3942's cooling fan is running at maximum revs (and noise) as soon as any engine speed is commanded.
At idle the fan speed (and noise) falls significantly.
Of course this might be to counteract overheating, though it will have an adverse effect on fuel economy.
There is something unusual about this situation (not all similar vehicles are as noisy).
It could be a damaged fan.
RE: Go North East: Latest News & Discussion - June 2015