Cummins isx 15 coolant loss no external leak

I start loosing coolant on my truck after replacing the radiator. No leak but i keep loosing coolant.
Oil is clean, crankase breather is clean, transmission cooler is by passed, egr is deleted, no white smoke out of the exhaust. Where is this coolant going ? How much air can be trapped in the system if possible ? Truck is running fine no overheating

 

Update: it was the air pockets in the cooling system, i didn’t do the right procedure to get rid of the air after refilling the system, i will run it and will update soon once again to confirm it was the air and not some other issue

 

Well…
It went from max to min again. I decided to do a combustion leak test with that blue fluid from amazon, unfortunately my engine failed, color changes from blue to green meaning that is comb gases in the coolant and leading to head gasket or cylinder head issues. What are you guys thinking ? Once again, it does not puke coolant thru the reservour, no smoking no coolant in oil. Could be something else like air compressor ? I have replaced only the head on the air compressor not long ago i think i bought it on amazon, could have failed that one ?

 

I did not noticed any blake flakes to be honest but yeah this one is making normal pressure in the reservoir. I mentioned above, my dpf and egr is deleted, so my question is, is there still going coolant thru the egr cooler ? Exhaust manifold is good pin point to check but it will be more then couple hours especially if them bolts snap

 

That is my fault, i should have bought the whole unit together even reman was better.

 

Is there a way to check egr cooler for leaks or do i have to take it apart to find out ? Do you know if turbo and manifold needs to come off ?

thank you

 

If i remove this little flex pipe, will i be able to see if there is any leaks ? Also on the flex pipe from the exhaust i see some white and reddish mark.