Hose won't hurt at all, just don't do it if the engine is not running and is hot. If the engine is hot just start it an let it idle while feeding the hose water in. If it's cold just flush through, best way is to have the engine running while doing it though. When filling back up make sure to get the air bubbles out if big enough it can act just like a clog or thermostat an restrict flow causing you to overheat.
