Recently I've had problems with my mustang overheating, I took it into the shop and they pressure tested it but said they couldn't find any signs of a leak in my system, they checked the head gasket and that was fine too. They told me that they thought it might be air bubbles in the system and they flushed it out. It's been about a week and now my problems are back and worse than ever. Any suggestions as to what else I should check?

 

If it's not losing water, check the thermostat.

 

Are your fans kicking on?

 

^^^Check those first. Also if the hoses are too old, they may collapse and may restrict or block coolant flow.