covered 15 miles normal driving between 30 and 50mph no thrashing and the gauge read this morning just above 1st white line and fuel light is on.so my focus 1.4 is doing 15mpg there are no leaks as I've checked and on dash test am getting dtc code d262 don't know what it means sorry for long post