This is sort of a multi-part post.

I just got back from a trip to Moab this past weekend. I live in Denver. My (new to me) 03 Dakota has the 4.7l V8 with the heavy-duty service/tow package on it. Pretty beefy truck from what I've gathered from other posts to this forum.

This truck was an upgrade for me after my '98 five-speed Toyota Tacoma was totalled in an accident in February. I can't help but notice that even with a V8, I can't get the truck much past 55 MPH on the steeper approaches to both the Eisenhower Tunnel and Vail Pass' without kicking it into second gear and push the RPM up to about 4K... which just creates this monster sound. There's no red-line on the tach, so I guess I'm safe?? Am I pushing too hard? I'm really curious because my Durango (5.9L V8) just cruises up and over those passes like they were ant hills.

Also, this weekend, I had the truck loaded up with bikes and camping gear coming back from Moab and just as I hit the top of the west tunnel at the continental divide (a little over 11,000'), the power band dropped like hell when the fan kicked on. I didn't see any reason for the fan to kick on. The temperature gauge was still hovering in the normal range (just above the "normal" indicator on the left side of the gauge).

Does anyone have any input? Thoughts? Suggestions?

 

from the experiences that i have with my dakota 2.5l 4 cyl., I had alot of trouble with the check engine light coming on and stuff, but anyways when the check engine light comes on your ecu goes into presset mode. even if the check engine light is not on it will still have that code in its memory.you can do one of two things to see if this is what is happening. you can take it down to see if it has a code on the computer or you can disconnect the battery for 2 minutes to wipe the memory of you computer clean. then start it up. if the check engine light comes on the you know there is something wrong with a sensor. but if does not come on and it runs better then before then you there could have been something wrong and somebody fixed it before you bought it and never turned the code off,or it could take awhile for it to come on. i know with the code on in my truck it has a hard time gaining speed on flat ground.and hell on hills. i was in new mexico this weekend and was doing 70 over steep inclines. i know you truck should do better then that cause its a v8. one other thing i was working on my gf's car there was a bad sensor on it and i had to disconnect the battery and let the memory of the computer erase and then start it back up to find the sensor that was bad. pretty strange but it worked out that way.

 

Soooo... your saying that maybe I should disconnect the battery to wipe the computer and give 'er a fresh start?

Anyone have any second opinions on this?

 

The clutch fan engages in response to air temperatures coming through the radiator. The temperature gauge on the truck is usually dumbed down pretty good -- because owners don't like to see variable temperatures on the gauges (something must be wrong!). So your coolant temperature was likely hotter than the gauge really indicated, and if you were going slow enough, the airflow through the radiator may have been hotter than normal, and the air temperature that the clutch saw was apparently hot enough to engage it (it works with silicone fluid). It sounds like the system was working exactly as designed.

Regarding the power difference between your 4.7L Dakota and 5.9L Durango, there's quite a bit of it (power difference). The 4.7L makes 235 hp and 290 lb*ftof torque. The 5.9L makes 245 hp and 345 lb*ft of torque. And the 5.9L's power and torque peaks are likely lower (in the RPM band) than the 4.7L's, which is good for towing/hauling.

 

So, I'm just trying to understand my truck here...

When that fan kicks on, it really sucks the horsepower, yes? Why?

If/when that happens again, what's my best course of action? Just keep motorin'?

If/when I have the truck loaded down, should I just take 'er easy and cruise up the hill at a nominal speed that doesn't over-tax the engine and how does all that relate to what I see on the tach and the sound the engine is making?

I'm curious about your statement regarding airflow and temp. When I hit the top of the tunnel, I was doing approx 45 MPH and the outside temp was about 41 degrees. That seems like it should be plenty of airflow along with cool temps to keep things cooled off, but I'm learning here.

Finally, what about towing/hauling in desert environments and higher temps?! The truck wasn't overloaded but if I've got a fan kicking on at 11,000' with temps in the 40's, I'm really curious what I'll encounter during some trips out west to visit my folks when I'm driving through Arizona and California with temps in the 90's/100's and I'm hauling or towing.

Thanks again for all the information. I consider it invaluable to help me understand my truck and how best to operate it.

 

Just curious if anyone might have any responses to my last post prior to this?

 

i was just on that pass on tuesday to go snowboarding and have much the same truck as you, only with the 5 speed. my fan didn't kick in but when it does since it runs off of a pulley it will sap a little bit of power, only about 5 hp. are you sure taht it was your clutch fan? or was it the electric fan? (electric fan comes on when you are running the a/c and isn't as loud as the clutch fan). those hills are a b*tch and a couple of times i had to drop it down to third (about 4000 rpms at 65-70) but i did have a bunch of friends and weight in it. in regards to your question about running at 4k rpms, its not bad, the truck redlines in the 5500 region and makes peak power at 4800 so its not going to blow up or anything. what other questions did you have?