Radiator OK?

If you are SURE about the pump and the thermostat, and I would not be
sure about them if I were you, your choices then come down to a clogged
radiator and a clogged block.

How did you check the pump and the thermostat?  If you put your hand
on the radiator, does it get warm?  Does it get warm in some places and
not in others?

If you disconnect the bottom hose from the radiator (cold, obviously),
does water pour out of the radiator or does it slowly trickle out?

Has the water pump ever failed before?  Water pump failures that leave
debris in the system are a big issue.
--scott

What's the history of the car's cooling system service?  Did you just change
the coolant?  It's possible to considerably underfill the system if you fail
to follow procedure.  Also, with a 12 year old machine, it's possible the
water passages are blocked by the accumulation of corrosion in them.

If the system's been bled and full to capacity, it might be door number two.

BMW used to recommend coolant change every two years from manufacture date.
It's now 4 years, but I suspect that's a nod to the cost of "free"
maintenance, not a change in the vehicle or coolant properties.

Over-the-counter coolants are not recommended and can contribute to the
problem.  So, it's possible a failure to change the coolant frequently or
with the wrong coolant has clogged the cooling passages.  Given the
difficulty and expense of fixing the problem, I'd check and recheck
everything else first.

R / John

hi there guys,many thanks for yout replies,i do appreciate the
concern.believe it or not it was a massive airlock in the system.i had
always been lead to believe these bm.s could be real pigs to bleed but
felt i had done everything right. i decided to persevere with bleeding
trying a couple of differant methods and sure enough after 2 days of
trying,i blead her succesfully and have since had no probs
whatsoever,thanks again!!