Things that whirr in the engine bay (apart from the obvious):
* Damaged blades on radiator fan. Look at the root of the blade for cracking. This is extremely dangerous as it could cause the blade(s) to start nicking away at the radiator.
* Thermal fan cutting in. There's a small electric fan down at the bottom right hand side of the radiator (the car's right hand side). It usually only cuts in when the coolant temp is at 105C or the aircon compressor is on.
* Turbo flutter. Generally it shouldn't. Have someone take a poke at your impeller. If the shaft wobbles more than a tiny amount, your turbo might be ready to pack it in. Please don't talk to me about turbo woes, my car is now on its third.
* EGR leak. Usually they break around the base of the gold pipe where it joins the exhaust manifold but it could be a gasket around the other side on the back of the EGR valve. If memory serves, the 2011 D40s had a flow sensor, so blanking the EGR completely will probably trigger a Check Engine Light.
* Idler pulley. It's located towards the right hand side and below the alternator. There's a cap over the front so you can't spritz the bearing directly but it would pay to give it a squirt under the cap with the fine tube on a can of silicone lube.
* Alternator pulley. Again, happened to me (must be lucky). The pulley broke off the shaft and the only thing holding mine in place was the tension of the serpentine belt. Alternator was replaced, problem solved. I don't think the 2011 had a "smart" alternator, it should be similar to mine.
* Exhaust manifold < - > turbocharger interface. Mine came loose (told you, I'm lucky) and was just loose enough to make the gasket sound like a reed instrument (you know, saxophone/clarinet etc but without ANY of the skill needed to do a decent job). Sometimes it would flutter, other times it would shriek.
Hope that helps.