ok so i have the D15a3 engine and i just put a new thermostat in and a new o2 sensor and my car still seems to get really hot when i drive it, it'll over heat driving to auburn from maple valley. i thought maybe the water pump or the heater core, but idk really what to look at first.

 

Maybe air bubbles in the cooling system. Run the car and blast the heater, check the radiator hoses to see if you coolant in circulating. See if your radiator come on.....check this page out....good luck.
http://www.redpepperracing.com/forum...e=%2Bover+heat

 

Make sure you follow the proper coolant bleed procedure. When you're filling the coolant, you need to have the temp selector inside the car set all the way hot. And you also need to have the air bleed screw open and fill the coolant until it quits bubblling out the top of the screw. Also, overheating could be due to a water pump, or possibly clogged radiator. Try flushing it out. If your heater core is bad, it will probably be leaking more than anything, I don't think a clogged core would cause the car to overheat, since the way the coolant lines are routed, it should bypass the core.

Worst case is that you have a blown headgasket. Does your car blow any white smoke? Or does your oil look milky or brown?

I'd guess water pump, if I had to throw something up in the air. It would be a good time to do the timing belt too probably.