Polo GTI, weird oil temp readings over 150C is it sensor issue or real?

[Dedman]

Hi Folks,
I’ve got some issues with a 2014 Polo GTI - it had a hard life with It’s boy racer owner before i got my hands on it last year, and I’ve been steadily nursing it back to health.


Right now it’s behaving very strangely - the oil level sensor appears to be broken, and the console displays “oil sensor: workshop” - that should be enough for me to bring it to the dealer… but I put the diagnostic tool on it to see what was going on.
And mostly, the oil sensor was reading zero… and the other oil level sensors were reading ok.
I checked the oil level and it was fine, so I decided to hold off a bit before getting into the dealer.
I kept the diagnosis tool hooked up.. and started to notice some strange behaviour. After about 30 mins driving, once everything warmed up, the oils temp would go crazy high, moving from a steady 90C, up to 140-170 - at which point the oil level sensor would start reporting a reading.


Now, when it happened I’d stop driving immediately - and it would mostly return back to 90C and no oil level reading.
Occasionally I wouldn’t be able to pull over, and it would magically return to 90C… and the oil level sensor would continue to read a value until the next ignition cycle.


Once when pulled over I checked the oil


I checked the oil level with the dipstick and it was showing empty! So I topped it up with a couple of litres.. next time I started the motor and checked the oil it was reading overfilled. So I was thinking maybe there’s a blockage or a faulty pump.


So I did an oil change, thinking the oil would be toast after getting that hot… but it was fine, clean, no sludge or filings, no unusual smells. Took the opportunity to check the oil level sensor too, it didn’t appear to have any blockages, heat damage or anything wrong with it or the connectors.


I put the cleaned oil level sensor back in and filled the car with fresh oil and everything continued as it had before.. with the oil temp spiking after ~30 mins and the oil level sensor starting yo give a reading.


I was able to get the weird behaviour with the car parked in the driveway after a short drive, kept the engine running and checked under the hood - the motor appeared fine, even though reported oil temp was 170C… I’d expect oil to be leaking out every orifice at that temp.


I had a long drive that I couldn’t avoid, so I recorded the sensors for the trip… the symptoms returned and recovered 3 times over a 2 hour trip.


So, apart from clearly needing to take it to a mechanic- I’m now not sure if I have an actual blockage in the oil system, a faulty pump, a sensor that’s corrupted other sensor readings…


I have a replacement oil level sensor which I’m considering swapping with an oil change next week… but not sure if it makes sense…


Any suggestions on what i can check to further diagnose the fault?

[MIG]

Are you sure the level sensor is where the temperature reading comes from? Disconnect the plug from it and see if you still get a reading.

Also, how is the coolant temp during these high readings?

[Dedman]

Are you sure the level sensor is where the temperature reading comes from? Disconnect the plug from it and see if you still get a reading.

Also, how is the coolant temp during these high readings?

Good question, im pretty sure the temp reading comes from somewhere else, but I was thinking maybe the level sensor is pulling the voltage of one of the other sensors up/down and causing a strange reading. But I like your idea to disconnect the level sensor and see if the problem still occurs… I’ll try that as soon as it cools down outside enough to get under the car!

also, the engine coolant stays steady at 87-90C on the diagnostic tool. (I did take a look to see if engine cooling was also playing up)

cheers for the suggestion- D

[Dedman]

So I disconnected the oil level sensor and tool the car out for a 30 minute drive.. and the oil temp hit normal running temp at ~90C after 5 mins and stayed steady for the remainder.
I’m pretty certain now it’s the oil level sensor disrupting the other sensors. I’ve got a big 2hr drive coming up, I’ll leave the sensor disconnected and see if it still working as expected. If yes, then I’ll drop the oil and change the level sensor out for the replacement one!

thanks for the good idea- I’ll post again after I’ve confirmed what I’m doing next.