If anyone here has any experience chasing a coolant leak on a Duramax, I could use some advice...
I have a leak that is dripping down the oil cooler and bell housing (driver's side). It's not much, but enough that I don't feel comfortable driving it without fixing it. It is a 2015 GMC Sierra 2500 with the LML. Prior to the leak, the truck was tuned and deleted, but the EGR has been in place until I started looking for this leak. Other than a Fass lift pump, the truck is basically stock.
Chasing this leak so far I have:
-Replaced the oil cooler with a banks L5P oil cooler, brand new gaskets and o rings.
-Replaced the coolant block off plate on the bell housing (passenger side) with a PPE o ring plate.
-Removed the EGR blocking off the EGR coolant line running down the back of the engine.
-Replaced the coolant hose and fitting, typically going from the heater core to the EGR, however now going straight into the thermostat housing.
After all of this, I still have the same drip in the same spot. I cannot see any leaks around the turbo coolant lines and everything seems dry around there. It also doesn't seem to leak until I pressurize the system.
Any help would be greatly appreciated, this one is kicking my ass.
Man that sounds aggravating. Having the same truck I know what’s under the hood and sounds like you’ve touched on everything. There’s a duramax forum over on Reddit where mechanically minded and true mechanics post a good bit. These folks seem to know these motors front to rear. Chasing things like this will make you pull your hair out, I wish you all the best!
I’ll ask my pickup tech later this morning when he gets in.
Thanks for the support, gentlemen.
I put everything back together, added dye to the system, and let the truck warm up to 180*. I don't see any green (antifreeze dye) anywhere at all. Maybe I was over pressurizing the system with my tester causing it to weep.
I'm about to put the front axle back on, and drive it. Once it gets closer to 200* I'll know if I fixed it or not. There should be plenty of pressure to see a leak at that point. I should have put dye in it from day one, but I got ahead of myself.
Well, I have no idea why, but it doesn't leak now. I have not touched a single part of the cooling system since I pressure tested after replacing the oil cooler. It held 15 psi all night last night and didn't leak a drop. I've driven it approximately 20 miles and nothing. Not a drop out of the coolant system.
If you have a Duramax with a leaky oil cooler, just know it's not a fun job at all.
Thanks for the moral support!
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I’m glad it worked out for you. Is the l5p oil cooler a direct bolt on? Mines hanging in there but I’ll file this info away for future use lol
I appreciate it!
The L5P cooler will fit anything except the LMM engines, with a little help. You have to trim the exhaust manifold heat shield and cut off the boss holding it. Very easy, took me 2 minutes with a die grinder and a cutoff wheel. You can buy the Banks cooler which is ready to bolt in, or you can buy a factory 2020+ cooler and source your own gaskets and coolant elbow.
Thank you so much, that’s great to know!
It might have been coolant drippin down through the frame or some nonsense maze and seemed like a continuous leak but was just residual from the job you did.
Either way sounds like a win! Sometimes they fix themselves!
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