I have a 2005 ranger with the 3.0L engine and Ive had a coolant leak for a few weeks now and i finally stumbled on what i think is the cause. This is a picture of what looks like a set screw hole that's missing the screw. this is right behind the fan pulley. My question is what is the screw size for this hole? My initial thought was to go to harbor freight and buy the set screw pack that has a bunch of different sizes but i don't want to waste my money if it ends up being metric or an odd size.

 

That is the "Weep Hole" it's there to let you know the seals in the water pump have failed and that you need to replace your water pump.

 

Thanks! I did a little research on that after coming to the same conclusion earlier. It seems that the water pump replacement is kind of a pain in the ***. Would plugging that hole prove as a temporary fix for a few weeks until I can get the time to change it?