Hi. Thanks for using JA! I will try and help you out.
If you are getting some bubbling in the coolant tank and you are getting coolant in the oil, I would suspect your engine has a blown head gasket. I have seen this before. Air in the cooling system and coolant in the oil kinda go hand in hand with a blown head gasket. Sorry. I wish I had better news.
Any time I get coolant in the oil, I drop the oil pan and pressurize the cooling system. If there is coolant getting into the oil , you should be able to see it.
Please let me know if you need more help or have more questions.
The only other things that can cause your problem are a problem with a cylinder liner or a cracked head. Odds are it's not one of these. I have seen the head gasket cause this on C12 engines several times.
The liners in the C12 are very durable and I cannot recall the last time I seen a failure of a cylinder liner. They hold up pretty good. It is possible the head could be cracked. If you remove the head and the head gasket looks good, I would send the head off to have it checked for cracks.
It's not common for these heads to crack but it does happen from time to time. If it is cracked, I would have no problem using a reman head. A new head will cost you twice what a reman cost.
Dropping the pan is not hard. The oil pan has a reusable gasket.
Pulling the head is not a difficult job. There is not any special tools needed to remove and install the head.
If the head gasket is leaking, you will see coolant running down the drivers side of the engine near the push tubes. If you see coolant leaking down from there, You could remove the valve covers and get a better look at it from the top.
If the coolant is coming from the front gear train, that is sign that your water pump is putting coolant into the oil.
It is recommended to replace the head bolts on a C12. Everything else can be reused.
A shop normally charges about 30 hours to do this repair. They also charge about 115 per hour. So you can see the labor would be around 3200. If you have not done a C12 repair before, it may be wise to let a shop do it. I would at least get an estimate from them.
I agree. But this is the average time that I see guys do this job in. If there is a well experience tech, he should be able to get it done in about 20 to 22 hours.