C15 Acert coolant issue

You need to do a bubble test. Only takes about 20mins.
If the head is blown you need to find out why it blew.
2007 has VVA's if they are not working properly, the engine builds to much pressure which can blow the head gasket.

Also is it throwing any codes. Or losing power?

 

When you rev it with the cap off is it coming out the rad?
Any codes? 9-2 9-3 9-4 9-5. IVA codes? Does it feel like the engine is losing power?

 

What @superhauler said.

I had a pre cooler spring a leak and it would cough and sputter and pour white smoke. As soon as you open the pre cooler up, it will have white residue or be wet inside.

Superhauler, speaking of pre coolers, you sold me the one that i replaced my bad one with! Still running like a champ 5 or 6 years later btw! Thank you!

 

Lonecrow2016 did you find out what happened?? I have the same issue.!

 

Replace both thermostats. If they are not letting coolant through it will boil the water in the block and cause steam and once it hits resivor the steam makes pressure me blows antifreeze out. Also check air compressor. Bad air compressor will put air into coolant system.

 

pre cooler
pneumatic heater circuit valves
air compressor
head gasket.
cracked liner flange
cracked head (usually see other symptoms first before this will cause your symptom)

they're the possible causes. top 3 are easy to eliminate which may or may not leave the cause as the head gasket.

if its blown the head gasket and has clear marks where the combustion gas has passed the fire ring then it will be from a sunken liner. late model cats don't fail head gaskets unless the load is taken off the fire ring. this happens from sunken liners. despite what the protrusion measures up like, pull the liners and measure the flange surface on the deck. you'll find a section, be it only 1 corner, has material gone and is lower than the rest of the deck. to fix this you need to cut counter bores.

I cant stress that enough. I have seen so many head gaskets replaces for this issue without cutting counter bores because the protrusion was "within spec" they're all back with the same issue within 6 months