The warm hose is the SUPPLY hose. The cold hose is the RETURN hose. Simply remove the return hose from the engine, duct tape a garden hose on it real good. Then remove the supply hose from the engine and hang it over the fender. Turn the garden hose on full blast. Liquid plumbr works good too. Sometimes you run into really stubborn clogs. Just dump some Liquid Plumbr into the upper most hose and let it sit a little while and then flush as outlined above. Works good. The Ford Taurus and Mercury Sable cars were really bad about doin that when I worked for Ford. That's how we used to clean um out. Saved our customers big bucks because the whole dash has to come outta those cars for a heater core replacement.