Hissing sound on right side of dash w126

[BO'H]

Hi all,
My recently recommissioned w126 560SEC, which had been off the road for 7 years has, after 200 miles, got a strange hissing sound coming from the right hand side area near the dash speaker when i am cruising along that disappears reduces greatly under acceleration. I have searched online but cannot see an answer plus i have looked under the bonnet. Has anyone come across this before?
Thanks,
Benedict.

 

[robparker]

Have the vacuum lines come off the headlight leveling switch maybe?

 

[grahamcol]

As above and i had similar with my 202 although in my case the headlight levelling contraption had failed.

 

[JohnArnoldBrown]

Have any of your neighbours lost a snake recently?

 

[BO'H]

Have the vacuum lines come off the headlight leveling switch maybe?

Hello - many thanks. I’ll take a look. If the radio worked I’d blame a dodgy speaker!

 

[brianbrian]

Check every thing on the vaccumm side works, should only take a few minutes.

 

[BO'H]

Thank you to all.