Hi! Does anyone know why there is a loud fan noise under the hood when the engine started warm/hot (which mean after driving for 10-30 min, stop by someplace for a while then trying to start the engine). The engine is on but there is a loud fan noise under the hood for 15-30 seconds briefly then disappear. It happen occasionally but there is no warning light on the dash board appear. Does that mean something gonna happen in the near future? I had an SLK 1999.
Thanks

 

Have you had a look??
If these engines had a viscous fan it would be that spinning out at 1st start but they dont..

Most probably it is a belt idler bearing that is dry and as it warms up a little bit of lube runs around reducing noise.
Open hood, have a listen. A dowel makes a good stethoscope.
Also slk230s in some markeets use the Supercharger as an air pump to reduce pollutants duing warm up so it comes in for a while at all revs.

Bazzle