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Gen 2 Dakota fan
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113 Posts
Discussion Starter · #1 ·
I have a 99 Durango with a 5.2 with 142,000 miles that has an odd heat issue. The gauge never goes much past 140, even on warm days. Last week, i replaced the thermostat, and it got a little better, but, the only time it really has heat, which isnt much, is during city driving. Once i get on the highway, it slowly gets cold, and then stays that way, unless i pull off the highway and let it sit at idle for at least 15 minutes. It has done this since i have owned it, which is why i finally tried changing the thermostat with an OEM one to see if that would fix it, and nothing really changed. Anyone have any ideas on what it might be?
 

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C'mon Dodge - NEW DAKOTA
2003 Dakota Club Cab Sport 4.7L
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670 Posts
A recent thread discussed a very similar problem. See this thread:
 

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Gen 2 Dakota fan
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113 Posts
Discussion Starter · #3 ·
After a 34 mile round trip, i checked the upper hose, and both heater hoses with a temp reader, and they all read between 156 on both heater hoses, and 161 at the upper radiator hose, so i doubt a flush will fix that issue, and, since it get heat at lower speeds and idle, im pretty sure its not the water pump. Fan clutch maybe?
 

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Gen 2 Dakota fan
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113 Posts
Discussion Starter · #4 ·
A recent thread discussed a very similar problem. See this thread:
I read that post before i made mine, and, if you read it, either he has a few typo's, or something else is going on, because, he said he went from a 180 degree, to a 160 degree, then reversed the heater hoses, and then the gauge now reads 210 and he has heat. My question is, how, with a 160 degree thermostat.
 

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2003 RT (5.9)
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449 Posts
. . . that has an electric fan, right? Maybe try removing your pulley driven fan & clutch & see if it runs any warmer with just the electric fan. I know that people are saying they are doing that just to improve their mileage & grab a few more HP, but if it does run warmer for you, that probably would point to the clutch.
 

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Gen 2 Dakota fan
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113 Posts
Discussion Starter · #7 ·
. . . that has an electric fan, right? Maybe try removing your pulley driven fan & clutch & see if it runs any warmer with just the electric fan. I know that people are saying they are doing that just to improve their mileage & grab a few more HP, but if it does run warmer for you, that probably would point to the clutch.
No, mine doesnt have the electric fan, just the engine driven one.
 

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C'mon Dodge - NEW DAKOTA
2003 Dakota Club Cab Sport 4.7L
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670 Posts
the clutches typically do fail "on", sort of a fail-safe. Here's the test. When you first fire up the truck and drive off, the fan should sound like a jet engine until the clutch warms up and releases. Then it will sound more "normal". It's very common for these things to fail. You could pull the blade off and drive a limited distance and see how the truck reacts. On a cold-ish day you should be fine.
 

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Gen 2 Dakota fan
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113 Posts
Discussion Starter · #9 ·
the clutches typically do fail "on", sort of a fail-safe. Here's the test. When you first fire up the truck and drive off, the fan should sound like a jet engine until the clutch warms up and releases. Then it will sound more "normal". It's very common for these things to fail. You could pull the blade off and drive a limited distance and see how the truck reacts. On a cold-ish day you should be fine.
So far, nothing i have tried has worked. I have swapped the heater hoses around on the heater core, flushed the heater core, ran it with the fan off, and, today i even blocked the bottom half of the radiator with cardboard and drove a 100 mile round trip, and still very little heat. Even with the radiator blocked, the gauge never goes past roughly 150, and my scanner, viewing live data it never went above 155, so, i am starting to think the water pump has been switched to a high volume/high pressure one.
 

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C'mon Dodge - NEW DAKOTA
2003 Dakota Club Cab Sport 4.7L
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670 Posts
If the radiator is clogged it usually would run hot, not cold. Never the less, run the truck 15 minutes and then feel the radiator. If it's clogged, it clogs up from the bottom. That portion of the radiator should feel noticeably cooler to the touch than the top. Also could try blocking the TOP half of the radiator.

Not sure, but seems dubious that a high volume water pump would make that much of a difference.

I also recall some discussion regarding aftermarket thermostats not closing correctly in that engine, so try a Mopar branded stat.
 
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Gen 2 Dakota fan
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113 Posts
Discussion Starter · #11 ·
If the radiator is clogged it usually would run hot, not cold. Never the less, run the truck 15 minutes and then feel the radiator. If it's clogged, it clogs up from the bottom. That portion of the radiator should feel noticeably cooler to the touch than the top. Also could try blocking the TOP half of the radiator.

Not sure, but seems dubious that a high volume water pump would make that much of a difference.

I also recall some discussion regarding aftermarket thermostats not closing correctly in that engine, so try a Mopar branded stat.
The thermostat is an OEM from the dealer. Today, I completely flushed it with hot water through the entire system, then, use Preston's super flush, took the thermostat out, filled it with hot water and the super flush, ran it 20 minutes, then, drained it, put the thermostat back in, filled it with water and another bottle of super flush, ran it another 20 minutes, then drained it, ran clean hot water through every hose, then, put another new OEM thermostat in it, filled it with antifreeze, and it is still exactly the same. I'm at a loss for what to do next. With the thermostat and new antifreeze in it, the upper hose reads 163, the lower hose reads 158, and the heater hoses read 161 and 159 after a 100 mile round trip.
 

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Gen 2 Dakota fan
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113 Posts
Discussion Starter · #12 ·
When I fill it, I use a burp funnel with the front end jacked up to purge the air.
 

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2003 RT (5.9)
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449 Posts
Well, here is a 205 degree thermostat

al though I have a feeling that wouldn't be the fix either.

At the risk of sounding flippant, look on the bright--at least your problem is that you are running too cool as opposed to running too hot. Every so often there is a post from someone who has thrown the kitchen sink at his cooling system & things are still roasting. I'd rather be in your shoes than theirs.
 

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Gen 2 Dakota fan
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113 Posts
Discussion Starter · #14 ·
Tomorrow I am going to connect the heater hoses together to bypass the heater core, and see if that raises the temp gauge. As for not having enough heat, where I live that is a huge problem. We get snow and ice, and, today with it above 40, I couldn't get enough heat to keep the fog off the windshield while driving, so I had to keep wiping it off with a towel enough to be able to see. Thats not fun when you are driving at highway speeds.
 

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2003 RT (5.9)
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449 Posts
Oh, I hear you, and I wasn't trying to make light of the situation. Just that I'd rather deal with than than an engine that goes into melt-down ten minutes after it's been started.

But yeah, I can see where you are coming from & I hope you can get this resolved.
 

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Gen 2 Dakota fan
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113 Posts
Discussion Starter · #16 ·
Oh, I hear you, and I wasn't trying to make light of the situation. Just that I'd rather deal with than than an engine that goes into melt-down ten minutes after it's been started.

But yeah, I can see where you are coming from & I hope you can get this resolved.
My next idea, even if it's only temporary, I have a fan from a 94 Dakota 3.9, and since the clutches are the same for that 3.9 and my 5.2, I'm gonna put the 3.9 fan on it, run it and see what happens. If it works, I'm just gonna get another fan clutch, put my fan on that one, and swap them depending on the season. I do tow with it in the summer, so I definitely don't want the smaller fan on it then.
 

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All I can add is welcome to the club. Same issue with my '97 3.9. I have even blocked off the entire rad with little change. However I can offer this. I have a '92 project Dakota with the 3.9 and 5 speed no AC. Seems like the temp runs about the same as my '97 but has plenty of heat. The difference is the '92 has the older and simpler slide controls, not the newer overly complicated vacuum control. Could that be the answer? I don't know.
 

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A recent thread discussed a very similar problem. See this thread:
I have a 99 Durango with a 5.2 with 142,000 miles that has an odd heat issue. The gauge never goes much past 140, even on warm days. Last week, i replaced the thermostat, and it got a little better, but, the only time it really has heat, which isnt much, is during city driving. Once i get on the highway, it slowly gets cold, and then stays that way, unless i pull off the highway and let it sit at idle for at least 15 minutes. It has done this since i have owned it, which is why i finally tried changing the thermostat with an OEM one to see if that would fix it, and nothing really changed. Anyone have any ideas on what it might be?
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I have a 99 Durango with a 5.2 with 142,000 miles that has an odd heat issue. The gauge never goes much past 140, even on warm days. Last week, i replaced the thermostat, and it got a little better, but, the only time it really has heat, which isnt much, is during city driving. Once i get on the highway, it slowly gets cold, and then stays that way, unless i pull off the highway and let it sit at idle for at least 15 minutes. It has done this since i have owned it, which is why i finally tried changing the thermostat with an OEM one to see if that would fix it, and nothing really changed. Anyone have any ideas on what it might be?
I think that you are looking at the issue in the wrong place. You are complaining at the lack of heat in the cabin. I don't think that there is anything wrong with your cooling system. I have a Durango 98 with the heavy duty cooling option 4x4. In central Florida where our normal winter is 65 high and 45 low, my gauge is always half way between cool and redline. It never gets hotter with those outdoor temperature.
My sugestion is to check the cabin heater valve, and for a dirty heater core. Meaning the airflow trough the heater core is reduced, also check for the air blend door, it may not opening fully.
 

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Gen 2 Dakota fan
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113 Posts
Discussion Starter · #19 ·
I think that you are looking at the issue in the wrong place. You are complaining at the lack of heat in the cabin. I don't think that there is anything wrong with your cooling system. I have a Durango 98 with the heavy duty cooling option 4x4. In central Florida where our normal winter is 65 high and 45 low, my gauge is always half way between cool and redline. It never gets hotter with those outdoor temperature.
My sugestion is to check the cabin heater valve, and for a dirty heater core. Meaning the airflow trough the heater core is reduced, also check for the air blend door, it may not opening fully.
It isn't just the lack of heat in the cab. It's how low the gauge is, since this doesn't have the heavy duty system, and, doesn't have the tow package, and, after owning 3 99 Durango's, 6 91-95 Dakota's, and two early nineties rams, I'm well versed in how the cooling system works, and, none of those have ever ran below 180 at the hoses even when it's 90 degrees out, and, on this one, it's never above 164 at any of the hoses, no matter what the out side temp is. The heater hoses are always within 3 degrees of each other when tested with an ir reader, so I doubt the heater core is plugged. This one, unless we missed it the dozen times we have looked at it, doesn't have the cabin heater valve, and doesn't have A/C either.
 

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Gen 2 Dakota fan
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113 Posts
Discussion Starter · #20 ·
I always forget to mention a couple things. This isn't a new problem. I ended up with the Durango 3 years ago when my dad passed away (he bought it when it was a year old), and, the heat and the gauge were that way when I got it. According to my step-mom, this has been an ongoing issue for the last 10 years, and, my dad replaced the water pump twice, the fan and fan clutch twice, the radiator, heater core, all the hoses within the past 6 years. And it only has 142,000 miles on it.
 
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