Discovery Sport 2016, temperature gauge is slow to rise and when going down hill will fall to nearly the blue band, I have taken it into the Land Rover garage and they have fitted a new sensor cost about £100 and £720 to fit it as they had to dismantle the front of the car to get at it. It is fairly obvious to me that cooling water is leaking into the radiator all the time hence slow to warm up with an out door temp of 19 C and cools down when the engine is on over run going down hill. My question is, what does the sensor do other than tell the engine management what temp the engine is running at and inject more fuel when the engine is below normal running temp. Does the sensor open and close the thermostat valve or is the valve independent of the engine management ? Have I got a faulty thermostat which is nothing to do with the sensor ? When I took it back the day after fitting the sensor they made adjustments to the engine management which needless to say has not cured the problem at all. I will be pleased to know if any one else is familiar with a faulty thermostat.

 

It is possible that the variable water pump is the problem and it was a a minor problem in early Diesel engines.

 

Hi Canuk,
Problem was easy to solve, the thermostat wouldn't close properly ie. coolant was leaking into the radiator before the engine reached operating temp. easy to check put my hand on the hose going to the radiator, it should have been cold (engine cold, running for 5 mins) but was warm, that confirms coolant is leaking past thermostat when the thermostat should be closed. Solution, simple, fit new thermostat, as I intend keeping the disco for many years I asked them to fit the plastic housing with the new thermostat (being plastic eventually it will crack) Cost, housing & thermostat £100 & £700 to fit, expensive, as the front of the disco has to come off and the radiator to get to the thermostat.