To; Chris Cross.
I have an 02 400 ISL which has the surge tank posted above that has a radiator cap and a 1/2 inch site glass to see coolant level. I have not had any cooling system problems and dealer, Cummins, checks mix and level at visits. 400 ISL engine is great, good mileage, almost 9, great pep, and it doesn't know theres a 3000 pound toad behind it.
Hope this info helps----- Thanks-- AJBJRVERS