After replacing the thermostat it couldn’t hurt to replace the temperature sensor as well... what engine do you have?

Also a cracked coolant resivoir is common on this series of vehicle.

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Auto Enthusiast. Tech Extraordinaire.

05' Land Rover LR3
06' E53 X5 3.0i
07' X3 3.0si
08' X3 3.0si
17' Interceptor 3.7 AWD Sedan