I filed the fan down to snugly fit the housing. Then I had to file the CEM-housing because applying some force led to the fins of the fan sometimes touching the CEM-housing ever so slightly causing noise. The fan is operated through a 100ohm resistor (slower RPM but/and lower noise) via the cigarettelighter (on with contact).
Part of the CEM slides out and then you can open it up. You can see the tin casing shielding the processor from interference but also making sure it has little to no airflow around it. I fitted a heatsink which comes with heatconducting double sides tape, hammered out the metal lid to accomodate the heatsink and the lid that covers the PCB now presses down so the heatsink is pushed onto the processor with a little force. So now I probably end up with problems due to the PCB being under stress
The fan sits over the tin box, so it sucks air past it. I think either solution might have been enough, but applying both should double my chances of success.