Originally Posted by srmmmm

Wipe them off thoroughly with denatured alcohol, then seal the cracks with a continuous bead of aquarium or marine grade silicone sealant (3M Part Number 08019). Allow 24 hours for curing, then use spray silicone on the rest of the boot for protection and surface lubrication.

2002 X5 3.0 314,300 miles
2014 428i 24,100 miles

2004 325i sold at 123,600 miles
2001 325i sold at 66,000 miles

1970 Firebird - Under restoration