Coolant missing

Well let's start with filling us in of what engine and truck it is.

 

First thing to do is a pressure test. It may show where your leak is. If it's a head gasket your oil will be milky.

 

Can you see exhaust coming out your stack? What color is it? Could be mixing in the combustion process and blowing out your exit.

 

Could be magic, possibly.....

 

Yup, pressure test with the oil pan off will show if it’s getting past the head. Or maybe it is a hose that only leaks under high pressure, which a pressure should show you.

 

there are two leaks. cold and hot. you have to break it down.

 

I had a similar issue in a T660 with the Cummins . About every other week I would have to top it off to trip the low coolant sensor , we did a leak down test without any signs of leaking out , it had to be going through the engine but it didn’t matter since at 750,000 miles it tossed a rod bolt through the side of the block

 

It's still the egr cooler.

 

Good ole isx window block. It stays cooler from the fresh air.