2006 WQ Fiesta overheating problem

[partychef]

Hi all

My wife has an '06 WQ Fiesta, purchased over a year ago.

A few months back the car was overheating, after looking around we found a crack in the coolant expansion tank. We got a new tank and installed it with no more issues.

For the last month or so the vehicle has been overheating again. It doesn't happen all the time, I could be driving to work on the highway with air-con on but when I come to a stop or slow down in traffic, the temperature gauge starts to creep up.

I have played around with a whole heap of different scenarios and it all seems to come down to using the air conditioner.

I have done a radiator flush

I have a checked the oil and there is no milky deposits indicating coolant in the oil, the coolant doesn't appear to have any oil in it either.

The radiator fan works fine, I think (it does come on when the temp starts creeping up but doest seem to make a difference)

I have tested the radiator fan by disconnecting the temp sender. When this is done the fan comes on

I have replaced the thermostat

I don't think I'm losing any coolant but when the car is running the coolant can go from maximum to minimum and once I turn the car off the coolant will start flowing through the top overflow hose back into the expansion tank

Most of the time when I start the engine and start accelerating I can hear what sounds like water gushing from the firewall on the passenger side, the floor is not wet. It sounds like it's going through a hose

When it does overheat, the top radiator hose is hot and the bottom one is cool


Any help would be much appreciated