I had one of those leaks once. After checking all the obvious culprits and fixing a bad water pump, I found out it was the thermostat housing gasket. Very hard to check... but might be worth a look.

 

Thats what it was the thermostat gasket. When the truck got hot and the thermostat was about to open it was pushing alittle bit of water out. The thermostat looked so so very bad. I look at it with my mouth open and a wtf look one my face. Some dumb a put stop leak in it befor i got the truck and it all but had the thermostat covered and stoped up i have to fush it about 6 times to get all the crap out but its all good now. About 4 1/2 hour to do it but a job well done LOL. TY for all of the help!!!!!!!!1