finally got my truck back runs good they replaced the rear main seal with an OEM one becasue apparently the other one didn't seal properly .
when I got my truck back I drove into work and noticed coolant under my truck not allot but enough for me to notice I popped the hood and notice it is coming from the neck below the rad cap is there a fix for that or do I have to buy a new rad and for the life of me why are all the radiators plastic.

also I have this kind of Whining sound that I cannot place where it is coming from not sure it is the the belt ( was told that my water pump pulley is bent that story I wont get into) or possibly my alternator whining if it is the Alternator can I just replace the brushes.
In all my years of driving I don't ever remember hearing an alternator whine.

 

If alt is whining usually diode died. No brushes in an alternator. (generator yes)

If a pulley is bent means its putting a weird load on a bearing - could be bearing whining and about to crap out

and your 100% sure its not the radiator cap leaking?