Help diagnose overheating / heater problem

Truck overheated for the first time in a long time today while sitting in bumper to bumper traffic. It did it a few months ago in uphill bumper to bumper traffic. Temperatures returned to normal upon getting back up to speed.

Later in the same day, the heater started blowing cold air. Stopped for gas (truck shut off for 10 mins), got back on the road, and the heater started working again.

I'm thinking that the thermostat is sticking and needs to be replaced. Any other insights on this?

 

Sounds like you are on the right track with the thermostat. Replace it and see what happens.

 

Sorry to hear about your troubles. I would first check to see if the thermostat is stuck. Does the engine take a long time to warm up (as indicated by the temperature gauge or heater operation) the thermostat is probable stuck open. If the engine runs hot, use your hand to check the temperature of the lower radiator hose. If the hose is not hot but the engine is the thermostat is probably stuck in the closed position preventing the coolant inside the engine from traveling through the radiator. In both cases replace the thermostat...
Good luck....keep us posted.

 

Change the coolant and thermostat and report back.

 

Update:

Drained coolant from radiator, reservoir, and passenger side drain on engine block. Could not locate the drain on the driver's side and the coolant was fairly new and very clean, so I said screw that driver's side drain. Ended up getting just a hair shy of 2 gallons out of the truck.

Replaced thermostat.

Refilled with toyota coolant.

No issues so far. Truck is reaching operating temperature a little bit quicker and is definitely blowing hotter air when set on heat. Not overheating and coolant levels are stable after letting it run and topping it off.

Hopefully that was it.

 

Good Job - Well done! Did you take any pictures of the process for folks to see? Its always a help when others run into the same difficulties.
Glad to hear its working!