DD15 sounds like a train, can a valve adjustment save it? Or is it too late.

2015 Freightliner Cascadia came in sounding like a train, first thing I recommend you do is connect to the truck and check for fault codes, the fault code we found SPN 1326 FMI 31 IDLE SMOOTHNESS CONTROL/ CYLINDER NUMBER 4 QUANTITY DEFICIT AT IDLE. Next we walk around and do a visual inspection. We found a coolant leak the passenger side. Next step is start the truck, verify the complaint and do your due diligence. Check the oil pressure, check for any oil leaks, fuel leaks, coolant leaks. We then went into the a relative compression test to help verify the problem. We found ZERO COMPRESSION at cylinder 4 and low compression at cylinders 5 and 6. Performed a valve adjustment and hoped that might work but we were not successful. Still had ZERO compression at cylinder number4. Customer authorized for us to remove the cylinder head and head and found a broken valve.