Coolant residue around expansion tank cap

[edwardh1]

Both my moms buick and my 04 highlander have a coolant expansion tank away from the radiator. the small hose from the radiator cap goes to the expansion tank. the expansion tank is vented.
on both cars I sometimes find dried coolant around the expansion tanks vented cap. Has anyone else seen this? never drips on the ground and the coolant level in the expansion tank when hot is way below the vented cap.
what causes this?

 

[beast3300]

Normal crunchies, I wouldn't worry about it. It is just dried coolant.

 

[bepperb]

The Highlanders of this vintage have a really poorly done hose from the radiator that tends to leak at both ends. I wouldn't worry about it. While the overflow isn't pressurized, there will be pressure in there (its an expansion tank, afterall) and likely that's condensation from the vapors pushed out to make room for the fluid.