I bought a 2004 Sentra that was rebuilt w/ 45k miles. I had to replace the radiator and ran the car for another 55k, During the summer I had to replace the mass airflow module (twice). The car runs now but hotter on the guage than before at highway speeds and the air conditioner blows warm when this happens. A mechanic replaced the thermostat and checked the 2 fans on the radiator. No check engine light. This is my beater work car but I go 100 miles each way and I don't trust it now. Any suggestions?
Does the engine actually overheat or just run hotter than normal? The engine overheating won't have anything to do with the A/C blowing warm air, but the A/C running will ALWAYS make the engine run slightly hotter than normal. This happens because when you turn the A/C on, it places a load on the engine than produces more heat the cooling system has to deal with.
Also, have you inspected the drive belt? If it's worn, when you turn on the A/C it stretches slightly. If it's too worn, it'll slip and the water pump won't turn as fast as it should. And a excessively worn A/C compressor is harder for the engine to turn than a good one.
When the radiator was changed, was the system flushed? Also, inspect the lower radiator hose for softness, as sometimes the hose will collapse and block the flow of coolant.
February, 1, 2011 AT 1:10 PM
If the higher than normal operating temperature occurs only on highway driving, get the radiator checked, it could be partially clogged.