That third outlet wasn't threaded on the pump I received, just a plain pipe spigot. I blanked it off with a short bit of hose with a bolt plugging the end, obviously with hose clamps. A bit of a bodge. However there's a guy at work who's into rallying, and apparently in competition vehicles they're always blanking off unused bits and pieces. He pointed me to things like these, and one day I'll get around to neatening it up ...
Application: Blanking plugs & Hose finishers Hose Construction: Moulded Without Reinforcement Temperature Rated: -60°C to +180°C Material: VMQ Silicone Rubber Download Data Sheet
www.autosiliconehoses.com
