Car temperature

JustinR1979

Retrogamer wrote: »

If the heaters still get as warm as they did when it used to hit 90oC then it's likely the CTS (coolant temperature sensor)

If the heaters are only luke warm and not as warm as they used to be at 90oC then it's likely the thermostat.

Coolant temp sender - sender for dash, sensor for ecu
Sometimes they're a dual switch.


Bora tdi will be easy, takes a few minutes, and if euros have a deal on a bottle of coolant and the stat for about a tenner.


As you say, if the heaters are getting hot I doubt it's at a genuine 45C.
Does the gauge move at all?

Stoke

Those dash readings are usually !!!!!. Get an OBD2 Scanner imo.

tberry6686

Stoke wrote: »

Those dash readings are usually !!!!!. Get an OBD2 Scanner imo.

To do what ? The OBD scanner will display the temp supplied by the sensor - giving no help in finding the problem as it would still boil down to either the sensor or thermostat.

JustinR1979

Indeed...
Feel some pipes, feel some heater heat.
Go from there.

Richard53

The thermostat lets the coolant heat up more quickly, that's all. It has no role to play in keeping the running temperature down. If the temp gauge is reading a steady 45 deg, then unless you do your driving on the Ross Ice Shelf, there is a fault with the sender or gauge.


If your coolant temp were really 45 degrees, then the thermostat would never open (most open around 85-95 deg) and your top hose and radiator would be cold, even after a run.

arcon5

Richard53 wrote: »

The thermostat lets the coolant heat up more quickly, that's all. It has no role to play in keeping the running temperature down. If the temp gauge is reading a steady 45 deg, then unless you do your driving on the Ross Ice Shelf, there is a fault with the sender or gauge.


If your coolant temp were really 45 degrees, then the thermostat would never open (most open around 85-95 deg) and your top hose and radiator would be cold, even after a run.

The thermostat merely blocks the coolants passage to the radiator. The wax construction melts as temperature rises allowing for coolant to redirect through radiator which has a thermostatic switch activating the fan when necessary.

It doesn't act as an aid to increase temperature and most certainly has a direct role in managing the coolant temp.
Stuck closed = overheating engine
Stuck open = overcooling - irrespective of the fans operation due to the ramair

Richard53

arcon5 wrote: »

The thermostat merely blocks the coolants passage to the radiator. The wax construction melts as temperature rises allowing for coolant to redirect through radiator which has a thermostatic switch activating the fan when necessary.

It doesn't act as an aid to increase temperature and most certainly has a direct role in managing the coolant temp.
Stuck closed = overheating engine
Stuck open = overcooling - irrespective of the fans operation due to the ramair

I know how a thermostat works, thanks.


I didn't say it acted as an aid to increase temperature, I said it let the coolant heat more quickly. Obviously it has a direct role in managing the coolant temperature. That's precisely what I was saying.


OP said his temp gauge was reading 45 deg. Scotsman4th suggested it might need a new thermostat. I said that the thermostat was unlikely to be the cause, as a stuck open or even missing thermostat will only delay the engine warming up, it won't prevent it reaching proper temperature eventually. OP was talking about the temp reading after a long run.

reeac

Richard53 wrote: »

I know how a thermostat works, thanks.


I didn't say it acted as an aid to increase temperature, I said it let the coolant heat more quickly. Obviously it has a direct role in managing the coolant temperdature. That's precisely what I was saying.


OP said his temp gauge was reading 45 deg. Scotsman4th suggested it might need a new thermostat. I said that the thermostat was unlikely to be the cause, as a stuck open or even missing thermostat will only delay the engine warming up, it won't prevent it reaching proper temperature eventually. OP was talking about the temp reading after a long run.

I disagree. I have an old sports car which has an ether-based temp gauge and it's dead accurate and very sensitive. When up to temp you can see fluctuations which show that the stat is continually opening and closing every few seconds. The stat maintains the correct coolant temp by varying the time open vs the time closed taking into account ambient temp and engine power output.If a defective stat is stuck open then the engine will be undercooled which will increase wear, sludge formation and fuel consumption.

AdrianC

Richard53 wrote: »

I didn't say it acted as an aid to increase temperature,

Except it does.

as a stuck open or even missing thermostat will only delay the engine warming up, it won't prevent it reaching proper temperature eventually.

It certainly will, especially a vaguely modern diesel at low ambients. The radiator will be shedding more than enough heat for the coolant temperature to quite simply never reach normal temperature or - if it does, in heavy traffic - it'll drop again very rapidly once there's more than nominal airflow over the rad.

It's also worth remembering that modern temp gauges aren't really temp gauges in the way they used to be. They're ECU controlled, and basically just display "Cool", "Normal", "Hot" - the needle won't move from the centralised "Normal" position across a relatively wide range of temperatures within the normal range, whereas an older gauge actually displaying what the sender is telling it will give you much more detail.

Stoke

tberry6686 wrote: »

To do what ? The OBD scanner will display the temp supplied by the sensor - giving no help in finding the problem as it would still boil down to either the sensor or thermostat.

No, not necessarily. Volkswagen's for example are known for having dash temperature readings that seem to bear no resemblance to the actual ECU. An OBD2 Scanner will give you a truly accurate reading, then.... go from there.