Driving along the motorway yesterday,  50mph zone,   saw the temp gauge fall down from usual 12oclock postion,  down to 1/4 mark.

 

About half a mile on,  the temp gauge started to climb back up again to the normal postion (12oclock).

 

I quickly turned on my andriod app (connected to the OBD2 port),  and it showed the temp to be at 75c  (which seems to be the normal reading once upto temp I see all the time on this app).

 

 

So I'm thinking either dodgy coolant sensor,   or maybe a sticky thermostat.

 

I notice this car's temp gauge often drops down a few degrees off the 12oclock postion if it's a bit cold outside (more evident in winter time),   but it kinda still happens in the current weather we have been having too.    Often a hard long acceleration run up a hill will bring up the temp gauge.

I used to think it's a 'feature' of diesel engines to not run as hot as petrol engines,  but now I'm starting to wonder if something is broken?

 

 

I'm having the cambelt and waterpump done on monday.

 

wondering if it's worth getting the thermostat done too?   

 

Anyone replaced one themselves care to let me know where and how it's done?

my guess would be a faulty CTS. 75C is too low for normal operation. see

http://www.briskoda.net/forums/topic/246750-the-coolant-temp-gauge-a-question-by-sheer-curiosity/

Yeah replaced my coolant temperature sensor last weekend

 

'warmed up' quicker and never fluctuated

 

And solved a revv on startup problem  

I changed my thermostat today, and it fixed the problem.

 

 

According to the OBD port data (TORQUE APP on my andriod phone),

 

the car was previously reading 75-80c normal operating temp,  and it would always drop back down to 72c (or lower) if I got caught behind slow traffic,   or was just driving economically.

 

 

Now after changing the thermostat,  the real time temp is now sitting at 89-91c, no matter what type of driving.