Perhaps evaporation? I know the bmw b58 inline 6 suffers from coolant consumption as well and that motor is very reliable despite that. The ingenium engines are still nascent...

 

Those cheap Goodman and Amana HVAC units are known for having low quality evap coils that leak. Any AC tech will tell you the material was too thin, brittle, or they used an alloy that was more prone to corrosion to cut costs.

Could it just be bad coils?

 

it's AUX coolers most likely. I think also as they are on demand, it looks they cant be pressure tested at the same time as main system.
But it should be a way...

 

My driver's side AUX radiator failed under a pressure test and was just replaced under warranty. I have a 2020 P300 D110S with 45k miles -- warranty expires at 50K.

Enjoy !!

 

Update, I have put 200 plus miles on the new driver's side aux rad, no leaks or smells. I can tell it was active during my driving because it was warm to the touch like the main rad. My dealer was able to activate the aux coolant pump during the pressure testing and no issues.

 

My P400 has a mysterious leak too…

passes pressure tests and empties the reservoir.

I’ve been checking the level about every two weeks since 1/31 (my last fill up) and the level just dropped from full within these last two weeks.

the last 2 weeks have had weather into the high 80s. But I also took it on a 6hr drive to hoisin and back.

makes me think it’s the aux radiators also. I’m going to bring this up with my SA.

 

I'm glad I found this thread...as I thought I was wrong about what I was experiencing. I had a very similar experience with my 2022 Defender 110 S...driving for a while, after parking I would smell hot coolant. Then, I began noticing the reservoir level going down periodically and needing to be topped off. Not normal in a 2 year old vehicle.

I took it to the dealer and they did a pressure test and found no issues. So, I took it back and kept driving. Same symptoms persisted. Then I noticed one day in the cold of winter that there was actually steam/vapor coming up from under the driver's side headlight area. Sure enough, you can look back in there and see part of the auxiliary radiator. However, I could not see a leak and there was nothing ever on the ground.

Then I found this post. Kind of baffling about the pressure test not finding this...but, I understand your explanation. So, I took the first post from this thread and a video of the steam coming up by the headlight back to the dealer to explain the theory. After they did a visual inspection of the auxiliary radiator, sure enough it is leaking.

Now they are just waiting on all the parts to replace it. It's a new part number...which make me think there is an issue with the original part.

 

I’ve been smelling coolant since my Defender was new and it was alway worse when it was hot out. Coolant level never really drops so I just assumed it was normal because I’ve looked for a leak but never found anything. Now I know where I’ll be looking next.

 

I have been smelling coolant since it was new. Glad I spotted this thread as I was going to start investigating. Had to fill the reservoir up twice, so still minmal loss. But any loss is not good and the smell was unsettling. I have 39k miles now and will take it in before warranty is up.

Any idea how to test aux radiators with pressure tester then? Do you need a computer to open a valve?

My mother-in-law has a Disco sport with P300 and I have to top her off at least once a year but I don't think she has the aux radiators.

 

I have 2023 110 p300 and it just started with this occasional "low coolant" warning. I filled it up once about 10 days ago and it lit up again today. Armed with this thread, I am taking it in for service - 36,000 miles so room on the warranty.