@GavinC testing for exhaust gas in the coolant is easier than an oil sample. I think the dealer covered my test but that was a few years ago and my memory isn't great. DIY kits are only $30 or $40 and they usually come with enough fluid to test a few times.

I'm pretty sure they can really get crazy and add a UV dye to the coolant. They run it and then use a blacklight to check for leaks.

Like you said, an engine shouldn't go through coolant.

 

Insider, I would like to pick your brain again. Today, I received a low coolant warning on my dash. I opened the hood and my coolant is sitting below the min line. The Defender has been mint and no issues of it running hot. There is no puddles underneath it and I wrote the date on the max line which was 3/17/2022 and almost two months later I am below. Does it sound like the coolant is making its way into the engine? I have called LR to book an appointment to see if they can find it but I will be doing my best to find it before I go into the shop.

 

Same issue- slow coolant leak somewhere but no signs of a leak.
The dealer replaced a hose but the coolant level still drops - just at a slower rate. Adding coolant every ~1500 miles.
I’ll have the dealer check again at the next service.

 

There is a little one way gasket in the coolant reservoir I think. I saw a post where a Defender in Australia lost all the coolant through this when it failed. It's the little black plastic thing well above the max fill line. Perhaps if the coolant is sloshing about it's triggering a minute leak over time from this.

I know the system is closed and when hot, pressurized so it's very possible, probable really, that this idea is complete horse-hockey. No evidence of any leak from the reservoir.

I've had the dealer pop a small splash of coolant in mine twice now. No sign of a leak anywhere. No drips on garage floor, no wetness anywhere to be seen.

Level never dropped below the minimum mark. Was that way when I picked it up brand spanking new. Figured it was a low fill from factory and the system had burped during whatever tests they do.

Added a splash of coolant to bring it to max.

Repeated a couple of months later. It's still at the max now.

In essence , system remains leak free and pressurized but loses some coolant through this (safety?) feature. Excessive driving angles when off road may be expediting the very slow process. That's my stupid theory.

 

If that much is going thru the cap area, I would suspect that you would see the fluid residue. None of these vehicles are really more than 2 years old and even the most honorable of the Off-Road Houligans likely doesn't have that bad of an engine bay. So, I suspect it would be seen. If we were putting together a pool, I'd put my money on @_Allegedly 's experience. This is very likely a very minor leak that the pressure test is missing. Until someone mentioned the UV-light/dye, I had never thought/known that. If that's an option, that is exactly the diagnostic test I would do next. Since I suspect it is an external leak, see if they can put something in the coolant. Drive it for a while and then run the UV light. Heck, get your own UV flashlight. They aren't that uncommon. The kids had them when young and would light up scorpions in the rocks. 21st century version of putting frogs in their pockets, I guess.

 

Not sure this is helpful:
I also had the coolant light on and off over the last few months with levels slightly low. Then after parking in my garage after an hourish highway drive, a few hours later I noticed a drip under the drivers side headlight, fluid was running down the backside of and dripping off the lower valance/air dam. So, level was only very slightly low and I scheduled a service appt. They were booked a week out so I continued driving, checking the levels in the mornings but oddly, never saw the leak again. Anyway, to wrap up, there was a small split in the seam of the aux radiator. Always great to hear you are the first time anyone has seen this issue and it took a few days to get a new radiator. No issues since, no drips, no sensor alerts.

 

I would expect that your leak stopped once the coolant level was below the spilt in the radiator.

 

"All bleeding eventually stops..." (Sorry, I worked with ambulances for too long and some of the humor during training was a bit out there...)

 

Try telling that to people holding Rivian stock.

 

I am experiencing the same thing, about every 1500 miles need to top it off. Called LR and they can get me in on 6/29 at the earliest. They told me to stop by and they will top it off and by the time I drop it off I will be low and they will fix it. Sounds like they already know what the problem might be as the person was pretty much like we will get it done.
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