odd issue with my 2019 Discovery 5 TD6 today. vehicle has 144,000 kms on it and it was 6 Celsius today. after driving for 15 minutes a Red warning appeared on the dash- STOP SAFELY ENGINE OVER HEATING. The temperature gauge was in the red zone. i stopped and shut off the engine for about 5-8 minutes. i started the engine the temperature had dropped to about normal. After driving for 10 minutes same routine- overheated stopped again. i decided to head home and figure out what was going on. i had to stop 2 more times before reaching my home.

The engine has no visible coolant leaks and the coolant level was not down at all. i connected my scanner and there was no engine codes. 30 minutes later i drove the Discovery for 40 minutes and the water temperature rose to its normal position and no more over heating. has anyone had a similar problem with the TD6 Land Rover?

 

Sounds like you need a new thermostat. Most likely it is stuck closed.

 

I wouldn't suspect a thermostat to be stuck closed intermittently, but not impossible, TD6 water pumps are in some way electronically controlled. Maybe that could be something? I'd suspect cooling fan(s) but if you're driving and it still overheats maybe not. If you have the software/tools, I'd monitor live coolant temps for a while to see where it's really at. I've seen coolant temp over 230f in mine pulling my 7500lb travel trailer up a long grade, but the vehicle temp gauge read dead center. In the ambient temps you're driving under regular load I'd expect temps right around 200F ish. Diesels have 2 coolant circuits both with their own sensors. The auxiliary system if not in use is typically 20-30f over OAT. At least from my experience.

 

gmfain- agree thermostat would seem a likely culprit. unfortunately the vehicle seems to run fine again today with no overheating. temperature continues to run right on normal. might just get a spare thermostat to have on hand... perhaps a temperature sensor as well.

 

Update. I’ve now had my third day of driving with absolutely no indication of overheating. I have a come across two different instances of this identical problem on Defenders. It’s the exact same problem temperature gauge in the red zone and large red overheating warning on the dashboard but no evidence of the engine actually overheating. One is on the Defender forum- it was a 2024 Defender. The other was a long term review of the 2021 Defender by Motortrend magazine. They had the exact same overheating warning. In both cases the Defender was dropped at the dealer with this reported problem, and they were unable to duplicate it. I realize the Defenders have gas engines, but the problem was exactly the same as my Discovery. Indicated overheating when the vehicle hadn’t overheated, and the incident didn’t repeat itself. In both cases the Defender owners thought a software update cured the problem.

 

its now over a month and 4,000 kms later and never a repeat of this overheating indication. no coolant leaks and have never had to add coolant.