VR6 overheating

I've had my vr6 for nearly 6 months now, was just away to sell it.
When a boy came down to look at it and asked if the head gasket was ok which i told him fine, he then proceeded to take the cap off the expansion tank whilst it was hot,to check if there was pressure, since then its started overheating maybe just a coinsidence i dont know,once it gets hot the coolant would come out of the expansion tank. Took it to the garage, they changed the thermostat and checked the radiator but it still overheated ( top hose to the radiator was hot but bottom hose was cold ). The garage said it would be a blown head gasket so set about the job, when we got the cylinder head it bit look a bit shabby so decided to get a second hand cylinder head finally got it all put back together but the same problem still occurs, could anyone help, cheers!!!

I've had my vr6 for nearly 6 months now, was just away to sell it.
When a boy came down to look at it and asked if the head gasket was ok which i told him fine, he then proceeded to take the cap off the expansion tank whilst it was hot,to check if there was pressure, since then its started overheating maybe just a coinsidence i dont know,once it gets hot the coolant would come out of the expansion tank. Took it to the garage, they changed the thermostat and checked the radiator but it still overheated ( top hose to the radiator was hot but bottom hose was cold ). The garage said it would be a blown head gasket so set about the job, when we got the cylinder head it bit look a bit shabby so decided to get a second hand cylinder head finally got it all put back together but the same problem still occurs, could anyone help, cheers!!!
Brell, I had something close happen on my VR6GTI. It kept overheating, though the oil temp was fine. I'd fill the reservior because I couldn't find a leak, and a few hours later it would be empty again. I could smell a little antifreeze, so I took it to my mechanic. It ended up being a busted hose and pcv piping which you couldn't see from looking at the bottom of the car or top through the hood. He had to take off my front bumper to repair it. Stopped the leak and everything is well. Hope this helps.