strange noise

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.

[Robby Ackerman]

It could be something as innocuous as the various drive belts or a pulley tensioner making the noise. For the past five years our 123 300 D has made a noise like you describe at idle.

thanks for your reply.

linking the noise to the transmission certainly would make sense.

i noticed today that it makes the noise whether the car is at standstill or in motion. this might limit the possibilities of what could be causing it.

it's the weirdest thing but i've found the culprit.

there's a little roller switch on my control consol with a light symbol on it. i'm not sure what this is for, i am guessing dashboard illumination, but since i currently have no illumination in my dashboard i can't tell.

anyway, for some strange reason, if this switch is not rolled into the top position the car makes a strange hissing noise!

if anyone can tell me what this is all about i would be very interested to know. at least in the meantime i have a bit more peace and quiet.

thanks jb

[Robby Ackerman]

It could be the adjustment for the headlight height angle. It is vacuum operated. It may be that a hose or two have become disconnected. Rotating the wheel should raise and lower the headlights.

Typically the dash light rheostat is a knob on the instrument cluster. You can remove the instrument cluster and do a little R&R on the rheostat (clean the contacts) and make it work or replace it. They are about $25.

Robby

thanks for that info, to tell you the truth, i thought it looked more like a headlamp angle controller, but my friend who was brought up in mercedes assured me it wasn't! and i believed him.

yes, your thoughts make much more sense. as for the instrument light, it's disappeared......i'll try and find it tomorrow.

thanks.