Coolant flowing into crankcase

Morrismotosports

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Jul 23, 2014
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I just bought my first diesel yesterday a 2005 chevy 3500 4x4 4 door duramax I have been wanting a diesel for a while but did not have 10k to throw down on one so got a project. The truck has 300k miles but all it's life it ran up and down east cost delivering signs large store front signs. The company I bought truck from told me that the truck lost power on a trip and had to be towed back it was taken to mechanic and was told it needed head gaskets because water was getting in oil understandable so I bought it. I got truck home and drained oil out and it did have coolant in oil so I thought I would fill coolant system up and let it set over night just to see if had to be under pressure to leak into crank case. I started to add water ( I still had oil plug out ) I added about half a gallon of water to empty coolant system and immediately started to flow clear water out oil drain plug hole I know at that time it could not be the heads because there was not enough water added to fill up to heads and only seeing it making it has high as water pump is it possible that the water pump is leaking into crankcase maybe cracked or something has anyone ever seen this before thank
 

LBZ

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Jul 2, 2007
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Moved here.
Definitely possible to be leaking past the water pump but usually you get a leak out the weep hole in the water pump as well.
Could also be a cracked water jacket leaking into a cylinder.
You may want to do a compression test seeing as it lost power to rule out a cracked cylinder or head.
 

durallymax

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Apr 26, 2008
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I agree its possible. C12s and some others are known to push a pile of coolant into the crankcase if the weep hole gets plugged when the pump goes out. Seen some dump a gallon a day in. The driver will notice oil level went up a gallon and coolant went down a gallon lol.

Have you ran it at all? is it burning coolant?

Trying to think about how things are plumbed, if a bad oil cooler could leak like that just from filling it up.
 

LBZ

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.............

Have you ran it at all? is it burning coolant?

Trying to think about how things are plumbed, if a bad oil cooler could leak like that just from filling it up.

It could but if you ran it you would get a lot of oil in the coolant as well. Oil pressure is higher than coolant pressure. Without running it this is stuff to say as the leak point.
 

durallymax

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I do see signs of oil in coolant the jug is stained black. I am going to pull water pump tomorrow and check it

The stains can be from combustion gases. Generally are actuall, the oil will just leave a residue but not stain it IME. Some are stained for other reasons or from previous issues as well.
 

Morrismotosports

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Jul 23, 2014
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So today I pulled oil cooler and blocked coolant passages from water pump to oil cooler and from oil cooler to engine block and still leaking into crankcase
 

Tjsdmax

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Jul 4, 2010
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I am pretty sure there is a frost plug behind front cover ..that could be a spot to check I had one do the same thing frost plug was not seated correctly ....its got to be a big hole to take water that fast and come out oil pan plug ....I think u can see the frost plug from the water pump hole ...