My Defender had massive coolant loss with no obvious reason. JLR pressure tested and found no leak, there was no external evidence of coolant, no loss of power, no white smoke etc.... It just seemed to be disappearing. Was going through approximately 1l every 100 miles or so, more when driving at higher revs. Car could sit ticking over for an hour on my driveway though, and coolant level wouldn't drop.
JLR insisted on replacing the expansion tank cap first of all, then the tank itself, with no improvement. Ran dye through the system but came up with nothing. Basically washed their hands of it.
Took it to an independent Land Rover garage who found the fault to be an internal leak in the charge air cooler. Coolant was escaping at high revs, burning off and going out the exhaust when driving, but despite the amount of coolant lost the smoke from the exhaust was not noticeable.
New charge air cooler fitted, problem solved.
Just wanted to inform others what worked for me. Hadn't seen it mentioned anywhere else before, so may be worth investigating if you have similar problems.
The garage said they were able to identify the problem by pressurising that component only, as they had experienced this problem before.

Hope this helps someone else along the way!

 

No leaks on our 2021 but 2 slow leaks on our 2023. One at the intercooler and another where the lower radiator hose meets the engine block.

I've owned a lot of different vehicles over the years and none of them ever had a coolant leak until now. Funny how the Defender brought back a problem that I thought was extinct.

 

Thanks for sharing your experience. I had a tiny leak on my 2023 Defender that the dealer could not find, and finally they discovered it was coming from the water pump.

 

Slow leak no smell or coolant on the ground. Found during service visit for a recall to be the o ring and hose for turbo. Dealer replaced parts and all seems good now.

 

My less than year old Defender had a low coolant warning earlier this year. The dealership covered it under warranty.