Header tank cap seperation

its in the header tank providing my memory serves me correctly ,could be underneath in the header tank out of sight .You do mean the level sensor and not something else as the temperature sensor is in the head on some earlier models .

will assume it the newer mini produced


yes 20 minutes is too long

will need to go to a workshop for inspection
possible answers for the issue

the fan .......all fixable
faulty internal thermostat ..
faulty thermostatic temp switch not switching off
of fan motor not spinning quick enough


the fan thermostatic on /off switch is set that way to cool down the motor and not warp the head or block
after stopping the engine the coolant is at is hottest for a short time
so the fan shuts off when the coolest temp of coolant is reached

header tank needing top ups

check for hose leaks at clamps or small cracks in heater hoses
the cap of the header tank may need replacing
the internal heater radiator may have a leak
(you would have wet carpet inside the car)
a welsh plug may be leaking
radiator may have a hole hole
or other coolant leak unknown

worst case
if the coolant in the header tank looks like it is sludgy
(has oil in it ) or oil dip stick has coolant or water with the oil
there is a possibility the head gasket has blown

mini cooper
thermostat housing one part

Usually on bmws header tank is located at the side of the radiator where the cap is to refill coolant system

It's normal

remove header tank cap undo drain plug at bottom of radiator and bleed screw at top of radiator once all coolant has drained retighten tthe drain plug pour the new coolant into the header tank waiting for the coolant to drain through system and watch for coolant to come out of the bleed screw , shut bleed screw top up the header tank to the max level replace cap.Now run engine ,dont drive just stay with revs at 1500 open bleed screw to let any trapped air out and wait for the cooling fan to cut in , allow engine to cool down and refill header tank if required and repeat the running/bleeding/fancutting in procedure until when engine has cooled the coolant is near the max mark on header tank

indicates a blown head gasket
have a compression test done
then check for thermostat stuck closed and blocked radiator cores

You need to push down on the cover to get it to turn past that last partial turn. It is a safety feature to keep caps from blowing off inadvertantly when hot when an inattentive person starts removing cover.

it will get worse renew the header tank ,or to you the plastic compartment

Check your bi turbo charge pipes for positive leak

if the coolant light is on or comes on when driving you MUST let the car cool down at lest 1 hour before doing anything, after this cool down time lift the hood [u.s.a.] or bonnet [uk] looking from the front of the car on the right hand side towards the back of the engine compartment is the coolant header tank,about 5inch square black in color [u.s.a.] colour [uk] with a large screw top and some rubber pipes coming from it,this should be topped up with coolant right to the neck of the screw cap when you remove the cap to top up the coolant unscrew it slowly as it may be under pressure you don't want hot 212F[u.s.a.] 100C [uk] coolant in your face do you.good luck.