D7E D339 putting combustion gas into radiator ( 47A3829 )

Had to top off radiator with 5 gallons or so after sitting over winter.

Ran machine for 15 -30 minutes. Found black sooty film in rad next morning. I believe this has been ongoing issue.

Drained coolant and pulled number 4 precup. Looked ok. Re-installed and filled rad back up and warmed up machine to find bubbles in rad when revved up.

Coolant has black sooty film again next morning.

I'm leaning towards pulling heads to see what's going on.

Any advice? Thanks

Candidate leakage causes of combustion gas in coolant can be pin holes in pre-combustion chambers, cracked head/s or block, low cylinder liners and failed head gasket. Yes, pull the heads.

As a long shot you might try retorquing the head bolts to see if that has any affect before pulling.

What does a guy rig up to bolt the liners down to check protrusion? Thanks

there is a cross bar that bolts over the cylinders then a depth guage is used to take the reading. shims are used to set the height of the liners.

liners have to be removed to change the shims and liner orings if the liner isnt at correct height

I use the head bolts with packers of some sort under them to stop the liners from lifting. If you don’t turn the motor you won’t have to hold them down. You hold them down if you turn the motor over because the pistons can lift them. 1 to 4 thou above the block deck and no more than 2 thou difference between cylinders beside each other. Hope this helps.

Why not check all 4 pre combustion chambers before pulling the head? Maybe the pre cups are not screwed into the head on this engine, on the D318 engines having the head solid on the block is as good a place as any unscrew them.