jumpinjivinjoe

Here's the story...

I just drove 1000 miles with a GCVW of 19,000#. Everything went well despite being full throttle often.

I noticed that I didn't have any cab heat on the trip. I thought maybe my heat/cool valve was not working since my engine temperature gauge was at the low end.

After that long trip, I went to run errands today without my trailer and found my temperature gauge was showing my engine was overheating (230 degrees). I tried running at idle but it didn't cool down. I cracked the radiator cap assuming I must have had a no coolant and maybe a 1 gallon of coolant sprayed out. I sealed the cap again and let the engine cool down before adding another three gallons of coolant. It took about 1 1/2 gallons through the top hose of the radiator into the engine and then another 1 1/2 gallons in the radiator.

When I drove the truck again, it ran around 190 degrees and sometimes quickly dropped to around 175 only to go up to 190 again; this is still way too hot since normally the gauge shows around 160 even when towing. However now my cab heat works and blows hot.

No coolant in oil and oil in coolant as far as I can see.

I have a critical job and am out of town so I need to resolve this ASAP.

What should I troubleshoot? What could the problems be and how should I check?

AlpineRAM

The stock thermostat in these trucks is either a 180 or a 190F T-stat.
So seeing you running at 160 or less points towards either a bad gauge or a bad t-stat.
You seem to have run the engine at extremely low coolant level, either you had much more than a gallon come out of the cap or - 2 gallons low meaning no cab heat, and an always low temperature indication because there is no water getting up to the sensor.