capping off heater hoses

I've tapped several pumps to accept a 1/4" pipe plug but you gotta go slow and easy. Tap too fast and the aluminum will ball up and split the nipple. You also need to do it with the pump removed of shavings will drop down in it. After I install the pipe plug (use some pipe sealer on it) I slip one of the rubber plugs over it to clean it up. That's all those plugs are good for. Too thin to last under pressure.