Symptoms
Coolant dropping from max to min within 100–150 km with no obvious puddle.
The fix, step by step
- Pressure-test the system, then check the turbo coolant feed and return lines (their O-rings are a known leak), the expansion tank and its level sensor, and the auxiliary radiators behind the front intakes for stone damage.
- Replace the leaking lines with new seals and refill and bleed.
Tools & part numbers
- Cooling-system pressure tester, sockets
- turbo coolant lines and O-rings, coolant to spec
Where to buy the parts
LR128288 auxiliary radiator, New Defender 2.0/3.0LR Direct ↗Amazon ↗
Defender 2020 turbo coolant pipe (search)Rovers North ↗
Hunting a used or discontinued part? Search eBay Motors for Land Rover Defender (L663) parts →
Rated for a competent home mechanic with a decent tool kit. Confirm torque figures, fluids and procedures against the factory service manual for your VIN, support the truck on stands rather than a jack, and work at your own risk (disclaimer). Some parts links are affiliate links, which pay us a small commission at no cost to you.