I had this same problem last year. My thermostat was stuck wide open, after I replaced it the truck heated right up to normal operating temp. Thermostats are cheap and easy fixes. There is a good article about replacing one in the DIY section. When your engine is at normal operating temp your gauge should be right on 200, or just to the left of it.

 

I already replaced the thermostat and the problem is still there, thank you though.

 

Yah it very well could be a stuck thermostat even though you just changed it. Like everything some thermos are doa. Your heating condition sounds just like mine was before I changed the thermo and flushed the system. If I remeber you dont lose all that much coolant by pulling the hose of the top of the thermo. Its always worth a shot changing it out again since they are only a couple of dollars. Plus if it does turn out to be bad you can return it if you want.

 

Is it possible that i did not get the seal around the thermostat to seat right and that could be why the new one isnt working? Im sure thatI put it in right, but you never know i guess.

 

That could be possible. If you didn't seat the seal right coolant could easily just leakright past the thermostat. Like swartlkk said earlier, the thermostat is the master controller of the coolant temp.Try driving around for 15+ minutes (plenty of time to let the engine warm up completely) thenfeel your upper radiator hose to see if it is hot. If it is hotthen your thermostat is working and this could be just a faulty temp sensor..

 

OOPS....not sure if this makes a difference or not but there is a typo in my first post. The engine temp gauge is not showing 100-110, it is more like 150-160 probabaly (hard to tell since the gauge isnt equal). Anyway, i made a mistake, not sure wehre the 100-110 came from.

I will check that hose after i drive home from work tonight. But if it is warm and its just a faulty temp sensor then that still wouldnt explain why my heat isnt working. And i've checked the 2 hoses running in and out of the heater core and they appear to be about the same temp.

 

150-160 could be a bad temp sensor as said above or as you said your gasket might not be properly seated. If after hours of driving at 65mph the wholesystem should be 195 unless its like -15 out. When your truck is heating up the first time the thermostat opens does the gauge drop say 20-50 then warm back up to 160 or does it seem to just stay at 160? If both of the heater core lines are the same temp then it seems to fall back to the thermostat. Did you pry the thermostat out with anything or did it come out easily also did the gasket mating surface look smooth where the thermo goes? Also just to check since you said the gauge goes to 160, is the thermostat a 195* thermo and was it the cheaper one or the one for a few bucks more than the cheapest?

 

The clarification on the temperature leads me to believe that there is air in the system. This is typically the gauge reading when there is steam at the gauge and not coolant.

 

Once it warms up to 160 it will drop some and then go back up. It will actually fluctuate 10-20 degrees alot while driving actually depending on if i am sitting idling at a light, or accelerating.

how do i go about getting the air out of the system?

 

Elevate the front end of the truck, with the passenger side slightly higher than the driver. This will allow for the best possible way for getting the air to the radiator cap location where it can escape. With the engine running and the radiator cap off, watch the fluid level and add as necessary. You will want to bounce the truck from time to time in order to shake any stubborn bubbles loose. As the truck reaches operating temperature, some coolant may spill out. You may have to turn off the truck and let it cool, then repeat the process a few times to get all of the air out of the system.