Got a call at work today. My wife said her car overheated on the highway on the way to shopping. Intermittently got a warning light for the engine temperature. She pulled over and waited til it went away (she forgot to check the gauge, though!). Proceeded and it happened again just before she parked. A/C was pushing hot air.
I responded and it had been sitting off for nearly an hour. There was absolutely no fluid leak. Too hot to remove pressure cap, but overflow was full at normal level. All hoses and the belt intact. All looked good. Oil good and clean, no contaminants, down only 1/2 quart after more than 2,000 miles. Top hose was hot, but I could grab it. Bottom hose was nearly room temp, same as my identical car, and it looks like the thermostat housing on the 2.4L engine is at the block end of the bottom hose.
Started and ran it for 20 minutes, it got up to normal temp (halfway mark) and stayed there. Ran the A/C and it came on cold. Temp then increased no more than an additional 1/16, maybe less. Drove around the lot, all was normal. Only fault code was a P0441, unrelated, that appears periodically. Warning light was off the whole time. Both fans were running as soon as I started it, and continued to run. I did not observe a high-speed mode, even with A/C on.
Drove her car home, with her following in my car. About a mile down the highway, with A/C off, it climbed to 3/4 scale. I was about to pull over and call AAA (still 20 miles from home), when I turned on the heat instead, full temp at 1/2 fan speed. The engine temperature came back to normal 1/2 scale, so I continued. The heat output on this 82F day was incredible, my feet were burning up, almost painful. But the engine stayed normal temp all the way home. I just about melted my sneakers from the heat.
For the last block, I turned the heat off, and the temp went up about 1/16th additional in just 15 seconds or so. I parked it.
Diagnostics:
No leaks. Hoses are fine. Fluid appears normal in appearance, level and color. So does oil. No milk. Normal power, sound, etc.
Driveline is fine, no dragging brakes, shifts fine.
No noises, belt is fine. I think the pump is OK, since the heat output was legendary. If it were not pumping, the interior heat would be based on diffusion alone of heat through the coolant to the heater core, and would not be scalding continuously for 1/2 hour ride.
Thermostat appeared to function OK, as when I first started it, temp was at 1/8 scale and it climbed for 5-10 minutes slowly to the normal halfway mark. No oscillation. And it was steady there with the heat blasting for 20 miles.
I suspect that the PWM controller for the fans is bad, and it is only running at low speed. I never heard or saw the fans go into high-speed mode. How do I test for this? Can I force this? Turning A/C on and off did not change them, both fans ran at the same speed, and were not loud as I would expect a high-speed mode to be. Any help on fan control diagnostics appreciated, as well as anything I overlooked. Thanks.
I responded and it had been sitting off for nearly an hour. There was absolutely no fluid leak. Too hot to remove pressure cap, but overflow was full at normal level. All hoses and the belt intact. All looked good. Oil good and clean, no contaminants, down only 1/2 quart after more than 2,000 miles. Top hose was hot, but I could grab it. Bottom hose was nearly room temp, same as my identical car, and it looks like the thermostat housing on the 2.4L engine is at the block end of the bottom hose.
Started and ran it for 20 minutes, it got up to normal temp (halfway mark) and stayed there. Ran the A/C and it came on cold. Temp then increased no more than an additional 1/16, maybe less. Drove around the lot, all was normal. Only fault code was a P0441, unrelated, that appears periodically. Warning light was off the whole time. Both fans were running as soon as I started it, and continued to run. I did not observe a high-speed mode, even with A/C on.
Drove her car home, with her following in my car. About a mile down the highway, with A/C off, it climbed to 3/4 scale. I was about to pull over and call AAA (still 20 miles from home), when I turned on the heat instead, full temp at 1/2 fan speed. The engine temperature came back to normal 1/2 scale, so I continued. The heat output on this 82F day was incredible, my feet were burning up, almost painful. But the engine stayed normal temp all the way home. I just about melted my sneakers from the heat.
For the last block, I turned the heat off, and the temp went up about 1/16th additional in just 15 seconds or so. I parked it.
Diagnostics:
No leaks. Hoses are fine. Fluid appears normal in appearance, level and color. So does oil. No milk. Normal power, sound, etc.
Driveline is fine, no dragging brakes, shifts fine.
No noises, belt is fine. I think the pump is OK, since the heat output was legendary. If it were not pumping, the interior heat would be based on diffusion alone of heat through the coolant to the heater core, and would not be scalding continuously for 1/2 hour ride.
Thermostat appeared to function OK, as when I first started it, temp was at 1/8 scale and it climbed for 5-10 minutes slowly to the normal halfway mark. No oscillation. And it was steady there with the heat blasting for 20 miles.
I suspect that the PWM controller for the fans is bad, and it is only running at low speed. I never heard or saw the fans go into high-speed mode. How do I test for this? Can I force this? Turning A/C on and off did not change them, both fans ran at the same speed, and were not loud as I would expect a high-speed mode to be. Any help on fan control diagnostics appreciated, as well as anything I overlooked. Thanks.
