Bleeder Fill Cap Install tips
Just a reminder for anyone that may not have had this part off their engine yet - the bleed bolt can be very tight, mainly from corrosion over the years. In order to avoid twisting/damaging the brass standoff it screws into, there is a 3/4" hex shoulder on it at the top, right under the cap. I use an open end 3/4" wrench to hold it from twisting and a 1/2" wrench or socket on the bolt. Note that used caps are brittle and can't take much handling.
The bolt's threads are approximately 1" long. When the bolt is removed, confirm that the bleed hole is clear - clean/probe it open if not. The hole is in the center of the end where it travels up the bolt to a horizontal hole that exists on either side, approximately 3/16" inch below the shoulder that holds the cap. I always fill the bleed tube whenever I R & R just the bleed screw.
And as always, work on a cool engine any time you open the cooling system.