On 9/7/13 I purchased a Honda Civic 2003 for my car. All appeared to be on with the car, ran a test drive seemed to be fine, no leaks so it is a done deal. We find out shortly after the car is overheating. We took it to a mechanic and they said the head gasket needs to be replaced. We replaced the gasket, we replaced the thermostat twice, we replaced the oval reservoir since the cap was missing. Initially, after fixing the gasket the car worked for about a week. The mechanic did mention that the o2 sensor (I think that was the name of it) on the car needs to be replaced and that is why the light is on in the car. He mentioned it needs to be replaced but there is no rush for it. A week later it is over heating again we called mechanic and ended up replacing some things. The mechanic hooked up car to machine, tested fans and all appears to work on the car when he is testing it. He drove the car 5 - 10 minutes it works. My son drives it 30 minutes and anti freeze is on the hood and the grill. I am not sure what to do next. We have not changed the water pump and or the radiator. The mechanic wants me to leave car with him for a week so he can drive it , he is not sure what he will charge. I am clearly annoyed since my son and I worked so hard to buy this car out right. Please help!

When he changed the head gasket, did he also machine the head and check it for cracks? This should have been done as part of the repair and if it wasn't, it's possible that there is a crack in the head causing this problem.

According to him it was all checked. I know he had my car for 8 days he had to wait for the head gasket since it was sent elsewhere as I understood it.

It's important to follow the exact procedure for draining and filling the cooling system in the Owner's Manual--they do vary and it's very important. Failure to do so can result in a warped head, blown head gasket, and the engine seriously overheating.

A friend of mine, who owned his own auto repair shop for years, inadvertently blew the head gasket on his daughter's 2000 Civic LX, D16Y7 engine, by not properly refilling the cooling system after he replaced a cracked radiator. After we replaced the head gasket, milled head, water pump, and timing belt, he was ready to do it again by not following the instructions in the Owner's Manual on how the properly fill the cooling system. After I told him to stop and check, he found out that he needed to turn the ignition switch to ON and electronically open the heater core control valve to prevent a major air pocket from forming in the cooling system. This might be your problem. Unfortunately, the head gasket may have blown again.

I agree with TxGreaseMonkey (not to imply that I am in his league in this field). But I have read those instructions for refilling my vehicles over recent years and I always wonder about how many mechanics get into and follow those very specific details for every car they get involved with. It is difficult to discuss with mechanics because you don't want them to think that you are questioning their skill.
If you can't do the work yourself, the only option is to find and hold onto a mechanic who has given you good results.
I'll get off my soapbox now.

Thank you for letting me know the importance of refilling the coolant. I have not changed the water pump, the timing belt or the radiator. Do I complete those first and then if those don't work the head gasket? I guess the question then becomes should I have to pay to have another head gasket job done again? The mechanic charged me additional for all fluids added to the car. Evertime, it has overheated he refilled it. I am sure he would not be willing if this is the case to bite the bullet on this. I am almost certain he will say it is my son which would equate to a new head gasket and this quite frankly is not inexpensive. Ahhhh, is there a tutorial for me and my son to do it ourselves AKA a mom willing to get her hands dirty.

This is not a job you can do yourself. For one thing, there are a number of specialized tools required. What kind of warranty came with the work? It was his responsibility to properly refill the cooling system.