So how do you keep your engine bay clean in dirty conditions?
I have found with Andy (bay kombi) that way to much dirt enters the engine bay on very dusty roads. One particular trip left the engine bay completely caked in dirt, can't be too good for cooling.
The beetle has no such problems!

Maybe just driving slower to keep the dust down?
:thumb

I generally stuff a heavy duty shade cloth material around the air vents. This keeps most of the dust out and engine COOL

It would probably be a good idea to clean the shade cloth kinda regularly too as to not restrict too much airflow...

dust on the OUTSIDE of the engine is OK:
a sign that vw engineers did it right (hey. it got you there...). service the aircleaner often. When the engine is cold, start it and spray H2O into the fan witha hose. If necessary, run a coke bottle full of water miscible degreaser thru first. You will have a nice clean engine under the shroud. If no oil leaks in your engine(?), delete the degreaser...
btw...that is a nice bus you have

I actually saw one the other day which had the sides modified and big ass k&N filters on there. It was at the servo and belonged to a guy called Dave from WA. He said it worked great and kept all the dust out of his engine bay and reduced the wear on the engine.

Maybe that is an option ....

Hmmm... plenty to think about.
The K&N's would have to be huge to prevent pressure drop through them.

As I an fitting side scoops, it may be an option to put a coarse screen there?

Dust in the engine bay can be just as bad under the cooling tin as it is outside!