Hi guys...

Been a long while since I've posted. I am just shy of 90k and the truck has been great. Only thing it has needed was a set of new plugs around 40k and new brakes and rotors for all 4 corners around 75k.

But, now I have an issue. I have searched and googled for over 2hrs this morning and decided it was time to throw in the towel and ask.

Truck is a 2012 F150 S-Crew, Lariat, 4x4, 5.0L, 66" bed.

Backstory:
The other day I noticed I had no heat at idle (intersections/stoplights) I checked the coolant level and she was down almost a gallon from proper cold fill. The day after, I got the sweet coolant smell, saw a few small puffs of steam, popped the hood and saw the coolant reservoir full with it puking the excess out the vent.

Since this began, I do not recall hearing the cooling fan run.

Am I right to assume it is either the fan itself or the relay controlling it?

Is this a common problem? Anyone else with this issue? Anyone know the fix?

Thanks

 

It's easy enough to see if the fan is running when the engine is getting hot. What does the temperature gauge read during this time? It could be a sticking thermostat. It could also be a blown head gasket.

Check the fan to see if it runs when needed. if it does check the coolant for hydocarbons. If no hydrocarbons are present, change the thermostat.

You need to fix this ASAP or you will end up with a blown head gasket.

 

Temp gauge on the dash never moves beyond normal.

Correct me if I am wrong, but if the thermostat was sticking, it would not be puking hot coolant out the coolant reservoir vent right?

 

It absolutely would. Some of the coolant bypasses the thermostat Over 15 psig pressure is what is pushing the coolant out of the reservoir. This can be caused by the coolant temp getting high enough to overpressurize the system or a head gasket is leaking causing compression pressure to be leaked into the cooling system If the temp gauge is reading normal when this happens, there is some air void in the system keeping the gauge sensor from reading true temperature or the head gasket is leaking. Beginning to sound more like a head gasket leaking. Start the checks.

 

Thanks for the reply but, Yuck.

I was hoping to find a simple fix on here. I'll swap a thermostat but it is too cold for me to do anything serious. (nor do I have the desire) If that does not fix it, then it is going to the local shop.

I sincerely hope it is not a HG, but if it is, looks like the fix is a trade-in and I'll be driving a 2018 F-350 sooner than later.

 

You can test your thermostat by putting it in a pot of hot, boiling water.

It will also clean it.

You'll see if it works or not.

If the thermostat opens, this confirms the thermostat is able to open.

 

Roadie, thanks for setting me straight.

Manual, thanks for getting me off my butt to go and check out the t-stat.

I pulled it, and if it is not "the" problem, it is at least "a" problem. I did not even throw it in a pot of water as I could already see that the rubber seal was mostly separated and just hanging there. I picked up a replacement, ill fill with water and see if it cures it. if so, ill drain and refill with a fresh mix of 50-50.

 

Sounds like you are on the right track.

I had a similar issue on a Honda Accord where the thermostat was the cause of the engine loosing coolant. Not the same as your issue, however, as the coolant heated up, it would vent off as you drive through that cap/seal. Since coolant is 50/50 water, a lot of it turned to steam and left the cooling system, which made it appear as if the engine was using coolant. Wound up the rubber seal was just shot. Replaced the coolant and t-stat cap, problem solved.

A head gasket issue would also indicate white smoke or exhaust fumes that smells like coolant, excessively dirty coolant with an oil haze on top, coolant that smells of oil and gas, over-pressurized system (by then your coolant would have oil and/or gas mixed in).

Some might say, the cooling system is a "closed" system -- it is, but not like A/C type of "closed" system. Some still escapes to the atmosphere. It is a 98% closed system. That is why you are supposed to check it at regular intervals and top off as necessary.

 

I usually keep a pretty good eye on it... admittedly since the white stuff started falling on the ground, I have not pulled the hood to look. The symptoms happened quick though. Heat one day, none the next. topped off water, had heat again for a day and then it went away again... I saw steam out the hood, popped it and saw it purging fluid.

Truck is not beat on nor abused, so I'd think it unlikely that the HG was going... though completely possible.


Replaced t-stat, topped it off, and took it for a ride. Fluid is holding steady, nothing strange going on, heat works, etc. All seems to be well. We have a few days of mild weather so ill let it go tomorrow and make sure it behaves... then do a complete fluid change (which it needs anyways)

 

Sounds like you got it fixed.

When you flush the system, keep a bottle of coolant handy in the truck for about a week. Just keep an eye on it. Sometimes there are crevices air likes to hide and it takes a couple drive cycles to get it evened out.

 

I'm calling it fixed. Still no issues or hiccups. Just got done draining it, flushing it, and refilling it. Refilled with enough straight coolant to make a 50/50 mix. Hopefully she is good for another 5yrs.

Thanks again guys.

 

Congratulations!

 

l have the same exact symptoms in the same exact truck. However there is a very small presence of oil in the water overfow, but not in the crankcase. The truck runs smoothly, until it starts getting hot. Brother I'm scratching my head to