possibly Head Gasket Failure:

Been told by my mehchanic the HG has gone on my uk 2000 scooby
was over heating the heaters are blowing cold until i rev it up past 4500rpm, also theres water being chucked from exhaust pipe
and the radiator bottle water rises to the top and chucks water all out

funny thing is when the AA guy turned up to tow it he checked it and said it was the water pump as some pipes were warm and some cold?
but he didnt carry out the compression test.
also he said the waterpump was a sign when i rev it they blow warm air through heaters,

is it possible for head gasket to go badly?

 

I would not take the AA advice on anything, Had the AA come out to tow my Evo as it cut out and would not start, when he tried to plug his computer into the diagnostic port i told him that it would not work as it has a autronics aftermarket ecu and it wont show up on his computer, he totally ignored my advice and carried on anyway after about 30mins he said that his computer would not pick it up

Anyway he decided to tow my car back to my house as they could not send a flat bed truck for another 5 hours , and he marked my front bumper, and broke a driveshaft towing it. Never would I use the AA again, bunch of idiots!!!

Get a compression test done, only way you will find out if its defiantly gone, no point guessing!!!