I may have jumped the gun on the head gasket issue. I read the tag as a cooling problem so I re read your problem. Is the truck overheating ? Where is it leaking ? there is a 1 " short rubber hose that is under the intake manifold that is really tough to get to and to see. This is a common hose leak for older trucks due to not being able to get to the location..........replacement is awkward but do-able with a little bit of coaxing.........