No heat issue

First off I know there are probably plenty of posts with similar issues but I’m out of town and looking to pinpoint this issue and haven’t been able to find the same problem.
I think I have a thermostat issue.
2010 2.7L 5 spd
I live in NY
Stopped at a rest area and when I restarted the truck the engine temp went up slightly but I had no heat. As soon as I gave it throttle, engine temp went back to normal, still no heat.
I had somewhat warm air a couple times when driving and engine temp stayed normal. After shutting truck off I watched coolant temp and it rose slightly again.
checked coolant hoses, bottom hose had no pressure and top hose felt stiff.
Coolant reservoir was at max level line before the trip but was filled all the way up to the cap when I stopped. Also noticed some bubbles slowly entering the reservoir when checking things over. I have found no leaks so far.
Checked oil didn’t notice any coolant in the oil or oil in the coolant.
Any help would be great, just trying to fix this issue and make it home in a couple days

 

If your coolant level in the radiator is ok, I might suggest a new radiator cap but it sounds like a sticking thermostat to me (if it's not something more serious).

 

Check the coolant in the radiator not just the overflow, sounds like it might be low.

 

could be a clogged heater fore...feel the heater core hoses in the engine bay...

 

Sounds like the thermostat is stuck or the heater core is clogged up. I'd drain and flush the entire system. Also, remove the thermostat and replace while you're at it. They don't cost much.

 

I wouldn’t do anything until I checked the fluid level in the radiator.

 

Thanks everyone I’ll check the radiator level first thing in the morning and move of from there appreciate the responses

 

Morning is the best time to check coolant level, in both radiator and expansion tank. And watch over time to see if the level is dropping gradually

Number 1 cause of poor heater performance is a low coolant level, often from a leak somewhere

Thermostats rarely fail these days

 

I have an 09 2.7 SR and had a similar problem as well.
There was a service bulletin for 09 models where the foam cover came unglued from the flapper and blocked the flow of hot air. It involved taking the dashboard off and taking apart the hvac system (big, big, job) i did this, but the flap was fine. D'oh! Many hours spent on my back admiring the hvac solenoids.
I replaced the thermostat at the same time, and i have a haunting suspicion that that was the culprit all along. Don't be an idiot like me. If that's your original thermostat, just replace it. It's going to pack it in sooner than later. Keep us updated. Be aware and get any air bubbles out if you change your coolant. I do have a very good understanding of the hvac system in these trucks, however! I do wish it was easier to work on!

 

Update: started the truck this morning, radiator looks like it might be low, reservoir tank is still over full(it wasn’t before the heat went out). Both heater core lines through the firewall were warm. Ran truck for around 20 minutes with radiator cap off. And never got past 1/4 on the temp gauge. It would actually drop I small amount if I gave it throttle. Had some heat this morning. The two main radiator hoses never got warm. Going to pick up a thermostat and drain and fill the system. I’ll update again later and thanks again everyone, not fun breaking down away from home.

 

Doolars to donuts, your thermostst is stuck open. I'm curious as to why the resevoir would overfill.

 

If there is a leak somewhere the coolant will get pushed into the expansion tank when warming up, but when it cools down instead of sucking the coolant back into the radiator it will suck air in through the leak. So you end up with empty space under the rad cap and too much coolant in the exp tank

 

Woofer2609 that’s what I’m leaning towards, and the overfilled reservoir had me wondering to.

 

Also, running the engine with the cap off is OK for a few minutes but the system needs a little pressure to flow correctly and get up to temp. The cap needs to be on after a few minutes in my opinion.

Or get one of those spill funnel/buckets with the stopper plug. They're a great way to watch bubbles come out and feed coolant in. The stopper can simulate a cap and get things flowing

 

I’ll check again for leaks but haven’t found any yet

 

You checked for a blown headgasket?

 

Pick up a new radiator cap while you're at it. Those wear out over time too.

 

Get a block test kit

 

Good call. Milky oil and/or lotsa steam from the tailpipe that smells like maple syrup are good indicators.

 

I’d take some of that coolant out of the overflow reservoir. Once you fill the radiator to the top and drive. You might end up with the reservoir itself over flowing.