my truck engine does not heat up. stays in the cold temp reading area

It sounds like the thermostat is stuck open. Does it heat up when parked and cool down when on the highway?

second that.

It will only heat when parked and the engine reved for several minutes. The temp gauge drops a little when the heat is turned on, but it goes all the way cold when driving... even with the extra burden of the AC unit running on max. I thought it was the thermostat as well, but someone told me to check for a clogged heater core first. I really have no intention of replacing the heater core on my own with all the work involved with just getting at it. Thank you both for the insight.

If the heater core was clogged, the hoses would be cool or cold. You would have less heat coming out of the ducts. It wouldn't effect the temperature gauge on the dash.

definitely a stuck open thermostat. get really cold on the highway and if weather is hot it may rise to close to normal while idling and go way down on highway...if weather is cold it will likely just stay cold all the time. the truck will not go into closed loop (probably throw a code that engine is too cold too long) which will cause the vehicle to run really rich (closed loop) and get poor mileage...mine went from 15mpg to about 9mpg. I had a 1 year old thermostat when it stuck open...crap china junk! BTW your gauge should be about 1/3 of the way up the gauge when working properly. when my thermo was stuck in 50 degree weather, it would rise to no more than 1/8 of gauge and go to full cold on highway. *running the engine this way will not only give you poor mileage, carbon deposits in motor and foul spark plugs but it will burn out your catalytic converter by running so rich in closed loop. Closed loop runs off a safe (temporarily) rich condition and disregards most sensors that help to protect the cat. open loop uses all sensors to constantly adjust fuel and timing to get optimum air/fuel ratio, best mileage and most power. Hope this helps someone! Its a bit of a pain to change the thermostat so buy a top quality or OEM one, also buy a new, top radiator hose, hose clamp and thermostat inlet tube (metal flange and tube that bolts to manifold and connects to radiator hose, mine was rotted out and leaking a bit, yours will be too and its cheap insurance to not have to do this job again. takes about 1.5 hrs all together and a good time to do an engine flush and coolant change. if you have been running it this way for awhile, you may also want to do a seafoam decarbonize treatment through intake first and then change plugs. Remember, these trucks run best on champion plugs listed on the emission sticker...i've tried them all in the 330k miles ive had my ram and copper standard champions are the way to go! no platinums or anything else or your pinging will be worse. ALSO: I had my PCM go out a year ago and bought a new one with the newest program and It actually solved my pinging problem! (i have a slight intake plenum gasket leak since 65k miles but not time to fix it right being my daily work truck) I used to have to use premium all the time to keep it from pinging heavily under load. Now, no ping on regular unless its really hot and towing heavy up a big hill and its still very very light. So reprogram your current PCM at the dealer (about $100) or Just order another to swap out (about $165 on carid)

I have a 99 ram 1500 with a 360. I have replaced the heater core, thermostat 3 times and still will not heat. I have the the front completely covered and a even the rad is covered and still will not heat.What is wrong with this engine

Duane, same here. 99 ram 1500 van and stays right at 150-160. Radiator covered, quick clamp on the hoses, sit there with it idling for a half hour etc. just won’t build temperature. Sucks gas hardcore, blows air respectfully to the temp gauge (sort of warm at best) and rear heat is almost non existent. When I floor it, You can hear a pneumatic valve actuating and it blows nice and hot. When I first noticed the temperature problem the coolant level in the reservoir was very low and you could hear a squealing sound coming from the Water pump. I topped off the reservoir and the radiator, squeezed the upper hose a bunch of times and watched lotta bubbles come out. After getting a lot of the air out the water pump stopped squealing. I’m thinking there’s air stuck in the system somewhere, but that wouldn’t explain the low temperature problem. I don’t think it’s a thermostat stuck open problem because the temperature would have built up idling in the driveway with the radiator covered.

I have a 2000 360 and I just replaced the thermostat and water pump and mine still won’t heat up to 150 at best temp don’t change if driving or parked don’t know where to go next but the heater box

My 1998 5.3L runs well but wont get over 130 degrees. I can't figure it out either.

Could be coolant sensor or sender for some of yalls issues.