R53 cooling fan.
 

I know this isnt the first time something like this has been posted, but being new to the R53 family, i am a little concerned. I have a '03 R53 - Cooper S.

For the first time today, in the rain, my engine cooling fan stayed on for far to long. I have 135k on this vehicle and just replaced thermostat housing, and coolant expansion tank.

I heard this happens because the coolant can be low, this shouldnt be the case, considering the overflow was just flushed? And the thermostat housing was replaced.

Also read that it could mean the low fan is out? and sometimes the fans get "stuck". After about an hour, i unplugged it, shutting it off, and after plugged it back in, turned right back on. So, I left it unplugged.

Anyone solved a problem like this before? and to what lengths did you have to go for a solution?

Can the spark plugs have anything to do with this?