This happened on one of my 240's. I had to remove the air intake grill and was able to make a very long extension for my WD-40 spray can by using small shrink tubing to join the small extensions together. I managed to get the extension down to the motor and gave it a good long squirt. It worked! No more noise.
Perhaps, hopefully, your 190 blower will be easier to access than that damn 240 was.

__________________
'76 240D-Sold
'78 240D-Sold
'85 300 SD, 165K-Sold
'88 300 TE, 165K-Sold
'64 Porsche 356C Cabriolet- under restoration
'86 560SL 124K Miles-Sold
'94 320E Wagon, 74K Miles-128K Miles JUNKED
'06 E350 Wagon, 84K Miles
07 SL550, 14K Miles