Rollin'_Coal

So tonight I was driving and the wife noticed the heater started blowing cold. Almost immediately after she mentioned it, the mini-maxx defueled on high coolant temp at 220F. I threw it on defrost and cranked the heat up and it **** near instantly blew hot again and engine temp dropped to 190ish where it always sits. I stopped for a look and found the reservoir is full to the hot mark, seemed normal but the rad cap is cold. Cracked the lid, big puff of air from the rad, no coolant. Took about half a gallon and a few big gulps of air came out and level is just slowly going up and down in the neck (not really pulsing, more like breathing). After driving for awhile, the temp is fluctuating between 190-200 as the t-stat opens and closes, seems very normal but the rad cap is still cold. I cracked the rad again and it blew out some coolant as I would expect from a hot engine but it's still cold to the touch when the gauge is reading in the normal range. There doesn't appear to be any leaks, especially not to the tune of half a gallon but it is dark out there. Lots of heater blows very hot, belt is on pump, reservoir doesn't look like it has moved.

Any ideas where an air pocket that big may come from after 180000 km's?

Busboy

I would first check your engine oil for signs of coolant from a blown head gasket, then if you have any cardboard in front of or between the rad I would take it out and use a winter front. I would also check the strength of your coolant if too low it could be partially freezing in the rad on the hiway then causing a surge and blowing it out the overflow of the fill reservoir a sticking thermostat might cause the same surge, if the coolant is not in the oil and there are no leaks it probably went out the reservoir overflow that's why it's still full.

Rollin'_Coal

Oil looks good on the dip stick, no foam or milky liquid and I take a sample to a lab every oil change and results have never given me any reason to believe I have internal engine problems. It seems to me I would see heavy pulsing in the rad of it were a head gasket blown through to the water jacket. I will check the coolant today for a good freeze point but it was only -5 here most of the week and the truck has been running great up north closer to -40. No cardboard, factory winter front is on with the flaps open right now as it's not cold out. If it went out the reservoir overflow I would think the rad would pull liquid back in when it cooled no?

Busboy

Once air has got into the cooling system as the temp and pressure of the cooling system rises the air pocket absorbs the pressure so no coolant is forced out into the reservoir and as temp and pressure drop the air just depressurizes that's why it's wise to remove the rad cap occasionally when the engine is cold, the coolant should be right up to the top. Might want to check the weep hole on the water pump too....

EXC_Rider

Could be a problem with the rad cap. Also, check the overflow hose for cracks or holes. Both need to be in good shape for an overflow tank to work properly.

tbarbee1

When I had these symptoms it was my head gasket. $6k and ARP studs later everything was back to normal.

Cris Moldovan

What was the problem Rollin Coal? My 2014 is doing what seems to be the same thing! Thanks

Rollin'_Coal

Mine ended up being the EGR bypass hose from the delete kit had a leak where the coolant line slides into the aluminum pipe (standpipe?/head pipe??). Coolant was dripping when it was cold starting in the morning but burning off on the manifold so no trace in driveway. Found it when it got worse and started leaving puddles and ended up getting the better style clamp from glacier diesel. No more leaks. On the 13 or 14's I've heard there is a plastic fitting on the rad that cracks on a Y fitting of some sort. Mine doesn't have that but may be worth a look.

Cris Moldovan

Thanks! I'm all stock. Yes the upper rad hose had a pin hole leak in the Y. Changed it! And also replaced the water pump and new belt! Still after about 1 hr coolant light shows low. 😖 Where could it go? No signs. Fresh oil. Drives fine. 🤔🤔🤔

Busboy

I suspect it wasn't filled all the way just keep topping it up but keep an eye on that "Y" they have a poor reputation. The water pumps don't seem to last as long as they used to, my son changed his 2013 water pump at around 100k so have a look at the weep hole on the bottom of the pump.