Ok. Since I bought my truck a few months ago (around June) I have noticed this problem. I switched the t-stat just b/c it was easy and i wanted to flush the coolant anyways. After doing that, the same stuff still happens.

When I go down hills my engine temp goes far down (imagine a 1/4 mark on the temp gauge) and when I go up hills or if it's a hot day (95+ degrees), the gauge will go above the half mark (sometimes up to 3/4 depending on temperature outside and hill involved).

I am tired of this happening and want to fix it asap. Would this be a faulty water pump? I want to switch to a flex-a-lite fan, but want to fix this variable first.

Please help me out with this.

The truck has 58K on the odo. I have new plugs and change the oil about every 3k.

 

Long shot but it just might work:

There is a bleeder screw on the radiator intake hose at the block. Large hex if I remember correctly.

Perhaps the stat was installed basackwards ????

Another thought: If you used a coolant additive with the OEM coolant; you most likely have a crusty build-up in your radiator core and block. Please don't ask me how I know this to be true !!!

Remedy: new radiator AFTER multiple flushings with several brands of flush products. Gets the crust outa the block but not the radiator.

 

im not sure if it is that big of a problem or not... my 08 stays in a steady place but when climbing hills, on a hot day, it will go past the half way mark, then coasting down a hill for a little distance it will drop below its normal position i think it may be because of the operation of the fan clutch, but a e-fan may help if set correctly, or my SC 3865 has an option to set the fan engaugement but i havent messed with that yet... either its a normal thing, or we both have the same problem

 

thanks for the response. I'm pretty sure the t-stat was not installed backwards as the problem stayed the same before and after the t-stat install. I used replacement coolant that NAPA told me would work for the Dakota. I used a 50/50 mixture. No coolant additive.

What do you mean the 'bleeder screw'? I guess I know what a bleeder screw does, but how would that fix my problem? :sorry if that's a stupid question:

 

1. Try replacing the thermostat.
2. Check the water temp sensor and its ground. Its just below your Map sensor on the block.

 

Ya, I don't think it is backwards. It's a new stat, and the old one did the same thing so I don't think that's the problem.

What else would cause this thing to fluctuate so much? I have had other vehicles where the needle would stick in one spot not matter what was going on (hill, temperature, load, driving habits, etc.)

 

Have you checked the water temp sensor and wiring? Could be a bad sensor or improper grounding of the wire.

 

THANKS! I have not checked this yet. I will try and report back :-) Thanks again. We will see if this works!

 

i dont think you have a problem, for quite a few years now, dodge had a bright idea to put the temp sensor somewhere else than colse to the thermostat, so even though the t-stat is regulating the correct temp, there are other hot spots in the engine that can show up on the gauge, under load or even on warm up, my diesels did it so bad (sensor mounted on the rear of the head) it finally irritated me enough, i moved the sensors to the t-stat housing, and the gauge doesnt bobble at all, just a thought...