Air lock in coolant system?

Hey guys,



Picked up an MG ZR 105 yesterday, 12 months MOT, Headgasket done just before the MOT, replaced with an uprated one, and the head skimmed, only driven about 10 miles since the test! I picked it up thinking it was a perfectly working car.



BUT after about 10 miles it started making a noise I'd never heard before, almost like something trying to scratch up through the bonnet, so I stopped in at a garage when I saw one and had opened up the bonnet, the noise was the coolant boiling in the expansion bottle. At this point the car wasn't overheating at all.



The garage opened the tank, let the pressure ease off, noticed there was no water whatsoever in the tank, for about 2 mins, until it became full again, then low again. So they filled the tank up again, and left the engine running with the lid off, the water just started spitting out of the tank, so I turned it off, filled it up, put the lid back on, and went on my way having been told it was either the headgasket having gone (again?) or an airlock.



Then I noticed I was getting no hot air through the vents (one vote airlock), but soon after leaving the garage it DID start overheating. A lot. I was stopping every time it got to red and letting it cool down.



I get no warning lights on the dash, just a lot of heat and A LOT of steam from the cap when I take it off, also it can idle a bit nasily when hot, and try to stall.



Questions are,



If it is a lock, how much would a garage charge to sort this out? (last mechanic I spoke to assured me that there isn't a bleed nipple, it just bleeds itself over time :S, but others seem to think there is one)



Does this sound like an air lock, and could driving with an airlock damage my car more?



Either way I think I'm just going to sell the car on again for a disgustinly low price and cut my losses, especially if its HGF again :(

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