I have a 2007 L322 TDV8 with 267K miles on it. It's running fine but takes an age to get up to temperature. Coolant level is fine, heater works fine, viscous fan appears fine. If I leave it idling the temperature gauge drops to half way between cold and normal. Under normal driving the temperature gauge sits smack in the middle as it should.

I'm thinking thermostat(s) - and here's the question - How many thermostats does it have, where are they, are they mechanical or electrical and is there an easy way to check them without stripping it down ?

Or am I barking up the wrong tree entirely ?

Many Thanks