I've got a 2023 X 110 with 15K miles. I had a battery fault -- since I don't drive it often enough, so I took it to the dealer. The dealer did a warrant replacement on the battery and then did a courtesy fluid, tires, brakes check.
The next morning I left on a trip. One hour into the trip, while driving up a pass on a busy Southern California freeway the vehicle gave me a big red critical overheat warning and said something like "Critical Overheating -- Engine Shutdown". The Engine didn't actually shut down, but it went into some type of limp mode. We were in the fast lane of a five lane freeway and were able to get to the shoulder. On the way to the shoulder (turned off the radio) we could hear boiling or air gaps in the heater core in the dash -- very loud. On the shoulder, it was clear what the issue was. The coolant reservoir cap was missing and coolant was all over the engine and side of the vehicle.
We were not in a safe place, but we waited about 20-30 minutes for it to cool down, filled it with a bunch of Desani water, zip tied a plastic "cap", and drove it a few miles to the next exit and were fortunate to have an auto parts store at the bottom of the exit. The auto parts store was able to get an OEM cap delivered in a couple hours. We let it cool two hours and then filled with new coolant (and kept topping off) and we were able to get back home.
At home, I verified (home cameras) that when I brought the car home from the dealer my driveway was clean and when I pulled it out from my driveway I had a puddle of coolant. So, the dealer clearly forgot to put the cap back on after the fluid check.
I returned it to the dealer the next day. They were super apologetic and owned up to the mistake. They vacuum flushed the coolant system and pressure tested it. They also tested the block and did a chemical test on the oil and didn't detect any coolant in the oil. They also steam cleaned the engine and detailed the vehicle.
I asked them to pull the fault data to see what the peak temperature was, but they said the JLR MCU does not store fault codes or temp for overheat events -- that seems crazy, since it records so much other data.
Does anyone have experience with an overheat event? When the vehicle goes into limp mode due to overheat is it still at a "safe" temperature range or a dangerous/destructive range? Any other suggestions on things to check or document?

 

I am glad you were safe and that the dealer owned up their mistake.
I had an experience with Defenders overheating during a Land Rover Experience event in Namibia. Super high outside temperatures of 130 F.,.and the Defenders were running hard in low range on rough terrain. We would stop and pour gallons of water over the engine, and the warning signs disappears. The heat sensor gets hot and triggers the warning, hence the pouring of the water over the area of the engine where the sensor is located. Those engines are though. We were in diesel engine Defenders.
I suspect your incident had a lot to do with the coolant reservoir cap missing.

 

I definitely get why you’re asking this question. Long term damage possibility. Or not. Any chance you noticed the temp gauge on the dash when this was happening? Pegged at the red?

(Like, with old Discovery 2’s, one significant overheat and the engine is warped, cooked, or head gaskets gone and need replacement - if not immediately, very soon thereafter in my experience, every single time)

 

I can confirm that the ECU will not store data like a flight data recorder by design. It may have a fault that set and the data at the moment of fault will be stored. Like a snapshot.
Typically there is a balance of a failure/mistake that happened, the consiquntial damage caused by the failure/mistake, and what the driver does when the failure happens. The good news is that the vehicle gave a major warning telling the driver there is something wrong and /or telling them that the vehicle will shut down or serious damage may happen. That is better than the days of the past where there was hardly a warning and the driver could continue driving without noticing there is an issue which can cause more serious damage. The vehicle even cuts back engine power to protect itself to try and protect itself.

It seems like the service center took responsibility for the mistake that happened with the expansion tank cap not being secured. They did their due diligence in filling/bleeding the cooling system. Pressure testing the cooling system and performing what seems to be a combustion gas analysis in the cooling system. Then cleaned the engine bay. If more damage occurred while driving it with the active failure, it would show up on the tests or you will see symptoms of the consiquntial damage very soon. Exhaust sweet smell, excessive pressure in cooling system causing more coolant loss and overheating, coolant consumption, or oil/coolant mixing.
I would suggest to drive it normally and check the coolant level periodically. Maybe swing by the service center periodically and let them inspect the vehicle to make sure all is well. These engines are pretty resilient to overheating, but not immune.

 

Would it be worth asking the Dealer for an extended warranty? At least cover the engine for future possible coolant related issues? Just a thought...

 

Unfortunately I did not see the temp gauge or at least remember where it was, that is why I was hoping the ECU recorded it. I did see the big dashboard alert and the engine noticeably lost power, but not all the way (some type of limp mode?) after it said it was shutting down. I thought I would have to coast my way over to the right shoulder, but the vehicle still had power. I have driven a few hundred miles since and everything seems OK, but I am more concerned with the potential for long-term damage. The dealer really was great about the situation. I feel good about the tests they ran.

It still surprises me I was able to drive an hour without the coolant cap on, since it is pressurized -- and was noticeably leaking in my driveway before I left. I am disappointed in the temp indicator on the vehicle. It seems to me they have made the digital indicator way too "friendly" -- always sitting dead center until it isn't and then the engine is overheating. I'll take an old analog gauge over that any day of the week. I just don't know how resilient the P400 is from overheating... Is it like the wcc's in Namibia (happens all the time no big deal) or is it like the old Disco 2's where it's one and done?

Thanks for the insights.

 

A note: I believe it is completely normal that you could drive for awhile with an unpressurized cooling system, then all of a sudden have what is essentially a boil over. The coolant reached a point where it boiled, and then is all over the place.

Some context: Lots of people, for example, on old Discovery 2’s actually keep their coolant caps unscrewed (but attached) full time so that the system does not pressurize - the thought on that platform, is that with a healthy cooling system, and a modified from stock (lower) 180 degree or aftermarket thermostat, that the system will in most use cases operate at a low enough temperature that pressurization is not needed. There is a lot of discussion about this over the years on D2 forums and it’s what alot of enthusiasts do to minimize the high strung D2 motor head gasket issue. The though tis that your coolant will boil over and you’ll see it and stop long before your head gaskets will blow (see a parallel?)

Obviously the L663 is a much different design of a system -- but fundamentally, it makes sense why you drove for an hour, then on an uphill pass which would naturally raise cooling system temps via load on the engine, you’d get a severe boiling incident with the system unpressurized.

One note: Dash gauges "even out" the temperature. They aren’t displaying the exact temperature because it concerns customers when it moves up and down like temp gauges used to do, so JLR has a range where when it’s within that range, it stays dead center. Which inspires confidence in the driver/customer. But in actuality -- as you drive, and conditions change - uphill, downhill, engine load and speed -- there can be LARGE swings in that temperature on a normal modern vehicle. So say 184 to 220 or slightly higher would be very common on coolant temperatures in a pressurized modern cooling system.

One more point. Temperature targets in modern cars like L663 is not the same all the time. For emissions and performance reasons, the Defender has both “requested coolant temperature” and an “actual coolant temperature” data in the system. The car, based on parameters, requests a temperature from the various valves and variable ELECTRONIC thermostats on the car, and they try to deliver that temperature. When there’s a huge mismatch (car requests 195, car can only achieve 220) -- something’s up or the loads / ambient temp / stress is very high. I was in Moab last year on VERY hot days offorading, and I created a screen in my GapTool to watch these temps, it was very interesting to see it all moving around. Notably, I’ve coded in Dynamic mode on my 110, and when you switch to Dynamic mode, it requests and tries to achieve a sub 200 degree (F) temp in the car. To leave some headway for performance and increased engine loads that may be expected in dynamic mode. Problem is, you can’t use dynamic mode in any offroad conditions. *** Interesting tidbit -- the air suspension compressor temperature has similar data available in Gaptool and it’s great fun to predict when you’ll get a suspension error by watching it heat up through use, big obstacles, etc.

Hope that makes some sense.

 

@nashvegas this is good insight. Thanks. Interesting that the ECU calls for different temperatures in different driving modes. That makes sense. Also interesting that the compressor communicates its temperature. I would image there are TCUs all over that are transmitting on the bus.

 

If the cooling system passed compression testing, and if they did a cylinder compression test (unclear from your initial post) AND checked the existing coolant for hydrocarbons and all came back ok then I think you're good.

When it comes down to it, despite modern efficiency and performance requirements seemingly make everything break - modern metallurgy and material science has given us some pretty resilient engines.