comes & goes. Any fans behind the dash?

Check speedometer cable for lube where it enters speedo head.

thanks rocky, I'll check it out, Jack

Heater blower if the sound comes from the center, air sampler if its on the right, speedo or cable if its on the left

You didn't specify when the noise is happening.

On my 500SL, one of the vacuum pods for the HVAC system leaks. Sounds like someone letting air out of a balloon! A/C doesn't work anyway, so I have that vacuum line blocked off.

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