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Case 1840 with Cummins 4-390 - Lots of coolant in oil, but zero oil in coolant

Shoe3669

Member
Joined
Jul 30, 2023
Messages
24
Location
KC
Well I lost about 6 quarts of coolant into the oil system in a matter of 5-10 minutes of running, but I don't have any trace of oil in my coolant. I have removed the oil cooler and am going to pressure test it, and I also removed one of the valve covers and noticed some traces of coolant there. Would this indicate a potential head gasket failure? What are some common things that I should test based on having coolant in the oil but not the other way around? Thanks!
 

Delmer

Senior Member
Joined
Jan 3, 2013
Messages
8,923
Location
WI
If it happened that quickly and running the whole time, then oil pressure being higher than coolant pressure, it shouldn't be the oil cooler. Could be the head gasket with that much coolant it would spread around. But don't take my word for it, pressure test the cooling system and see if you can find the leak, might have to take the oil pan off, but this is a sleeveless engine, so if the coolant has ever been replaced, it's not as likely to be a cylinder issue, more likely a head or head gasket, right?

I don't know the specifics of that oil cooler housing, if there's a gasket in there that would allow coolant to the crankcase.
 

alrman

Senior Member
Joined
Jun 20, 2009
Messages
3,316
Location
QLD Australia
Occupation
Diesel Fitter;Small Business Owner;Cleaner
There are a couple of welsh/expansion/casting/freeze plugs located behind the engine side cover. It's well worth checking those before you get too carried away pulling the head etc.
They are supposed to be stainless, but that doesn't mean that they are.... item #8

4-390 welch plug.png
 
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