Radiator on 1993 BMW 325i

i just replaced my thermostatic and radiator and my car started over heating again after about a month or so after I filled my raidator cause it was low

2 answers
early BMW's had a plastic water pump impeller. it may be
worth it just to pull the water pump to make sure that your pump has the metal impeller.
It's possible you may have had an air pocket in your cooling system. Hopefully, the overheating is an isolated incident. Fill the coolant and run the vehicle - see if the problem reoccurs.