I cannot drive it.  Engine too hot.  Gauge in red after 5 minutes.  No
steam.  Residual oil smoking a little because it is so hot.  Yet
Radiator is ice cold.  One hose is warm.  I have since taken it apart.
 Thermostat is missing.  Inside of water pump looks good.  Rotates
smoothly.  Belt was tight.  Fan spinning.  Poured water into radiator
top hole and it flows right out bottom hole.  Water is nice color of
green.  Hoses do not appear to be clogged by squeezing outside. 
Plenty of water was in plastic water reserve tank next to radiator. 
Full to top line.  When I took off reserve cap it exploded all over. 
It was under pressure.  When I took it apart I spilled at least a
gallon.  How do I know if the radiator itself was full or empty?  What
is my problem?  What experiment should I do next?  Do I have to put it
all back together for the next test?  How does water get from reserve
into radiator?  Help!

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Request for Question Clarification by scriptor-ga on 27 Oct 2005 18:55 PDT

With such serious problems, you should see a licensed BMW mechanic as
soon as possible.

Regards,
Scriptor

I am not a licensed BMW mechanic, but cooling systems are fairly
simple. I will guess that your radiator was empty. Coolant only flows
from the overflow tank into the radiator when the system cools and a
vacuum exists. There are several ways for the cooling system to become
empty.
1. A leak in a hose, the radiator, or the engine block.
2. Blown or leaking freeze plug.
3. A blown head gasket leaking into the combustion chamber.
4. A blown head gasket leaking into the crankcase.
I will bet that you have one of these situations.

I am not a licensed mechanic either. I assume you dont want to spend
the amount of money a liscened mechanic would charge.
    Another way to loose coolant is through the waterpump (gasket,
bearing, etc.)(probably not the problem). It could be the headgasket.
check your dipstick, if the oil looks normal probably not leaking into
the crankcase. If leaking into combustion chamber should see white
"smoke" out of tailpipe. any other leaks will fallow gravity. check
the ground.Bleed any air out of cooloing system.
    I would check to see if you have coolant returning to radiator
from motor(drain the system, save the coolant, use water while testing
as it won't harm the enviroment. There may be a clog in the
engine(what I suspect), wihout the thermostat you should be able to
tell as soon as the car starts. If no or low flow check for flow out
of waterpump also should be able to tell as soon as the car starts. If
low or no flow replace waterpump. good flow = clog in engine. If this
is the case you could try forcing the obstruction out by hooking the
outlet from water pump to the engine via the return hose so the water
flows in the oposite direction throuh the engine. same preasure so it
should not do any harm and mite clear the clog.

Hope this helps.

You probably have a headgasket leaking from the combustion chamber
(cylinder) into the cooling jacket (areas where the coolant flows
around the engine to keep it cool). The massive amount of heat and
pressure from the un-contained explosion in the cylinder is
overwhelming the cooling systems ability to contain it. A "sniffer"
test will determine whether you have carbon-monoxide gases leaking
from the cylinder into the coolant- they use a chemical detector to
sniff at the radiator fill neck (where the cap normally goes). A good
shop will have this tool and know how to use it... most radiator shops
particularly. Good luck.