something that may or may not work.this is a good way to find noises in those hard to get to areas.
get a small tape recorder with a mike that has a long cable. tape the mike to differant places to isolate the area.
maybe some other way to listen while you drive. cell phone mike with extended cable while you listen on the head phone portion. just dreamed this up but there are plenty of listening devices out now.
maybe some one else can come up with some thing easy.
good luck
rich

__________________
88 300E White, sold 9-04
88 190E Black 2.3 sold
90 300CE White, Grey sold 12-24-04
92 400E White,Grey Sold 5-06
90 300CE 91K Signal Red,Black Sold 2007
1989 300CE Smoke silver,Tan Sold 1-08
1993 300E 3.2 M104 motor
1991 300CE White,Grey
1994 E420 beautiful car,gone to new home
1994 E320 Smoke an Parchment.Beautiful car