I've got a 2001 Durango, 4.7L with an overheating issue. I'm pretty sure the radiator is shot but in the process of diagnosing the problem I noticed that the electric fan would only kick on at a fairly high temperature and would kick off when vehicle is left at idle.

Perhaps this is part of the overheating issue also. The fan obviously works but perhaps whatever tells it when to engage is faulty.

The question: When should this fan engage? At what temperature? Only while driving or is it totally dependent on temp?

A little more info if it matters. New water pump, new thermostat, new coolant, system bled properly as per instructions from Hydrashocker. Soon it'll have a new radiator. I live in the hottest place in the US so the cooling system is that much more important/taxed. Thanks for your time.

 

Could you post a pic of where the temp needle is when it comes on? Does the e-fan come on with the a/c? It helps cool off the rad and a/c coil. It always comes on with the a/c unit running. Is the clutch fan running? The e-fan should come on between 180 and 210 degrees( if I'm wrong, please correct me). If the fan relay is shot, then it wouldn't turn on at all. Maybe someone else would know what controls it. PCM? HTH.

 

the efan goes on whenever the a/c is running, and whenever the temp gets over 210, it has nothing to do with ground speed or anything else strictly temperature, there should be a temp sensor which triggers it, but if thats broken (i think its the same one as for the temp gauge in the cab) the temp gauge would not read accurately

 

OK. Based on what you both said, I suspect it is working fine. The reason I was concerned is I was working on the truck and observed something I thought strange.

It was at "normal" operating temperature and idling. By normal I mean just a little past the first notch, 80 degrees ambient air temperature, engine idling for about 15 minutes. The clutch fan was on but the electric fan wasn't. When I revved the engine the electric fan immediately engaged and then disengaged as soon as I let it idle again. Common sense would tell me that it was solely dependent on the temp, but the fact that it came on and off when revved or not made me start thinking. Likely, revving the engine caused it to hit the temperature threshold needed to start the fan.

I haven't tried it with the A/C, but will tomorrow. If I understand correctly, the electric fan should be on whenever the A/C is running, regardless of engine temp. Is that correct? If so, then if it's on with the A/C I will consider it working and not worry about. Like I said earlier, I'm about 955 sure the radiator is the culprit for the overheating. Thanks guys.

 

Yep, the e-fan turns on with the a/c. Good luck with the rad swap!

 

From your tone it sounds like the radiator swap may be a beast. From what I can see it looks simple enough. Do I hear the voice of experience talking? Am I missing something or are you just leaving room for the normal Murphy's Law type problems. I'm no stranger to that. Either way, it's gotta get done. It should be here on Monday. I'll definitely let you know how it goes.

 

No, no... LOL. I just meant good luck! I have no idea how much work it is to to swap out a rad. The experts will have to chime in to tell you what the swap entails. Keep up what you're doing and do a write up on the swap. I'm sure you'll help someone else down the road with it. I hear the chilton's and hayne's manuals are good referencs guides.

 

You nailed it on the head!

Maybe when you hit the throttle a rush of hot water ran over the sensor and engaged the fan. Still, I would replace the sending unit because it sounds like it's late and isn't functioning correctly. The sending unit tells the PCM whats the temperature then the PCM tells the electric fan to turn on. If the sensor isn't reading correctly and the truck is up to temp enough to engage the clutch fan then I think the sending unit is not reading correctly.

I think you radiator is fine.

If you would like a service manual I can fernish one. Radiator isn't that hard but purging the system can be after installation.

 

Hydrashocker, one quick question. Is the temp sending unit for the PCM the same one as for the temperature gauge? If so I would think that the sending unit is fine since the gauge seems to be working fine. Am I off track on that? Could the problem with the efan be caused by something other than the sending unit?

 

The Engine Coolant Temperature Sensor sends its data to the PCM. There is no other sensor in the loop other than an input from the A/C (when engaged) and that will turn on and off the fan as well.

Now the E-fan is geared to come on at 217 degree's F and turn off at 208 degree's. So the coolant needs to drop that 9 degrees F to turn off the fan. With you telling us that it kicks on and off THAT quick with only a touch of the throttle (to me) means that the sensor is starting to fail. You usually would notice this fluctuation but at only 9 degree's you might not be.

For like only $10 bucks, just replace it.....IMHO