2006 Ford Ranger 4.0 SOHC V6, 62k miles.
I have an intermittent problem where the coolant temp gauge gets into the hot zone for a few seconds and goes down. It'll go like this: Start truck up after it's been sitting overnight. Coolant gauge slowly rises as engine warms up like normal. Gauge gets to normal (middle of gauge) and keeps going, and going, till it maxes out. It stays there for a few seconds, and then instantly drops right back to the normal zone, right in the middle of the gauge. It stays normal the whole rest of the trip. It only happens as the engine is warming up. I'm a little doubtful that the engine is actually overheating, and I think there's probably just something wrong with the gauge or sender. It's very intermittent and has only happened about 6 times in the past 2 months or so. And only twice it maxed out the gauge; the other times, it started creeping past the halfway mark and went back down. Nothing seems to be wrong with the engine. No coolant loss, coolant is relatively fresh.
Could it be a thermostat intermittently sticking closed, and finally opening up after the engine gets too hot? Or do you think it's a bad sender? I really hate intermittent problems; they're such a pain to diagnose.
I have an intermittent problem where the coolant temp gauge gets into the hot zone for a few seconds and goes down. It'll go like this: Start truck up after it's been sitting overnight. Coolant gauge slowly rises as engine warms up like normal. Gauge gets to normal (middle of gauge) and keeps going, and going, till it maxes out. It stays there for a few seconds, and then instantly drops right back to the normal zone, right in the middle of the gauge. It stays normal the whole rest of the trip. It only happens as the engine is warming up. I'm a little doubtful that the engine is actually overheating, and I think there's probably just something wrong with the gauge or sender. It's very intermittent and has only happened about 6 times in the past 2 months or so. And only twice it maxed out the gauge; the other times, it started creeping past the halfway mark and went back down. Nothing seems to be wrong with the engine. No coolant loss, coolant is relatively fresh.
Could it be a thermostat intermittently sticking closed, and finally opening up after the engine gets too hot? Or do you think it's a bad sender? I really hate intermittent problems; they're such a pain to diagnose.