New LLY Duramax owner with coolant leak

[sticknrudder]

Hi, my name is Chris. I have owned a couple of 7.3L Powerstrokes over the years, after that I've had a couple of gas GM trucks. I've always liked GM trucks better, so I was excited to be able to purchase my first Duramax a couple of weeks ago. I flew from MI to San Antonio to pick it up, and it is truly a TX truck with no rust. 304,000 miles and it drives like a new one. About halfway into the drive home, I realized it was losing coolant. It appears to be coming from the back of the engine on the passenger side and leaking down the frame. It's not coming out of the breather tube. I'm hoping you guys can help me track it down. Should I post this here or should I post it in the LLY forum? Thanks

 

[TheBac]

Moved to LLY section.

Its either a heater hose, turbo coolant hose or the small plate on the transmission adapter.

Sent from my SM-G986U using Tapatalk

 

[sticknrudder]

Thank you! I liked the fact I heard nothing about head gaskets

 

[TheBac]

Well, those three are the easy things to check. If it isn't one of them, you know what to look at next.

 

[ZeroGravity58]

Check the upper hose after it sits all night. If it's rock hard in the morning it's more then likely the head gaskets. With that kind of miles if they haven't been done your not far off.

 

[sticknrudder]

Check the upper hose after it sits all night. If it's rock hard in the morning it's more then likely the head gaskets. With that kind of miles if they haven't been done your not far off.

This is the hose you're referring to, correct? If so, it doesn't seem hard at all. Last I drove it was more than 24 hours ago.

 

[TheBac]

Yes. If you can squeeze the hose, thats a good thing.

 

[sticknrudder]

Yes. If you can squeeze the hose, thats a good thing.

Yes I can easily squeeze it completely flat. I just need to figure out how to check for those other three things you mentioned. It’s pretty tight back there by the firewall.

 

[moparkxracer]

Like he said start at the highest one ( heater core fittings) and see where the leak starts from.. you can also get a flash light and look down to the top of the engine block to see if the valley is filling with coolant as well. There is a drain hole on the back side of the block that lets fluid from valley drain. That drain hole lets the fluid flow past the small cover mentioned on the engine adaptor plate. I’d recommend getting a pressure test kit from local auto parts to help save some headaches on finding the leak.

 

[Chevy1925]

pressure test it for sure. there are many little coolant hoses for the turbo and some intermediate ones for the heater core as well that can leak like you are stating.

btw, head gasket is not out of the picture yet. if the HG are original on that truck, they can leak to the external of the engine and never have a pressure building problem like a typical head gasket. Start with the easy stuff though

 

[zakkb787]

pressure test it for sure. there are many little coolant hoses for the turbo and some intermediate ones for the heater core as well that can leak like you are stating.

btw, head gasket is not out of the picture yet. if the HG are original on that truck, they can leak to the external of the engine and never have a pressure building problem like a typical head gasket. Start with the easy stuff though

This ^^^ definitely check your little things first. My 2006 (lbz with LLY head gaskets blah blah) developed a coolant using/leak and I couldn’t find it. Hose wasn’t hard. Kept driving it for months and noticed coolant everywhere one day. From behind the oil cooler. Pulled the cooler thinking that was the culprit and the HG was blown out the rear of the head. This won’t make your upper hose hard because the water is going outside the block instead of mixing into the coolant system.

 

[ZeroGravity58]

Pull the pass side inner fender. Get it hot and look at the back of the motor and see if you can see where the coolant is coming from. I'm putting head gaskets in my lbz now because of this. The gasket was blows between the #7 cyl and the Coolant passage and also from the coolant passage to the external part of the head. It would build pressure when I drove then after is sat for a few hours it would dump a whole puddle of antifreeze out of the back of the pass side head.

 

[sticknrudder]

Ok thanks for the info everyone. Is this the type of kit I’m looking for?

https://www.amazon.com/YUAN-Automotive-Cooling-Radiator-Pressure/dp/B078G28GGM/ref=mp_s_a_1_3?dchild=1&keywords=coolant+pressure+test+kit&qid=1621345150&sr=8-3

 

[NevadaLLY]

did you figure this out? The valley of the block can catch all sorts of leaks and they flow down the back of the block. The turbo hoses are my bet, especially the feed that goes from PASS front to turbo. It makes a 90deg turn with a small 3/8 rubber hose with spring clamps. If you remove your intake, it should be right under the mouthpiece to the turbo. If not that one, check the hose that goes from the thermostat housing to the top of the radiator (driver side). There's a fitting for the turbo feed pointed toward the firewall. That would be my next check.

 

[NevadaLLY]

did you figure this out? The valley of the block can catch all sorts of leaks and they flow down the back of the block. The turbo hoses are my bet, especially the feed that goes from PASS front to turbo. It makes a 90deg turn with a small 3/8 rubber hose with spring clamps. If you remove your intake, it should be right under the mouthpiece to the turbo. If not that one, check the hose that goes from the thermostat housing to the top of the radiator (driver side). There's a fitting for the turbo feed pointed toward the firewall. That would be my next check.

as you can see, mine leaked after my new build

 

[sticknrudder]

I did figure it out! Thank you for all the ideas. Turns out it was the plastic connector between the egr cooler and the heater core. Easy cheap fix. Rented a coolant pressure set from Autozone and made it easy to find