Engine coolant level in surge tank ?

[Rizop]

looks like my coolant level is low again after 5 months . When the dealer looked at it in February , they mentioned that sometimes the factory underfills it , and they didn’t see anything out of the norm . They added a little coolant just short of the seam but it’s been steadily decreasing in the past 5 months .

I removed the plastic shroud over the radiator to see if I could find any type of residue but the radiator looks good .

The manual mentions that if you have to add coolant more than four times in A year ,to visit the dealer, so I’m wondering if some loss is normal or why else would it state that . There seems to be some debate online of whether the system is completely closed or not , or if there is evaporation . Does any one else have any experiences with slowly declining levels ? Thanks everyone !

 

[StephenPT]

2020 LM2...Where is the coolant going?

www.gm-trucks.com

Some other owners of LM2s commenting on coolant usage. I don't know that this is necessarily an LM2 issue, but there's a ton of coolant hoses on these rigs for EGR cooler, oil cooler, fuel cooler, etc. etc. I'd suggest poking your head around in the engine bay, crawl underneath it and inspect with a really bright light. If there's a coolant leak that is a pin-hole leak from a hose, you might not necessarily see the red coolant on the hose, but coolant that evaporates always leaves behind a chalky residue. See if you notice that on any of the coolant hoses.

Also, I'd keep track of how much and how often you add coolant to the reservoir. Take pictures and build a "story" if you do need to take it to the dealer and show them your documentation. It's going somewhere - just need to figure out where. To rule out a head gasket issue, you could take an oil sample and send it off to Blackstone Labs or a similar oil tester. They will be able to see coolant in the engine oil.

 

[steiny93]

These systems do not use coolant by design, the coolant isn't evaporating.

But... these baby diesels (dmax & ecoDiesel in particular) struggle with consumption due to leaks within the numerous fittings necessary for them to operate.

My last ecoDiesel consumed a lot of coolant before they found the issue (EGR); it took a couple years of back and forth before we got it figured out.

 

[Rizop]

These systems do not use coolant by design, the coolant isn't evaporating.

But... these baby diesels (dmax & ecoDiesel in particular) struggle with consumption due to leaks within the numerous fittings necessary for them to operate.

My last ecoDiesel consumed a lot of coolant before they found the issue (EGR); it took a couple years of back and forth before we got it figured out.

Thanks so much StephenPT and Steiny93 for your insightful comments . Huge help about the possibilities and how these systems are designed . Sounds like there may be a hose or fitting loose . Will try to get under the car as well with a bright light to inspect myself

I’ve sent the vehicle in to the dealer before for this issue . Worse case scenario is that I’m still spinning wheels on this and they can’t find anything . Is there a way that I could put dye into the system myself in an attempt to track the leak and assist thr dealer ? I’m a pretty big noob aside from changing my oil and changing the fuel filter , so this is kind of my first rodeo

 

[StephenPT]

Thanks so much StephenPT and Steiny93 for your insightful comments . Huge help about the possibilities and how these systems are designed . Sounds like there may be a hose or fitting loose . Will try to get under the car as well with a bright light to inspect myself

I’ve sent the vehicle in to the dealer before for this issue . Worse case scenario is that I’m still spinning wheels on this and they can’t find anything . Is there a way that I could put dye into the system myself in an attempt to track the leak and assist thr dealer ? I’m a pretty big noob aside from changing my oil and changing the fuel filter , so this is kind of my first rodeo

Yep - https://www.amazon.com/ACDelco-10-5046-Dex-Cool-Detection-Tracer/dp/B008I2VKNI

You'll also need a UV light.

As I mentioned, there's a considerable amount of rubber hoses to move coolant around on this rig. All the way at the back you have a couple of hoses just above the muffler moving coolant in and out of the rear aux heater core. I'd start there and work toward the front of the rig. Next to the transmission on the driver side is a fuel cooler and transmission cooler with coolant flow.

Driver's side of the block are multiple hoses for the thermostat manifold. Frontwall behind the battery on the passenger side are your coolant hoses for the main heater core and the tee-fittings to send it to the rear aux core. You also have low pressure and high pressure EGR coolant flow. Last, but not least are the connections from the water pump to the radiator and the radiator back to the engine. You don't need to examine the hoses that are part of the CAC cooler as that is an independent system that does not share coolant with the engine.

Hope that gets you started - I know the dealer should be figuring this out, but the reality is there just aren't very many dealers with qualified techs that can figure out these kind of issues that aren't solvable with a DTC and a troubleshooting tree.

 

[Rizop]

Yep - https://www.amazon.com/ACDelco-10-5046-Dex-Cool-Detection-Tracer/dp/B008I2VKNI

You'll also need a UV light.

As I mentioned, there's a considerable amount of rubber hoses to move coolant around on this rig. All the way at the back you have a couple of hoses just above the muffler moving coolant in and out of the rear aux heater core. I'd start there and work toward the front of the rig. Next to the transmission on the driver side is a fuel cooler and transmission cooler with coolant flow.

Driver's side of the block are multiple hoses for the thermostat manifold. Frontwall behind the battery on the passenger side are your coolant hoses for the main heater core and the tee-fittings to send it to the rear aux core. You also have low pressure and high pressure EGR coolant flow. Last, but not least are the connections from the water pump to the radiator and the radiator back to the engine. You don't need to examine the hoses that are part of the CAC cooler as that is an independent system that does not share coolant with the engine.

Hope that gets you started - I know the dealer should be figuring this out, but the reality is there just aren't very many dealers with qualified techs that can figure out these kind of issues that aren't solvable with a DTC and a troubleshooting tree.

Super helpful ! Yes I’ll try to do my due diligence just in case the dealer is short on qualified techs . When the dye is in the system , do you think a thirty minute drive , then parking it overnight be enough for the dye to manifest itself if there is a leak ?

 

[Stbentoak]

Super helpful ! Yes I’ll try to do my due diligence just in case the dealer is short on qualified techs . When the dye is in the system , do you think a thirty minute drive , then parking it overnight be enough for the dye to manifest itself if there is a leak ?

My leak was a transmission oil/coolant heat exchanger mounted to the side of the transmission. Looks like a solid block of aluminum with a bunch of sandwiched plates. Once replaced, my coolant has held steady.

 

[Scott in AZ]

Dealer will take care of this I’m sure , but just a reminder to always use Orange Dex Cool coolant, don’t mix with other formulations or colors. The different types of coolant all work well, but don’t mix well.

 

[Rizop]

Just a quick update : took the Yukon in to see about this issue again . I had poured dye in the coolant tank a few weeks beforehand .

The dealership pressure tested the system for a day , but couldn’t find any leak or dye residue . Basically implying that it was in normal operating specs for coolant to slowly go down over time with some of the engines . Not sure about this

 

[steiny93]

Just a quick update : took the Yukon in to see about this issue again . I had poured dye in the coolant tank a few weeks beforehand .

The dealership pressure tested the system for a day , but couldn’t find any leak or dye residue . Basically implying that it was in normal operating specs for coolant to slowly go down over time with some of the engines . Not sure about this

These systems don't consume coolant.
Totally possible that it wasn't 'full' from the factory. But once the system has stabilized you shouldn't see any coolant reduction day over day. If the level is dropping it's because it's leaking.