I been having the same issue on my 2009 LR@ with 70k miles on the clock. I recently replaced the alternator and that was about $800 so I am not happy about this. I did a search on the whistling noise and the range rover owners related it to a bad ECU fan. I tried looking for this fan on the LR2 but no luck and I am not going to start dissecting the car until I know for sure what is wrong and where the faulty part is located. I took the car to the mechanic who replaced the alternator and he said something about the power steering pump might be on its way out. He then said he used some sonar instrument that locates noise and that is where its coming from. I wondered about that, but anyway I am glad I found this thread and I will start the car now and heat it up to provoke the noise, remove the dipstick and see if it goes away. If so I will order the parts and change them myself since they sit atop of the engine. It looks like a fairly easy task. I just heard the noise and sure enough it went away when I removed the dipstick. Going to order the part now and swap it myself. Do I have to use any gasket sealer on the gasket? Thanks in advance!