Fortunately NO! The sensor only reports back to the Computer what the temp. is inside the engine... the thermostat mechanically opens and closes at a set temperature... it is not opened or closed by the computer... it operates according to the temperature of the water that is circulating around it!as long as you do not have any blockages, leaks, bad water pump, or thermostat your engine will not overheat reguardless what the computer trys to do because the thermostat will open and close when it's supposed to!

The Temp. Sensor sends information to the computer so it can adjust the fuel output for fuel economy purposes as well as optimal operating conditions... yes if its sending a signal saying I'm cold the computer will add more fuel but that will only hurt your fuel economy... again because the thermostat acts independently from the computer!

Hope that answers your question! As to the question about the low temp condition... I used to be a Store Manager for NAPA and if I remember correctly the thermostats we sold had on temperature for which each individual thermostat was rated... is nothing is wrong with your wiring to the sensor i know this may sound like I'm talking down my nose but I promise I'm not (not everybody has the time or the patience to look for markings like that but if you're trying to be the best you can be behind a parts counter you wind up noticing quite a few things others skip over, plus, I'm guilty of this myself, all to often we trust the guy behind that counter and we shouldn't haha!)... you may want to look and verify you've got the right one and even after checking for stampings of the temp rating theres no mistake to be made if you do the age old pot of water test on the stove then you will know exactly what temperature that puppy is opening and closing! All you need is a stove, a pot of water, your thermostat, and your wifes cooking thermometer. Put the thermostat in the pot of water place the pot on the stove, turn it on and wait till you see it open check the temperature of the water using the handy dandy thermometer you stole out of your wife's cooking utensils drawer notate the temperature then turn the stove off and wait to see when the thermostat closes check the temp of the water again and presto you know if its not only the right thermostat for your application but also whether or not it's working properly!

I agree with what's been said by every one else... the cooling system on these trucks arent all that complicated you've got your hoses, radiator, fan, fan clutch, water pump, thermostat, sensor and the wiring to the sensor... and really there's only 3 things that I've ever heard of causing a cold running temperature and that is either the thermostat, temperature sensor(s), or the wiring to the sensor(s)!

Hope this is helpful and doesn't feel preachy! Cause Helping not Preaching is my intention!

 

Broken: Not preachy at all someone will do a search on here and your answer will probably save them a lot of time. I was 99% sure that the ECT temp sensor was not causing my engine to overheat that it was the T-stat but since the topic was started figured I would throw that out there. Because I have a digital gauge and it is showing 225 and the factory gauge barely is going over the first little mark on the factory temp gauge, but trust me you can tell it is overheating by the heat and smell the digital gauge is awsome to have. Overheating has got to be one of the hardest problems to figure out because it is a simple system but there are a TON of variables. Hope the OP got something out of this as well.

 

Yeah overheating is definitely a different story... that can be caused by several things... thermostat not opening and closing is easy to verify with out taking anything apart just hold your hand on the upper radiator hose till the engine warms up you should be able to feel it flowing periodically if the thermostat is opening... also pay attention to your fan wether or not its kicking on and off... if you do any amount of off roading it can also be as simple as pressure washing the radiator fins to get all of the dirt and grime out... You may have a gummed up radiator and it may be in need of a good flushing! Regular Anti-Freeze and the Extended-Life Do Not Mix And Will Turn Into A Gummy Substance Do Not Mix The 2!

Heck I've even heard of the rotor (or whatever you want to call it) on the inside of the water pump coming off due to a poor rebuild... I recommend a brand new one from NAPA they come with lifetime warranties... and unlike some other brands it's a true lifetime warranty not a 2 week warranty because you're not changing the NAPA pump again every 2 weeks several times before you finally get a good one lol Ya'll know what I mean! I can see you knodding your heads and rubbing those knuckles from the times your wrench slipped! Just kidding about the knuckles!

Check the weep hole on your water pump if you see a greenish residue around it change the pump before it goes completely out on you don't wait and chance it... you'll regret it if you do! Another tid bit make sure you are getting the correct pump for your magnum engine! Magnum Engine Pumps Spin REVERSE of the Pre-Magnum Pumps Make Sure The Fins On The New Pump ARE THE SAME AS YOUR ORIGINAL! The Magnum Engine water pump comes in 2 varieties a Bolt-On Pulley Or A Pressed-On! Either Style will fit a 3.9L V-6, 5.2L V-8, And 5.9L V-8... I recommend If you have the bolt-on pulley style pump stay with it unless the pulley is damaged... reason being they are easier to work with when taking off the fan clutch!

I've got around 113K on my 00' 1500 3.9L I have Flushed the system using prestone radiator flush twice now. Once because it had never been done and then the second time because I needed to replace the water pump and I wanted to not have to worry about it! I have only replaced the water pump once due to seeing anti-freeze residue trails around the weep hole I also replaced at the same time my upper and lower radiator hoses the short bypass hose that gose up to the intake manifold right next to the thermostat housing as well as the thermostat due to seeing a small pool of antifreeze in that area... I changed those things more as a piece of mind to protect the new water pump more than anything else... however I did have to replace my belt tensioner because when I placed a socket on the pulley bolt and released the tension on the belt the tensioner did not spring back into place whatsoever! I've always used the prestone universal antifreeze it's an extended life formula thats is capable of providing proper lubricity to all of the parts within your cooling system!

Aayways back to the original thread if its running cool its gonna burn more fuel because it thinks you're in cold weather and its trying to get up to normal operating temp! I know that it's a pain to get to but I'd be suspicious of the thermostat either sticking never fully closing, or being the wrong one because they do make 160 deg. thermostats for these magnum engines! If that's working properly though then I'd fall back to either the temp sensor or the pigtail to the temp sensor! Make sure that the ground wire has good ground and that with the key on you are reading 5 Volts at the positive wire in the pig tail!

The Factory Service Manual for your truck lists 5 possible reasons for a temperature guage reading low and here they are:

1) Has A Diagnostic Trouble Code Been Set Indicating A Stuck Open Thermostat?

Take it somewhere that will check the codes for free like autozone or someplace like that!

2) Is The Temperature Sending Unit Connected?

Check temperature sensor connector. Repair connector if necessary.

3) Is The Temperature Guage Operating Ok?

Check guage operation. Repair as necessary.

4) Coolant Level Low In Cool Ambeint Temperatures Accompanied With Poor Heater Performance.



5) Improper Operation Of Internal Heater Doors Or Heater Controls.

Inspect heater and repair as necessary.

There is a copy available of this manual here on the forum! The link is:

https://dodgeforum.com/forum/2nd-gen-...tmas-guys.html

 

hmmmm I know it is not the issue because the entire cooling system on my truck is new (hoses, water pump, radiator, t-stat, heck the engine is even brand new) but I used all brand new prestone 50/50 mix but I "think" i may have had some extended life left over and mixed a little in. I don't think it would have turned into a gummy substance yet because the truck only has about 100 miles on it I will check if I did I will get it flushed once I get the T-Stat in.

When the engine was hot the top hose was hard as a rock I know that!!!

 

Depending on what flavor of prestone 50/50 you may have been using the same stuff... I prefer to get the straight stuff instead of the mixed because back when I worked at NAPA the 50/50 was almost the same price as the straight! I dont like paying for water! paying for antifreeze im ok with but not water when I can get tap water thats pennies per gallon I'll do my own mixing thanks anyways prestone! lol Check both your bottles cause the 50/50 in the yellow bottle i believe is the same universal stuff as the straight stuff in the yellow bottle that says any make any model! 100 miles you're probably right however I have no clue as to how long it takes that reaction to occur some chemical reactions take longer than others! however definitely check to make sure theres circulation through your top radiator hose! if not something is either plugged up, broken, or stuck in the closed position and you'll never get it to run properly till its fixed! Good Luck Hope I've been able to help with what little parts knowledge I have imparted! And make sure both you guys post what was wrong!

 

hmm.. my top hose and the bottom hose get hard as a rock when the truck is running. and i know it gets to temp because it goes up to the 195 mark then you see it drop down to what it is in this picture

is that 160ish?
oh, i've been getting crap mileage for a little while now too, with the old thermostat and the new. bad temp sensor maybe?

 

Friend I'm not the Expert on the subject but my trucks needle has always since it was new been approximately the same position as what yours is showing in that picture I believe if I'm not mistaken that the 160ish mark is the one right next to the 130 mark. I could be wrong about that but I do know mine has always been about the same as what yours is showing!

Anyone else have a different reading on their guage when your trucks running normal?

 

mine used to sit here no matter what the outside temp was until i put a new radiator in it.

 

what brand radiator did you go with.. mine has a hard time heating up.. as in i have never had a truck that i could get it hot in their. not like my car... on the other hand it does get comfy but thats about it..... i also have a newer rad in mine from a 2001. and have factory tow package...

 

Whichever one they keep in stock at advance. I think it was something like 130$.
Mine doesn't have a bit of trouble heating up. on a cold day, letting it warm up for about 30 seconds to a minute before I go, it'll be blowing warm air in 3 miles and hot air in 5 (at operating temp).