Symptoms
Unexplained coolant loss, sweet smell, weeping at the back of the engine or around the thermostat housing. Plastic pipes typically go around 100,000 km and water pumps around 80,000–140,000 km.
The fix, step by step
- Drain the coolant and remove the supercharger to reach the valley.
- Replace the factory plastic rear crossover pipe, front Y-tube, oil-cooler-to-water-pump adapter and front crossover bypass with aluminium parts.
- Do the water pump and thermostat housing while it's apart.
- Refit the supercharger with new gaskets, then refill and bleed the system.
- The supplier recommends professional installation.
Tools & part numbers
- Full socket set and torque wrench
- coolant and drain pan
- ARC050 kit (LR122709/LR109402 rear crossover, LR092992 Y-tube, LR028136 adapter, LR090630 bypass) or SCV85LAUCK kit with water pump and aluminium thermostat housing
Where to buy the parts
L405 5.0 water pump (search)Atlantic British ↗
Hunting a used or discontinued part? Search eBay Motors for Land Rover Range Rover L405 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.