I am a relatively new, but not the first owner of a 2014 Caterham 7 360 SV. Wet sump. 2.3k miles.
At warm idle after spirited driving (commuting is hit or miss) the car develops a rather loud and annoying squeal / whine. Initially I suspected the usual suspects - belt and , pulleys , or water pump. So I changed the belt, noise remained. Sprayed the pulleys a little, no noise change. So after reproducing it I removed the belt and was still able to get it to make the noise...albeit a bit less shrill / deafening.
So far I can make the noise go away by pinching the vent pipe from the top of the camshaft cover - interrupting the vacuum - or if I remove the oil filler cap.... but not knowing the architecture of the duratect I'm pretty much flying blind. Could it be the one way check valve in that line leaking? Any other sources of a shrill sound on the driver side of the engine that are common? Water pump seems unlikely but I don't know how that might be impacted by the vent I'm pinching - could be it's inadvertently affecting idle in a way to make it disappear... But that correlation seems weak since its present without the belt installed...