water pump block off

In the summer I disconnect and block off the heater so it's a little cooler in the car. Tried 2 of those rubber caps (bought at NAPA) and both ended up leaking. After the 2nd leaked I measured the i.d. of the nipple and it was perfect to tap for a 7/16" fine thread bolt. I used a copper sealing washer under the bolt head and it worked great. Easy to remove when the colder weather hits and I want to hook the heater back up. As for the rubber caps, I used 1 to cover the bolt head for a clean look so they do have a little use. If you look close you can see it in this picture