Hey guys- Duramax newbie here. I picked up a 2006 LLY with 190K two weeks ago that was cheap, but is undoubtedly in rough shape. On the way home- the low coolant light came on the DIC. Went to put all new filters/fluids in and noticed the oil was milky. No doubt there is coolant getting into the oil. I am having some issues with diagnosis of the location of this coolant leak. Seeking some internet help.
- Truck did have an EGR code when purchased. Put it on HP Tuners the day I bought it and disabled EGR and copied a stock LBZ tune while I was there. I would assume the EGR cooler would only send coolant into the exhaust if faulty. No white smoke or coolant smell from the exhaust, but thought I'd mention what has been done as it is pertains to coolant flow.
- No pressure in the upper radiator hose. Always nice and squishy. Otherwise I would definitely diagnose as head gasket. This is what has me looking elsewhere for the leak.
- No oil in coolant. Coolant in oil only.
- No visible coolant or oil leaks under the truck.
- Does not overheat. Never above 210 on the gauge. Usually running slightly under that.
- Truck runs flawlessly after the new fuel filter. Runs and drives real nice other than the coolant loss that has me scratching my head.
- Lost 1/2 of the coolant from the fill line in the reservoir in about 6 hours of mixed driving. Low coolant message came on roughly 5 hours in. I checked coolant after 2 hours of straight driving and it seems to have not lost any coolant. The light came on shortly after my last stop. Leaking while truck is not running maybe? Anyone heard of that?
- Is there a good way to route coolant around the oil cooler? Thought about bypassing as a diagnosis step. Don't want to throw parts at it if not necessary. I have came across a couple of people who have had issues, but looks like the pattern shows oil in coolant, not coolant in oil.
- Besides the oil cooler, head gaskets, or catastrophic failure (cracked block/head), is there anywhere else where the coolant could leak into the oil?
- Have not done compression or leakdown test on the cylinders. Obviously would be a good idea.
Any help and input is appreciated. Just trying to get the location of this internal leak diagnosed before tearing into it or throwing parts at it.
I really do love this truck already as I am a diehard GM fanboy. Bought it primarily to haul the racecar and farm equipment besides being a daily driver. My priority is to make it 100% mechanically sound and get on to fixing some other minor issues that have not been addressed. This mystery leak is now the only thing standing in my way of that. Sorry it was a long-winded post. Thanks in advance!
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- Truck did have an EGR code when purchased. Put it on HP Tuners the day I bought it and disabled EGR and copied a stock LBZ tune while I was there. I would assume the EGR cooler would only send coolant into the exhaust if faulty. No white smoke or coolant smell from the exhaust, but thought I'd mention what has been done as it is pertains to coolant flow.
- No pressure in the upper radiator hose. Always nice and squishy. Otherwise I would definitely diagnose as head gasket. This is what has me looking elsewhere for the leak.
- No oil in coolant. Coolant in oil only.
- No visible coolant or oil leaks under the truck.
- Does not overheat. Never above 210 on the gauge. Usually running slightly under that.
- Truck runs flawlessly after the new fuel filter. Runs and drives real nice other than the coolant loss that has me scratching my head.
- Lost 1/2 of the coolant from the fill line in the reservoir in about 6 hours of mixed driving. Low coolant message came on roughly 5 hours in. I checked coolant after 2 hours of straight driving and it seems to have not lost any coolant. The light came on shortly after my last stop. Leaking while truck is not running maybe? Anyone heard of that?
- Is there a good way to route coolant around the oil cooler? Thought about bypassing as a diagnosis step. Don't want to throw parts at it if not necessary. I have came across a couple of people who have had issues, but looks like the pattern shows oil in coolant, not coolant in oil.
- Besides the oil cooler, head gaskets, or catastrophic failure (cracked block/head), is there anywhere else where the coolant could leak into the oil?
- Have not done compression or leakdown test on the cylinders. Obviously would be a good idea.
Any help and input is appreciated. Just trying to get the location of this internal leak diagnosed before tearing into it or throwing parts at it.
I really do love this truck already as I am a diehard GM fanboy. Bought it primarily to haul the racecar and farm equipment besides being a daily driver. My priority is to make it 100% mechanically sound and get on to fixing some other minor issues that have not been addressed. This mystery leak is now the only thing standing in my way of that. Sorry it was a long-winded post. Thanks in advance!
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