please help me!!!

[c-tina]

Hello,
Please can smeone help me? I have a ford Fiesta Ghia 1.25 zetec engine V registration. it has been in the garage for 3 weeks and they cant seem to find the problem!!!
Basically they think there is an air lock in the engine somewhere and it makes it over heat, if the engine is revved then it cools down. the head has been tested and skimmed, the pipes checked, the water pump replaced and the thermostat is new. Any ideas? please help i miss my baby!