When I got my 2016 back at the end of last October, the pink coolant in the main degas bottle was just visible in the clear top half of the bottle. By the time 5k miles rolled around, the coolant was no longer visible in the clear section. At oil change time, the dealer "topped" it, resulting in it being visible in the tank again. 3k miles later, the coolant has disappeared below the clear part of the bottle again. What gives? The secondary bottle level has not budged. Its clearly not losing a lot, but it is definitely going down slightly.

 

And I assume it isn't spraying out the top? (Only reason I ask, is that I got the dealer to top off my main coolant system degas bottle because when it cooled down, it was below the clear plastic part of the bottle, which they argued was OK. Of course I pointed out, then why does the bottle have a line indicated the lowest acceptable 'cold' range on it? Anyhow, they topped it off a little and when the truck got up to operating in Miami temps, it promptly blew it out the top of the bottle. You could see the spray pattern on the underside of the hood and the level went back to where it was. If I checked the level immediately after a long drive or sitting in the heat in traffic the coolant level was 'high'...

Even up here my 2015 sits a little low and once again Asked the tech about it, because I thought it was a little lower than it should be. (and lower than my 2011 was). And he said, it was perfect and to leave it alone... I still check it and WISH that the entire bottle was clear.

So you may have a problem or not, my guess if it is really leaking or being burned up somewhere, the bottle will go dry.

 

Its not blowing out anywhere, I'm kind of fanatical about cleaning under the hood, so I would notice.

I never asked the tech at the oil change to top it off, either, so they apparently felt it was too low. Yeah, I wish more of the bottle was clear as well. I guess, just watch it.

 

I went through this with my last 2015. Even sent oil to be tested and dealer checked ear cooler too. Bottom line is air was trapped in the large hose coming off of radiator. Go and shake it, if you hear sloshing its still not full and coolant will go down till all air is purged from it. There is no bleed point for it so all air has to circulate through.

 

About the only way is to do a pressure test of system. Let dealer do it as warranty covers it. It could be a lot of things.

 

I like the idea of the air bubbles; have not heard of this happening before though. I can ask the dealer, but won't be before a couple of thousand more miles.

 

Couldn't you bleed it by running the truck with the coolant over flow cap off?

 

I don't think so, the system is a closed system other than the degas and I don't think the cap will bleed it out.But I didn't try it, so I don't know. When my coolant kept slowly dropping I was looking everywhere for coolant I would squeeze the top hose and could hear the coolant slosh back and forth. When the sloshing stopped, the coolant stopped dropping. That was 35k miles ago. The air from this hose and top of radiator is the highest part and if not purged properly it takes a long time for it to bleed out. I think ford does have a special way to purge this air out, and op might look into it. mine did it naturally but took time. There should be zero sloshing when shaking the upper hose.

 

After a few, I slosh around myself and it takes awhile for things to clear up...

Sounds plausible, reasonable, and easy to check. Glad you are not spewing coolant out...

Now to figure out where it is going.

 

Sometimes I loose a little coolant. I just top it off. I have probably added about a quart since the truck was new.

Used to add a little in my 6.4 as well.

No leaks. Even the turbo fitting is nice and dry. No loss at the cap either.

I think because of the heat you just loose some once in awhile. At least I do.

Been over a year since I added any though.

 

The only other time I lost any coolant with one of my super duty's is when my 2012 developed a small radiator leak at 35k miles. Other than that and this 2015 that apparently left the factory with an air bubble I have never used a drop of coolant. By 8000 miles my radiator tube filled up and the degas hasn't moved off the hot and cold marks we put on the side of the tank with a marker and that was 33k miles ago. I don't think these engines should loose coolant, but there is so many places it can.

 

I'll try sloshing it in the hose later. I don't smell coolant anywhere, and there is nothing leaking under the truck. Its a pretty small amount overall that it has dropped, but it is dropping.

 

The only thing that worries me in that you should continue the exercise in finding out where it is going, is that a head gasket could be leaking... In that case you would be burning up the coolant in the exhaust after treatment plant before it leave the tailpipe. Especially if it is a slow leak.

I haven't heard of too many blown head gaskets with this motor though - if you had a 6.ohh I would be much more worried...

On Edit: Have you thought about using dye? Of course make sure that dye is OK to use in these beasts.

 

Yeah, I thought about head gasket too, but I kind of doubt it. We will continue to monitor.

 

Like I said, I haven't heard of many head gasket failures, so I am leaning towards that not being the case...

I'm interested if you ever figure it out as to what it is.

Kinda why I was thinking dye wouldn't be a bad idea if it was compatible with our coolant. Using a black light, it would stick out like a sore thumb.