Originally Posted by limeport
Thermostat and Fan Clutch were recently replaced by very experienced LR / RR mechanic who has worked on my RR, LR4 and Defender for several years. Temperature gauge is acting the same way it did before and after replacement of thermostat and FC.
I expect you'll be getting full refund for the pointless work done on your truck then.
At idle the engine shouldn't need the fan to regulate its temp ... Unless you are in a desert. The standard radiator setup should be more than adequate. The thermostats job is to restrict the cooling and keep the engine warm!
If you can't cool enough at idle the fan is just masking the problem.
You need 2 things.
A good radiator ... They tend to silt up at the bottom. Check the temp is even ish from top to bottom. If it's cool at the bottom it means it's silted up. Back flush, new core or new rad time.
A pressurized system. The system needs to be under pressure to cool efficiently. Do you hoss get firm when the engine is up to temp? If the don't check the radiator cap first. There was a bad batch going around once upon a time. It's also worth putting a pressure tester on while you are at it.
Or you could just ask your very experienced mechanic because he surely did all this before swapping out the parts he did.