LML Leaking coolant internally

Jonne · Oct 31, 2021

I have bad coolant leak wich I think is internal. I get lots of white smoke out of exhaust but it occurs only time to time. Add coolant light comes on about every 200 miles.
I really dont think its cylinder head related because i get normal pressure in top radiator hose in every situation and there is zero coolant in oil and none of oil in coolant.
I have also done pressure test to coolant system, but got nothing out of it. Pressure just escapes somewhere it cant be heard or seen.
Recently I did rerouting for egr cooler lines since I have blocked and disabled it anyways, but it seems still leaking.
Im thinking maybe turbo cooling next? Is there anything how to investigate it before I just start to look new turbo for it?
I have also read some rare occurance of cracked blocks on duramaxes, but should it have similiar symptoms as cracked head? exess pressure in cooling system and mixed oil etc...

Jonne · Nov 6, 2021

Update: Smoking/hazing seems to happen only when im coasting or idling, not so much when accelerating

roachwe · Nov 7, 2021

I would remove glow plugs and perform a coolant pressure test. Mine did the same thing. As long as I driving with foot on throttle down the interstate no issue. As soon as I let off throttle it would push water out the overflow passage side fender and water light would come on. Happen driving back for AZ to NC.

SheeB · Nov 7, 2021

I would agree with the above and do a pressure test. Remove each glow plug, and using a bore scope of some sort look into each cylinder and look for coolant. If any to be seen, head gaskets are due for replacement.

Jonne · Nov 13, 2021

So it seems that it is head gasket.
One of the glow plugs was straight up wet and tasted sweet.
Not sure if it is the gasket or head itself but i guess i have only one way to go and pull the head out.

marineswarm1 · Jul 29, 2025

LML Leaking coolant internally

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