MK6 2Ltr TDDI fan running but cool engine

[tricksum]

Fan running flat out but engine cool,temp gauge normal.Went into limp mode.
Started engine immediately and drove normally,temp gauge rapidly rising to max but engine feeling cool.Engine pulling as normal.
So managed to get home with repeated episodes of temp gauge going up and back to normal and into limp mode.
Coolant reservoir level normal through out.No pressure when releasing cap.Radiator just a little warm.
Temp sensor,thermostat or air lock?or something else maybe.
Your thoughts would be appreciated.

[Burn2]

Hello.

You need to take a look of the real temp.

Could be a sensor problem, a water pump that does not a make a lot of flow.
A bad pressure cap could bring some problem too but perhaps not like that.
Normally after a travel you should have pressure in the cooling system.
Thermostat is possible too.

That's why you need to get real temp with forscan to see if temp move fast or not and what happen in idle.

[Frag]

The water pump on the 2.0 fwd mk6 is driven from a spline into rear of PAS pump,they are prone to corroding then losing drive to water pump.


CHT sensors do also fail on this model,
I’d probably run it from cold while feeling at the pipes to determine what actually happening temperature wise.

[knobby1]

That's why you need to get real temp with forscan to see if temp move fast or not and what happen in idle.

How would Forscan do this..?? There is no actual temp sensor other than the CHT....it uses the CHT to extrapolate what it thinks is the actual coolant temp.

Lord Knobrot (Smithy)

[Burn2]

If the temp given by the cht sensor jump ( or better to see the reported voltage ), you should normally know that the sensor is wrong and need to be replaced.

i said real temp, not calculated temp from over sensor.

[knobby1]

If the temp given by the cht sensor jump ( or better to see the reported voltage ), you should normally know that the sensor is wrong and need to be replaced.

i said real temp, not calculated temp from over sensor.

The CHT sensors do indeed fail sometimes...and if it does....how does Forscan know what the "real" temp is..??

Lord Knobrot (Smithy)