1983 W123 200T: there is a odd noise coming from the engine bay when the car is at rest, don't laugh but it sounds like the distant sea! obviously it isn't the sea because there's no fish or even any water in my engine, but perhaps a small fan or pump of some sort. However, as soon as i depress the accelerator it stops until i release it.

the noise is not intermittant, it seems to be directly related to the gas pedal.

is this normal? or is there a more heinous cause that i should be attending to?

thanks in advance for you help.