Coolant loss no extenal leaks

It’s going somewhere if not into oil out the stack which is better in my opinion but harder to find you never said what engine and what year truck seems to be a lot of knowledgable people on this site if it’s not on the ground or in oil must out stack but you should have some white smoke I would think you know it’s a long shot but a friend of mine had a transmission cooler running antifreeze thru it never heard of that before but it was leaking into trans on an 05 Pete cat eng have no idea how common that is replaced cooler w regular type

 

I'm having the same issue, only I have an 18 cascadia, with a dd15.
Only thing different, is that I see froth on top of the coolant in the coolant reservoir... leads me to think head gasket. Granted, I have warranty, but I'd like to have an idea so I'll know how long it'll be in the shop..

 

Like Little cat says, could be your EGR cooler. And that is kind hard to test without take egr pipe of and pressure test the cooling system.. Could also be injector sleeves. all of those take some diagnostic.

 

I think he figured it out this post is almost 2.5 years old.

 

I have a 2017 FL. I bought it august 2020. I never had to add coolant and had no issues. I took it in the Freightliner for oil change, transmission fluid change and got a coolant flush. First run after doing this, I get low coolant sensor on the way back. Called them and they said it may have been an air lock.

second run after
No issues

Third run now and I’m having to add about a gallon a day. Called where I got it done and they said they can’t diagnose over the phone. So I’m going to be in Saginaw on Friday and going to FL there.

No visible leaks. Oil is black as can be. Only thing I can think of is out the exhaust. But googling for help is like googling symptoms on yourself. I’m pretty sure my truck has cancer now.

 

I know this is an old thread but my DD16 has starting eating coolant. About a gallon and a half every 4-5 days.
*Oil looks good, not milky on stick or lid.
*No froth in coolant reservoir
*Checked EGR cooler tube hot side and cold side and dry as a bone.
*No smoke from exhaust
*No power loss No codes Engine runs great.
Any ideas of what else I can do before I schedule an appointment at the dealer to check head??

 

pressurize cooling system and check for external leaks they have some lines from air compressor and fuel filter housing that like to leak.

 

I’ve checked everywhere and no sign of leaks.
How do I pressurize system is it an adapter that goes on reservoir cap??

 

Yea there is an adapter with a hand pump just like a car tester. There is another way but be careful. You can put a little bit of shop air in coolant overflow but be very careful cuz u can break radiator if you put to much. Also check make sure no coolant in fuel tanks drain a little out the bottom. They do like to mess up cup o rings

 

Auto parts store will loan you the test kit, pump it up, to whatever? 10-15lbs maybe. See if it holds pressure. Then start Truck, see if it builds pressure. A bad head of gasket should build air very quickly. Could have a pin hole in a liner, towards the top, and it’s getting burned, going up the stacks. Could guess all day long. Make sure it’s not going into the transmission, if it’s equipped with a coolant type cooler. Easy to tell, if coolant lines are running to it, or not.