You may check the water pump. Very simple test, have the car running grap the radiator hose while holding the hose rev the engine you should feel a pulse in the hose each time you rev it. Make sure your car is up to temp. first. If that is good. You may want to replace your thermostate, Very cheap to do. It may be stuck shut or open. Your heater may be caused by your thermostate to, if not the heater core may be pluged. A good system flush may be a good Idea to. Check the front of the radiator to for bent fins or trash. There can be many possibiltys here but always check the simple stuff first.
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