Engine runs cool around 140 degrees

ABE17

MEMBER
1999 DODGE DURANGO
5.9L
V8
4WD
AUTOMATIC
180,000 MILES

Replaced radiator cap, thermostat, flushed system with flush kit, back flushed heater core to get more inside heat. Engine is running around 140 degrees, never gets any higher.

Saturday, December 12th, 2020 AT 7:02 PM

5 Replies

KASEKENNY

MECHANIC
18,907 POSTS

I have a couple questions. First, have you used a laser temperature gauge to check the engine temperature? For an engine to run this cold all the time, the cooling system would have to be very efficient or the temperature sensor is wrong.

https://www.2carpros.com/articles/how-to-use-an-infrared-temperature-meter

So let's check this with a gauge to see if it is about 140.

If the coolant is not getting very hot then that could be the cause of the no heat inside the cabin but even at 140 the heater core should still be hot. However, let's tackle the coolant issue here and then we can get a new post started if that does not solve the heat issue as well.

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Saturday, December 12th, 2020 AT 7:26 PM

ABE17

MEMBER
3 POSTS

Just purchased an infrared thermometer today, and came to top heater hose 130, head was 160. The heater does put out warm air, when I back flushed it, it got a little better, didn't think of getting temperature of air coming out. It is hotter then body temperature.
I've been thinking the clutch fan, maybe cooling engine down, so it doesn't get hot. Is this possible? I can turn fan went cold, before I start with a little amount of pressure.

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Saturday, December 12th, 2020 AT 9:11 PM

KASEKENNY

MECHANIC
18,907 POSTS

Okay. That is great. Can you tell us if the fan is running constantly? You are correct that a fan running all the time will keep the temperature down. It should not turn on until the engine is warm or the A/C is on. Is there a roaring noise when the engine is running? You have what is called a viscous fan clutch which means it should only be engaged when the temperature is high enough so if it is running when the engine is cold then you need to replace it.

Here is a guide that helps with this:

https://www.2carpros.com/articles/fan-clutch-symptoms

Let us know. Thanks

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Sunday, December 13th, 2020 AT 4:16 PM

ABE17

MEMBER
3 POSTS

Purchased a Dodge thermostat from dealer. Installed it in my Durango now gets up to 195 degrees. Didn't think there would be any difference between an auto parts store and a Dealer thermostat except the money. Everything I did helped a little, back flushing heater and new clutch fan and thermostat. Think thermostat was most important. To bad the 2 or 3 thermostats from parts didn't work in the first place.

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Thursday, December 17th, 2020 AT 8:50 PM

KASEKENNY

MECHANIC
18,907 POSTS

It's funny that it turned out to be that. I was going to mention that it could be the thermostat but immediately discounted it as it is unlikely. I bet the thermostat that you had was a 140-160 degree. More then likely it was mis-boxed or just a sub standard product.

Thanks for the follow up as I am sure that will help others (including me) in the future. Thanks for using 2CarPros.