Engine Temperature issue

[danA6]

Hi all,

I've noticed a small issue with my 2l tdi where in city driving my engine will warm up to 90 deg c and usually stay there but once im on a motorway it will drop to 70 deg c and hover around there. Engine runs like normal with no issues, new water pump + cambelt kit 4000 miles ago. Not had a chance to change the oil yet. I've got my own theories but thought I would pop the question out there and see if anyone has a clue as to whats going on. 

Cheers

Dan

[Magnet]

Suspect thermostat Dan. 
Regards

 Gareth. 

[danA6]

1 minute ago, Magnet said:

Suspect thermostat Dan. 
Regards

 Gareth. 

Okay. Do you think it would be simple as to chuck a new one in to fix it?

[Magnet]

Please share your own theories with us Dan. 

[danA6]

1 minute ago, Magnet said:

Please share your own theories with us Dan. 

My thought was its the thermostat too. Maybe being stuck open slightly which then allows the coolant to run around the engine constantly. At city driving speeds the airflow is minimal so it allows engine to get up to temp. With more airflow at 70mph the radiator reduces the temp in the coolant allowing it to drop to 70 deg c. I think the thermostat still fully opens as I don't run hotter than 90c so may just need a clean or a couple coolant flushes to take away any possible gunk that's keeping it open. Though ive heard that there are 2 thermostats on these cars but I'm not sure I've got them. 

[Magnet]

Thanks Dan, 

You could be right that there are indeed two thermostats. Worth checking LLL Parts website? 
‘…. as simple as chuck a new one in to fix it..’ 

If you are asking me to guarantee that replacing the thermostat would fix the problem, then the answer is No. Like every other forum we can only make sensible suggestions. 
Regards,

Gareth. 

[danA6]

8 minutes ago, Magnet said:

Thanks Dan, 

You could be right that there are indeed two thermostats. Worth checking LLL Parts website? 
‘…. as simple as chuck a new one in to fix it..’ 

If you are asking me to guarantee that replacing the thermostat would fix the problem, then the answer is No. Like every other forum we can only make sensible suggestions. 
Regards,

Gareth. 

Thank you for the suggestion Gareth. I’ll have a look at the part website.

I understand that now, thank you for your help. 
 

Dan