I have a 2001 Dodge Dakota 4.7 SLT 4WD that has just a little over 100,000 miles on it.
I bought it used five years ago and from day one I noticed that it seems to take 15 to 20 minutes of driving for the temperature gauge needle
on the dash to finally enter the low side of the normal operating range. Even after driving 45 minutes to an hour the needle never ever reaches
the straight up position between cold and hot. After an hour of driving and beyond that needle always reads between the 10:00 and the 11:00 mark
in the normal range and never straight up or further to the right toward the hotter side of the gauge.
I'm just wondering if the 15 to 20 minute warm up time is normal for this truck and the needle running on the cooler side of the gauge normal. Is this too
slow of a warm up time? And is a 10 to 11 o'clock reading on the gauge normal at full operating temperature.
I have read that you DO want an engine to reach and run at full operating temperature quickly and that running too cool can be bad on an engine as well as running
too hot. I do get plenty of heat from the heater in the winter time.
I appreciate your insights. I want to avoid replacing a thermostat needlessly if what I am experiencing is normal for my truck.

 

Get a remote infrared thermometer. These are handy and have a lot of uses anyway. Read the temperature on the thermostat housing on the block. Your timing chaian could be slipped a tooth although you have fairly low miles for that to happen. Running too cool puts the computer into "open loop" mode. Since fuel injection doesn't have a choke, the computer injects extra fuel to warm the engine up. Too cool and you waste gas, can destroy your catalytic converter and even get the rotten egg smell out the exhaust.

Since you've had it 5 years, I'd go ahead and change the coolant and thermostat. I always do that when I get another used vehicle then I know when it was done. If you never add coolant, your "antifreeze" portion of the coolant never goes away. After 5 years though, the "anti-corrosion" does break down. On the old solid iron engines, no big deal. On current engines, you get electrolysis eating the insides up.I'll bet when you get in there, someone put a 180 thermostat in it for a richer fuel charge. It doesn't work but that doesn't stop guys from hearing about it on the old hot rods and doing it themselves.

 

Thanks ol' grouch for your response. When I point the infrared thermometer at the thermostat housing what reading should I get?
I did not change the coolant when I bought the truck because it is nice and clear and clean and tests properly; appearing as if it had already recently been changed.
I think I will go ahead and change out the thermostat before winter; even though it looks like it will be a bearcat to change due to where it is located.
The truck starts and runs absolutely beautifully and I have not noticed any rotten egg smell.

 

Should have 190-210ish at the thermostat housing and hot side of the radiator, about 140-150ish on cold side of radiator.

 

Your reading will depend on the thermostat. You aim at the housing against the engine where the hose attaches. Another thing the tool is good for is to look for a dead cylinder. Aim it at the exhaust manifolds and if you have a weak or dead cylinder, the manifold will be cooler where it exits the head.