I have an 01 D, 4.7, with about 160K miles. It's not my daily driver any more, so I only drive it sporadically these days.
It's always run on the cool side of normal, and I rarely see any variation in that. Recently I was stuck in a traffic jam where we spent minutes at a time not moving. Outside temperature was probably in the 70s (this was central valley California--sorry east coasters), and I noticed the temperature creeping up. It got just below the danger zone (the second highest mark on the gauge), and I was getting ready to pull over, but then it slowly started to come back down. It did this once or twice more before I could pull off at a gas station. There was water in the overflow tank, which was my biggest fear. The mechanical fan was spinning slowly, although at that point the temperature was pretty much back to normal, so I don't know what that means.
During this process, I didn't hear the fan kick in, but I can't remember ever hearing it turn, other than every time I do a cold start.
I checked the water just before leaving on the trip, and I had to add some to the overflow tank, but it was full at the radiator cap. When I got home I checked again, and it was still full, with water in the overflow.
I can't remember the last time I was stuck in this kind of traffic in the D, so I don't know if I have a problem or not. I haven't had a chance yet to run her up to temperature to see if the fans are spinning.
Does this sound like normal behavior, or should I start thinking about replacing the fan clutch, or temp sensor, or maybe the radiator? I guess it could conceivably be the thermostat too, but I've never had a thermostat fail other than by just sticking closed. I put a VOM on the temp sensor, and it read 16K ohms at about 60 degrees outside temp, which seems to be within spec, although maybe on the high end. But I suspect it's not that sensitive a sensor, given that the FSM shows a pretty wide range of resistances. When it's cool, the mechanical fan will turn by hand, but it's not what I would call "freely," which is what the FSM calls for. Other than that, I'm not sure what kind of tests I can run for something like a bad fan clutch or clogged radiator, and it looks like pulling the thermostat is a bit of a PITA.
It's always run on the cool side of normal, and I rarely see any variation in that. Recently I was stuck in a traffic jam where we spent minutes at a time not moving. Outside temperature was probably in the 70s (this was central valley California--sorry east coasters), and I noticed the temperature creeping up. It got just below the danger zone (the second highest mark on the gauge), and I was getting ready to pull over, but then it slowly started to come back down. It did this once or twice more before I could pull off at a gas station. There was water in the overflow tank, which was my biggest fear. The mechanical fan was spinning slowly, although at that point the temperature was pretty much back to normal, so I don't know what that means.
During this process, I didn't hear the fan kick in, but I can't remember ever hearing it turn, other than every time I do a cold start.
I checked the water just before leaving on the trip, and I had to add some to the overflow tank, but it was full at the radiator cap. When I got home I checked again, and it was still full, with water in the overflow.
I can't remember the last time I was stuck in this kind of traffic in the D, so I don't know if I have a problem or not. I haven't had a chance yet to run her up to temperature to see if the fans are spinning.
Does this sound like normal behavior, or should I start thinking about replacing the fan clutch, or temp sensor, or maybe the radiator? I guess it could conceivably be the thermostat too, but I've never had a thermostat fail other than by just sticking closed. I put a VOM on the temp sensor, and it read 16K ohms at about 60 degrees outside temp, which seems to be within spec, although maybe on the high end. But I suspect it's not that sensitive a sensor, given that the FSM shows a pretty wide range of resistances. When it's cool, the mechanical fan will turn by hand, but it's not what I would call "freely," which is what the FSM calls for. Other than that, I'm not sure what kind of tests I can run for something like a bad fan clutch or clogged radiator, and it looks like pulling the thermostat is a bit of a PITA.
