overheats on 1991 Chevrolet Cavalier

have new radiator, hoses ok, new thermostat but car overheats. If I run the heater it cools it down a lot

Asked by for the 1991 Chevrolet Cavalier
5 answers
check the type of coolant u have they recommend dexcool for all gm vechicles and its the orange color not the green color coolant plus check the fan operation and if thts not it burp the system or flush the system it could be clogged
possible air pocket in cooling system. try bleeding it
Check the radiator fan operation, sounds like it's not doing it's job.
check water pump-do you lose radiator flluid
same problem..new fuel pump wire harness or fuel pump..make sure you have the fuse for the heater first