I purchaced an '03 Cooper S back in May and it's been great. About two weeks ago I noticed a coolant leak at the inlet side of the radiator where the neck bolts on. I took it apart and replaced the o-ring. About a week later same thing. I flushed the coolant and tried to purge the system but only getting air w/ very little to no coolant, and it ran for roughly an hour w/ the fan running the enitre time. The inlet side of the radiator gets pretty hot and I'm guessing that is why the o-ring is failing. Radiator doesn't appear to have any build up in it and the engine doesn't run hot. Coolant appears to be circulating thru the system but still getting air. Is this normal on a Mini? Are there any known issues with the wate pump impeller? I've read the issues with the drive gears but I don't have any noises to speculate that being the cause. I may be overly paranoid about it but don't want to take any chances and causing a more $$ly repair. Any ideas or suggestions will greatly be appreciated. Thanks

 

Not sure it relates at all, but thought I'd offer it:

I had to have the radiator in my 2003 Base R50 replaced around 50k miles/ 7 years of age. It showed no signs of typical age or deterioration, yet it started to come unbonded across the bottom (where the fins and pipes meet the base of its body). Perhaps there was a bad day of bonding these together at the factory 8 years ago?

 

It is pretty common to have the plastic sides come unbonded to the metal middle..
They are only crimped...desgin weakness/common failure point. New rad is not too $$...
The car is getting old enough that the orgional thermostat, hoses, and pump could all be suspect, especially if it was not regularly matained...
Saying suck air in....the system is matained at a few psi to increase boilover protection...it should be airtight, and if anything, push water out...
Getting the air out is tuff...the shop i saw the bad radiators getting swapped out uses a preasure bleed system on the just a coopers....
On an s, bleeding can take a nit for the diy...
Having air in it will cause it to overheat...the bottle on the s is preasureized, and often leaks...
did yoi open both bleeding valves? One ny the rad...one hidden near the thermosta is i remember right...