Let me say first that truck runs and tows great! Checking under hood the other day I noticed that top rad. hose was sucked in. This was with cold engine in the morning. When warmed up all looks fine. Expantion tank is proper level and the fluid looks new, I was wondering if there is some sort of blockage between tank and rad. Seems like it can't pull fluid back as it cools down. Whatcha think? Oh this is a 04 LB7. Thanks for any help.