MTU 8v183 losing coolant

Hi.
Looking for any help on this subject. After a 7hr cruise my port motor lost 1 1/2 gallons of coolant in the wall mounted coolant reservoir tank. A year ago I had a similar problem and it was the exmanifold. I replaced one manifold and the problem stoped.
I removed the inspection plates on the exmanifolds and there is no signs of water intrusion. The oil looks clean with no signs of water. If I had a blown head gasket or a cracked head would I see signs of coolant in the oil or in the ex-manifold.
Thanks for any help
Bryan

Two things.
Last trip was 6hr run and everything was normal in the morning when we left, coolant level was good and oil looked fine.
Pulled into port around 9pm that evening and did not go into the engine room that night.
Next day went into the engine room to do checks and saw coolant in the bilge, about a gallon or so. Cleaned up the bilge and put down fresh pads.
Topped off the coolant tank with just over a gallon of coolant and started the 7 hr leg of the trip with the cap of the reservoir tank half turned so pressure was not building in the system.
Keep a very close eye on the coolant tank and the engine room for any signs of coolant in the bilge, the tank dropped would drop about 1 inch a hr. But no coolant in the bilge.
We are at this dock until Monday than need to make the 8hr run home.
Just trying to test what we can with limited equipment on board.
Thanks for the help.

Update
Found that the coolant lines that go from the turbo and intercooler to the wall mounted coolant tank where completely plugged.
Unclogged lines and filled and filled the tank and now see good circulation in the tank.
Could this have caused so much pressure that it could have blew coolant out of the coolant tank and into the plastic over flow tank with so much pressure that the coolant just went straight through the recovery tank and straight into the bilge
3 hrs into the leg home and engine temps are normal and no coolant in the bilge.

Lines