Help – 2011 Ford F-150 Heating issue.

As usual I turn to all the knowledgeable people on this site for help. I have a 2011 Ford F-150 and a few days ago my Heater seemed to stop working. It was blowing Hot and just like that it turned to blowing cold. No matter what I tried with the controls I could not get it back to blowing even Warm. Since I was almost home and had a Few other things to care of I just parked it and thought I would go check it out again later. Went for a run to the grocery store a few Hr’s later and it seemed to work just Fine. Next day was doing some running around and once again went back to blowing cold. Doing a quick online search and after getting several possible problems I decided to start with the cheapest fix. The coolant reservoir tank did not show any in it. I stopped and got some antifreeze and filled it to the cold fill line ( It took almost the full Gallon. All the way to work after it blew Hot. Sitting here at work I’m hoping it was just that simple, But with my luck I’m doubting it. What do all of you think that is all it was?. Could it be as simple as being a Gallon low on Antifreeze? One other thinh I did notice is it blows MUCH hotter while at highway speeds than when stopped at stop lights – Is this Normal as well. I guess I’ve never really paid that close of attention to it. Most of the online research I’ve done tends to point to it most likely being a Blend Air Door actuator. Being the mechanical Idiot that I am I’ve never even heard of that. Of course there were a fair # of possible other issues as well. At this time I’m just hoping it was the low antifreeze. I’m going to check the level before I head home after work and make sure the reservoir is still full and then just drive home and see if the problem is still gone. Just in case the problem returns I’ll appreciate any Info. that you all care to share. I just hate to take it into the shop if its just something simple. I tend not to be the most trusting of auto repair shops. Thanks in advance for all of your thoughts and advise.

I’m no mechanical by trade but do work on vehicles fairly often, I think my main concern would be where did you loose coolant? The heater core provides the heat through your coolant lines which get hot from running through your engine. Being low on coolant could cause you to loose heat but now the question becomes how did you loose coolant in the first place. Leak? head gasket? overflow?

Check the neck on the water pump to see if there’s any signs of leaking through the vent found underneath and behind the fan assemble. I’d also check to see if there are signs of water/anti-freeze coming out of the vent tube next to the radiator down low where you’re not apt to hazard a casual glance. Keep on eye on the over-flow can to be sure your water level isn’t dropping over time. It could be as simple as a radiator cap or thermostat but it could also be a blown head gasket. Is the water in the over-flow clean? No gray foam or anything?

lol, I can guaranteed tell you what your issue is. I have a 2011 5.0. My coolant reservoir is currently cracked at a parting line and leaks a very small amount of coolant when the tank is cold (might fix it this summer). The cracked tank is pretty rare, but can happen on the F-150. The USUAL suspect on all of these newer Ford vehicles is the quick connect fittings they use on all coolant lines. I have had to replace two of them on my truck in 20,000 miles. The first one is the T next to the thermostat (most common) and the second was another T coming from the bottom of the radiator. The parts are cheap and it’s an easy fix, just frustrating. Some people also experience a leak at the connector below the reservoir. If that is the leaking suspect, you will see coolant dripping on your steering knuckle. I would inspect that one first, as it can cause issues with steering down the road.

Easiest way to diagnose the issue is to find all the quick connect fittings and wiggle them with a clean paper towel wrapped around them when cold AND warm. If there is ANY sign of coolant on the paper towel, you found a leak. Unfortunately, the O-rings that leak are not a standalone part and you need to buy the whole fitting…