Mazda Repair: 2001 MPV overheating after AC charged, coolant tank, ac condenser

Question
I recently had the oil changed and the AC recharged.  The next day the engine began to overheat, first when the AC was on then after running a few miles even with the AC off.  I checked the coolant and it was low - never had a problem before.  Suspect maybe before I realized the engine was overheating the coolant may have escaped through the overflow.  Replaced coolant and car still overheating.  Have to blast the heat to get home, but this is effective in decreasing the engine temp to the middle normal range.  Once when I had the heat running, it appeared that the AC turned itself on and the engine temp climbed immediately.  Do I have a thermostat problem,is my car simply possessed or what else could be wrong?   I see no leaks from the coolant tank, the hoses or the radiator.  The radiator fan runs properly.  Thanks. L.

Answer
Check the oil, the reason I say check the oil is that sometimes if the mechanic is using an oil filling pump that automatically dispenses the oil it can malfunction and only put in a fraction of the required quantity of oil. Thus causing more friction and higher engine temps.
Then check to see if the fan is working at both speeds. Anything with AC save trucks and older cars use ether 2 fans or a 2 speed fan for cooling the AC condenser when the AC is on. If the second speed or second fan is not working you will get this problem. Also, you can have the system pressure tested to rule out any problems with the systems integrity. Past that only a few things can cause this. One being a bad water pump; however, I am more favored to the thermostat as the heater would be ineffective if the water pump was going. You can also check the radiator cap to make sure the rubber sealing surface on the underside of the cap is not ripped or missing. A core obstruction cannot be ruled out but is unlikely in this vehicle. I suggest a new thermostat first along with a good flush and fill using Peak Global antifreeze a NAPA Superstat thermostat. Also, you may be able to extort some free work from the shop that did the work if you whine to them that the problem was encountered directly after they worked on it. If you find the oil to be low I defiantly suggest that you bring it back to them and have them check it over for possible damage. It seems rather strange that this problem crops up now after something as simple as an AC recharge and Oil change.


Regards,


John