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My truck runs pretty well but according to the temp guage the temp never rises above 150f. It never goes to 195 first (thermostat opening temp). The temp just warms to 145-150 or so, and stays there no matter how far/long I drive. The heat does warm up after about 3 minutes of driving, and can keep truck occupants comfortable in our mild Virginia winters. The heat is nice and warm but you cannot get it to blast super hot as I can with my other vehicles. Also, even though the heater works fine, the upper radiator hose is always easy to squeeze by hand and does not build pressure no matter how far/long I drive as happens with my other vehicles. System is full of dexcool 50/50, and does not have any leaks.
I am trying to figure out a diagnostic direction here, I do not want to just start throwing parts at it. I can check the fan clutch i guess, and make sure it does not engage fan until engine warms up. but I would think that even if fan runs all the time my engine should eventually be able to get up to 195 but it never does. I can also check the thermostat and temp sending unit(s), I guess.
If it never rises above 150 your thermostat is stuck partially open or your thermostat temp setting is too low. Like. 160 degree thermostat versus a 180 degree thermostat.
Yeah, I would suspect stuck open thermostat if it were me. You could check the housing with a infrared temp gun if you suspected a gauge or sensor issue. Maybe also feel the hose to the thermostat while its warming up. Should stay cool until it reaches operating temp and the thermostat opens up. If it gets warm before that... The thermostat is at least partially open. Also make sure your fan clutch isn't engaged I guess too. Those are my first thoughts.
Thanks very much for your insights, guys. I replaced the thermostat today with a 195-degree thermostat. Temp gauge on dash indicates about 180 degrees now. Definitely an improvement over the max of 150 i was seeing before, but system still seems to be running a bit cool. After driving 20 miles the upper radiator hose still is very easy to squeeze completely together with two fingers. Doesn't seem to be any pressure in system even after driving 20 miles. Also, it seems fan clutch doesn't seems to ever disengage. I can start it up stone cold and fan immediately goes full blast moving tons of air.
Don't rely on the factory temp gauge to give you accurate readings. I have two 98 Chevy trucks and the factory gauges hardly ever read close to what the actual temps are.
If your clutch fan is original it probably needs to be replaced but usually when they go bad they don't lock up and are quiet all of the time.
