Hi all,

 

I have recently purchased a ST150 and have done a small amount of the service stuff to make sure the car will be generally okay until I finish it. For context, I have only replaced Oil and filter, Spark Plugs and Power Steering fluid. 

I have noticed that unlike my other mk6 (Style Climate) that the coolant temperature stays fairly cold. In my other car, the coolant temp stays at the middle point which I assume is good, however in the ST150, it runs at the point (or slightly below) between middle and completely cold consistently unless idling, which then goes to the middle point, and just starting the engine from cold. Can anyone inform me if this is an okay thing or if there is anything I need to replace asap.

It doesn't make any difference with performance and I have been unable to find an answer that doesn't involve a broken temperature sensor constitently reading completely cold. 

Possibly a thermostat stuck open?

I think some engines have a good old wax thermostat which opens and closes as the coolant heats the wax in the thermostat unit, and some have an electronic valve that opens and closes from ecu signals. I don’t know what this engine has.  Also some cars have the temperature gauge directly linked to a resistor type of sensor in the coolant, resistance gets less as it gets hotter, making gauge go up . WhereAs as on some cars the sensor feeds to ecu and then the ecu tells the gauge what to show. I don’t know what type this car has.

If a 70s car we would all say take thermostat out and put in a saucepan of water and heat up on cooker and watch if it behaves correctly, ideally with thermometer in saucepan. It’s all got a lot more complicated and a lot harder to get to the thermostat.