2004 Mini Cooper S overheating

[ccannedy]

My Mini Cooper S is overheating and I don't know why? I turn on the the car and let it Idle. After 10 min the overflow tank starts to boil making a popping sound. The temp guage starts to rise and I shut it off. I changed the thermostat didn't work. Took the head off and the gasket looked new. I had the head checked and it was milled and didn't have any cracks. The head got the OK from the head shop. So I put it on, and it still did the same thing. There is no water in the oil and nothing coming out the tail pipe. There is no leaks at the water pump. I checked the radiator next and its OK. What can be causing it to overheat?

[oldmanward]

my eaton s/c is going toes up, so i was doing some research and the water pump is driven off the back of the s/c and the gears get worn in-turn it stops working. theres a fork that is mated to the pump that can go kaput and inside the "eternal lubed & sealed not ez to get to and not meant to be checked"(frustration) there are gears that spin that fork. the shaft seal goes bad and the "eternal lube" gets cooked out and wears out the gears that eaton doesn't make replacements for (thats where im at)
thats my guess and $0.02

[Partsman109]

The water pump drive is definitely something to check, but that condition usually makes a nasty racket which the OP does not mention.
There is also no mention of bleeding the cooling system after the thermostat replacement or cylinder head R&R...and if it was done, was it done correctly? The procedure is kind of a pain.