I post this after a week or so of pure frustration and irritation with my 2016 fusion titanium. While I appreciate the feedback and suggestions to some of the questions I ask, being provided information for a 2014 fusion, 2015 fusion, 2015 fiesta, 2013 focus, etc., etc., was not helpful and only compounded the flustration and confusion.
With that said, I believe I have solved the problem and want to share the information with everyone in hopes to save them a lot of their own frustration, time, money, and perhaps solve their problem as well.
Again, this is for a 2016 fusion titanium 2.0 turbo. It pertains to the check engine light (cel) coming on showing cylinder misfire codes and an unexplained overheating issue to where the engine coolant over temperature warning would come on and sound and would quickly lead to a cylinder head over temperature warning that put the car into limp mode. Limp mode is no fun if you're in busy traffic.
My 2016 fusion with 88000 miles on it started acting up about a month after I got it. First issue was the CEL and my code reader said it was a P0304 code popping up. P030X means cylinder misfire and 1, 2, 3, or 4 is the cylinder that's misfiring; thus P0304 means I had a misfire in cylinder number 4. I would reset the code and it would pop back up a day or so later. After scouring the Internet and many Google searches later, I discovered these engines have an inherent problem with cylinder's cracking and allowing coolant to seep into the cylinder and foul the spark plug generating the misfire. This may present itself as a head gasket leak but sadly it will turn out to be a small crack In one of the cylinder walls due to an poorly designed engine.
In addition to the misfiring and overheating, I was ever so slightly losing coolant. The reservoir had to have coolant added added every so often. Wasn't a big loss but it was still going somewhere. The oil was clean and i didn't notice any steam or coolant smell from the exhaust; other symptoms of head gasket/mysterious coolant loss issues. One of the first things I did was go and purchase a combustion gas detector from Harbor Freight. Fairly simple test, you put a blue liquid in a test vial hold it down over your coolant reservoir fill hole. These cars do both have a radiator cap per se. You et the car run and sample the gas/air that's in the reservoir/cooling system. If the blue liquid turns green or yellow, you're getting exhaust gas in the cooling system which is a sign of a cracked cylinder or a blown head gasket.
More research and I found Blue Devil Radiator and Block Seal, available at most any auto parts store. I followed the instructions on the bottle to the letter. DO NOT pour it in the reservoir. Drain some coolant out of the engine by removing the large radiator hose on the right side of the engine. DO NOT do this if the engine is hot. DO NOT remove the reservoir cap if the engine is hot. Having been an emergency medical technician for a number of years and running calls for people that have done such things, responding in an ambulance to find severely burned persons with skin literally hanging off of their faces and arms. You don't want to open these things hot. It gets ugly in a hurry.
Once I had drained some of the coolant out of the system into a catch pan, I reconnected the large radiator hose, took the largest of the 3 hoses/tubes off of the reservoir, stuck a funnel in the end of the hose and poured the entire bottle of Blue Devil into the funnel. I topped the coolant off in the reservoir and put the cap on the reservoir. Continue following the directions on the Blue Devil bottle.
Upon circulating the Blue Devil like it's said to do, I let the engine cool off and reran the combustion gas test. The fluid stayed blue. No combustion gas in the coolant. I was impressed. Once that operation is complete, you now need to deal with the overheating issue. There are two temperature sensors on this engine. A coolet temperature sensor and a cylinder head temperature sensor. Ford engineers ought to be throat punched for where they put the coolant temperature sensor. You have to disassemble several things just to get to it where you can barely see it or touch it. I started with the coolant temperature sensor as it was the cheapest of the two. I was fairly confident the car was not actually overheating but was getting a false reading from one of these sensors. My past experience with overheating cars tell me that they usually show some type of gurgling or boiling in the reservoir, steaming and puking coolant out, or you hear bubbling and boiling sounds. This car wasn't doing that. Maybe in the past. Maybe damaging sensors. I was thinking false sensor readings.
The easiest but more expensive sensor to get to is the cylinder head temperature sensor. See the attached diagram. It's pretty much straight in the back of the engine along the top under a small aluminum foil insulation type cover. Easily pull the cover up the wire to get to the wire connection. Pinch the little clip and remove the wire from the sensor. A 3/4 inch deep well socket will fit this but you have to be very careful as to the connector that's attached to the sensor. It will make it kind of difficult to get the socket down on the hexnut of the sensor. There is no coolant behind this sensor so you do not have to worry about draining the system or any type of leaks. Simply remove the old sensor and put a new sensor back in its place. Be careful starting the new sensor that you don't cross thread it in the hole. Reconnect the wire to the sensor and push the aluminum foil boot back down on top of it.
If you had to put the Blue Devil stuff in the cooling system, you're going to find that you probably airlocked the system and/or your heater core. You will have little to no heat coming out of the vents. The only true way to get all of the air out and make sure it's totally full of fluid is to vacuum fill the system. Another trip to Harbor freight, $89 later and I had their vacuum fill tool for cooling systems. The thing works off of shop air; an air compressor. The kit has several adapters so you could use it on multiple vehicles. You may find that the cone shaped looking adapter will fit snugly in the opening to the reservoir. It will allow you to pull a nice vacuum on the system. First thing you want to do, again making sure that the vehicle is not hot, put the vacuum fill tool on the reservoir. Next, turn the car on but do not start it. You want to adjust the climate control to high on the temperature setting. Just let it sit there while you're filling the system. Keep in mind that this may time out on you in about 15 minutes. If it does it's probably going to close the heater valve and not allow you to completely vacuum the system or allow coolant to flow to the heater core. With the car on and the inside temperature sit too high, follow the instructions for the vacuum valve. Might be helpful if you watch a YouTube video for vacuum filling cooling systems.
In the video he does not mention opening the heater valve but it's important to do that to make sure you get all of the air out of the system. Once it's refilled you can go for the test drive. Hopefully this one sensor solves your problem like it did mine.
On the outside chance it was not the cylinder head temperature sensor and maybe the coolant temperature sensor, you will have to remove move the mass air sensor from the intake air hose, the clips holding the sensor line on to the lid of the airbox, the airbox lid, the intake hose, the base to the air cleaner box, the battery, the battery tray, a couple of clips on the battery tray securing some wiring, a corrugated looking 1-1/2 diameter black plastic hose that wraps around the back of the engine, simply pull it off the front and tuck it out of your way somewhere, and finally a small heater hose at the back (driver's side) of the engine. See the diagram for the coolant temperature sensor location. It is a pain in the ass to get to. Small hands are very helpful. For removing this sensor, you're going to want to make sure that you have drained some coolant out of the system. This sensor is actually in the coolant stream and if you remove it with a full system you will have coolant running everywhere. Once you locate this sensor I found it easier just to leave the wire attached to it for the moment. It is held in the engine block by a retainer clip. I removed the clip using a pair of needle nose pliers. You can grab the clip at the very bottom and simply pull straight down on it. That's the easy part. Wait till you have to try to get it back in. Once the clip is removed wiggle the sensor and pull backwards on it, it should pop right out with a little wiggling. Disconnect the wire, hook the new sensor to the wire, and push it back into the engine block.
Now the fun part. You have to put the retainer clip back where it came from to hold this sensor in. I'll fight with it for an hour and a half one night, use a lot of really bad words, and come close to throwing stuff across the yard. I finally had to walk away from it. You are really trying to put something in two small holes that is in a very tight spot, you can't see it, you can barely feel it. Ford engineers are idiots. The following morning I go back out figuring I'm going to spend a considerable amount of time trying to get the stupid clip in. Held the clip in the needle nose pliers, reached up-and-under all of the tubing and such, Felt for the end of the clip and the small holes in the block best I could, pushed up on the clip and lo and behold it snapped right in whete it belonged. Couldn't have been at it more than 20 seconds. WTF? Why couldn't it have done that the day before? Geez. Once you're satisfied the clip is in and the sensor's not going to come blowing out under pressure, start reassembling things.
This worked for my car. Seems to be a common problem for many Fusion owners. Ford should do the right thing and pay to make this right. We need a class action law suit to compel Ford to own up to their engineering short comings and stop having customers foot the bill or put a Band Aid on a bigger problem.
Again, this is intended for a 2016 Ford Fusion Titanium 2.0 turbo. May work for other vehicles but I was not working on a 2013, 2014, 2016, 2017, Fiesta, Focus, Edge, F150, Chevy Volt, or Toyota Tundra, or a multitude of other vehicles I was being told where temperature sensors were. Your results may vary. Hope you find this helpful.
