Hi gang, got a bit of an issue with the wife's Focus.

It's a 2014 1.6 diesel, car is running fine and gets up to temperature ok, right until the cabin heater is turned on...with the temperature setting at half way on the dial ,the temp' gauge on the dash sits at the mid way point but when the temperature dial is set to warm , the dash gauge drops down to 60° mark ( cold) and there's no warm air from the vents.

Unfortunately I don't drive the Focus very often and have no idea how long it's been doing this .

I have checked the header tanks and while the engine was warm the header tanks was empty...but when I opened the cap  it released the pressure and the coolant level came back up but only to the minimum level.

Now I'm no mechanic but do have a little knowledge and was wondering if the cause could be as as simple as replacing the coolant 'stat .

Has anyone else had this issue,of so how did you cure it ?

TIA 

The empty header tank refilling means there must be air in the system.  It may just have got sucked in due to a low fluid level if it hasn't been checked regularly.  But in most cases will mean a small crack or pinhole in one of the components.

It may also need a new thermostat, but I wouldn't expect that to be the main issue in this case.

Thanks Tomsfocus,

have had a quick look round the engine bay , there is a trace of coolant seepage around the 'stat housing , which hopefully a simple fix