Thank you, Jeffsr. I went out and tried that. I didn't get smacked in the face with any foam, but the whistle got a lot quieter, at least for now. Maybe I can borrow a fiberoptic Endoscope and go foam fishing!
2003 Firemist Red/grey leather SL 500
2015 Palladium Silver/black mbtex GLK 350
1987 Smoke Silver/burgundy mbtex 300E Sportline (SOLD)
Click to see 87 300E