You said you aren't losing coolant, but you do have air in the lines. You need to bleed your system. Click on the sticky for the correct procedure, but here is how I do it.

First, make sure your bleed screw is NOT in the middle of the top hose. If it is, replace the hose with the new version becaue if you try and take off that bleed screw after 98k miles, it will most likely break. The new version of the hoses has the bleed screw at the junction of the hoses.

If you are good there, undo the resevoir tank (it just pulls up towards the front of the truck) and raise it up higher than the bleed screw. Undo the bleed screw and add coolant into the resevoir tank until it comes out the bleed screw. Once it starts to come out close the bleed screw and put the reseovoir tank back. Fill er up with coolant and see if that fixes your problem.

 

Ditto on the bleeding, gurgle gurgle. The t-shaped hose will help too. The challenge is the gurgle could lead to overheating someday or the lack of heat in the cabin.

"Ok Honey, this is what you do if that little red light comes on..."

Good thing to have done before you deploy.

Good luck, stay safe.

 

Excellent tips here, guys. I'll get under the hood and check bleed the system, as well as check the throttle body heater. Thanks!

 

I was having a similar issue on my 2001. Ditto on the tips listed. We also swapped the two smaller hoses that go into the firewall for the heater core, that too seemed to help. Just swap one for the other, completely, not just one end for the other end. Phil