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NASA_ISS_Tiger
LSU Fan
Huntsville, Al via Sulphur, LA
Member since Sep 2005
7460 posts

2019 Duramax Low Coolant indication
Anyone with a Duramax have this issue? My truck has less than 20K miles on it and after I took it to the dealership to get the block heater replacement cord recall done, I started getting the "Low Coolant" indication on my driver message panel. Temps are fine, I added some one time (very little...probably a quart of water). Then I got another one the other day.

I read that sometimes there is an air pocket in the system and it finally burps it way out....causing a drop in the coolant level, but I'm curious on that one. Also this happened after I started using my heater real heavy, so I thought it could have been (a) a leaking heater core, but there's no water/antifreeze on the carpet or smell of antifreeze when I turn on the defroster or (b) the heater core had the air bubble in it.

If anyone has any experience with this, I'd appreciate it. It's under warranty..I just hate having to take the time to go to the dealership.


DownshiftAndFloorIt
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re: 2019 Duramax Low Coolant indication
Going to sound like a dumb question but it isn't spelled out here, it is full of coolant, right?

The sensor should be in the lower portion of the "burp" tank. I cant imagine how it would get a bubble there. Check if it is a resistive style sensor (metal prongs) or a float-style. If it is float style it might be sticking. If it is resistive style, the sensor may have built up gunk on it, the coolant chemistry could be off, or the sensor could be bad (should be different fault code for bad sensor).



NASA_ISS_Tiger
LSU Fan
Huntsville, Al via Sulphur, LA
Member since Sep 2005
7460 posts

re: 2019 Duramax Low Coolant indication
It's as full as the factory would have filled it. The only time it's been opened by me was to add that little bit...less than a quart, if that.


DownshiftAndFloorIt
US Space Force Fan
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re: 2019 Duramax Low Coolant indication
Then you need to open it and check. It is probably actually low on coolant.

Buy premixed coolant per the owners manual (call the dealer and have them give you a couple gallons for your trouble) and top it off to the cold line, and check again in a few days. If the dealership had to pull the block heater than they had to drop the coolant. When you do that and refill, the engine will work out the air bubbles as it runs and the expansion tank level will drop. They probably did not test run the truck long enough to open the thermostats, so it didn't "burp" till you drove it.

Eta: or whatever caused it to get low the first time has caught up again and the timing was coincidental. You should find where it is going.
This post was edited on 1/13 at 11:09 am


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NASA_ISS_Tiger
LSU Fan
Huntsville, Al via Sulphur, LA
Member since Sep 2005
7460 posts

re: 2019 Duramax Low Coolant indication
Yeah, that's what I'm trying to find out too...what was the procedure to change out the block heater cord. Did they actually remove the heater element at the block or was it a simple cut or electrical plug only with no mechanical connections broken in/with the block.

I just added 32oz of premix DexCool antifreeze and I let the thermostat open and I didn't see a drop in the level...but I'll wait a few days to make my final decision that it's ok.

I'm just worried that it's a leak somewhere internal...that would tick me off....the truck literally has 16,392 miles on it.


DownshiftAndFloorIt
US Space Force Fan
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Member since Jan 2011
56835 posts
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re: 2019 Duramax Low Coolant indication
Thats a bunch of coolant, definitely low.

If it is losing coolant internally that is a serious problem. Keep an eye on it. If you suspect it is, bring it back. Thats a serious internal engine issue.

Eta: odds are though, its just burping air.
This post was edited on 1/13 at 5:53 pm


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splastiko
Member since Sep 2009
787 posts

re: 2019 Duramax Low Coolant indication
I've got a 19 L5P with 40K miles, mine has been doing this for about 5k miles. I've read on various L5P groups/forums that it is a bad tank sensor.

The sensor is located within the tank, so the entire tank must be replaced. Apparently this is a common issue as multiple people in these groups are discussing it.


NASA_ISS_Tiger
LSU Fan
Huntsville, Al via Sulphur, LA
Member since Sep 2005
7460 posts

re: 2019 Duramax Low Coolant indication
Thanks for the input. I had seen that too but I didn't know how widespread it was. Mine was indeed low but I'm not seeing any leakage external to the truck so either it's
1. A leaky heater core that's sealed REALLY well in the cab (unlikely).
2. Leaking water jacket in the engine (I hope to God not).
3. Burping air from somewhere in the coolant system. (Hopefully this).


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