Mk7 fiesta 2010 help needed please

[bruce_rob]

Evening guys

So I am having some issues with the water system

I think it may be an air lock 

I fill up the tank and get the car running, after some time the water level drops 

I fill it back up and the process starts again

This happens over and over

There is no sign of a head gasket failure 

No oil / water mix

The water pump sounds ok

I have changed the thermostat

Any ideas 

[Luke4efc]

How much are you losing and at what rate?

An air lock would eventually go away. If you wanted to be sure then fill the reservoir up, start the engine, turn the heater to full and fan to max. Then hold the revs at about 3k for a bit. If there's any air trapped it should 'burp' out.

If you've put a lot of coolant in then i doubt it's that. You must be losing coolant somewhere.

The tanks can be prone to micro-cracking (impossible to see, but does have a leak path). Also if the expansion tank cap has failed it can cause a leak.

[ssharple2001]

Or a heater matrix leak? Have you checked for wet carpets?