Hello everyone

 

I have a Mk1 Octavia estate VRS 1.8T, all is well apart from one thing which I am putting down to either a faulty Stat or a faulty coolent temp sensor, serviced the car up yesterday with genuine parts and oils while I was running the engine flush in the car and getting it up to temp after about 15 mins of ticking over at idle with the car up to temp I think it was half way, the guage dropped to cold, I ignored it and carried on doing my service.

later on I restarted the car one I completed the service and it was working registering fine again mmm odd I thought, took it for a spin around later last night and was registering fine for 15 mins again the dropped to cold again, then about 5 mins later it registered the temp again.

 

same on todays outing no signs of any overheating in the bay all seems well accept the fans are going intermittently when the cars warming not Hot?

 

I think its a temp sensor but before I replace both the Stat and the Sensor wanted a second heads up and the engine runs lovely and no jerking or anything  , thought have I possibly some how caused an air lock but then I never touched the water side just a normal service. air filter, plugs, oil and filter you get the drill. 

 

I have had similar issues on cars before with temp sensors but normally registers a fault code this isn't and keeps dropping off through out my journey its quite annoying, only had it since Wednesday its having the timing belt done next Thursday along with the water pump as im not confident doing it on this engine I don't know enough about them, but I will happily change the Stat and Sensor.

 

any advice welcomed thanks.

Sounds similar to mine which was showing same symptoms as yours .I replaced mine with cheap 6 quid rubbish from eBay i have now bought a genuine one all OK now.I should have known better however mine threw a cel on dash I don't know if its just the ECU side triggers it or the output to temp gauge as well ,when I had it scanned I think it said sensor or thermostat so its a process of elimination .is the sensor a green one ? I'm on my second replacement in 5 yrs 04 plate 89k.

Had mine replaced with OEM and mine still jumps from 60 - 90, speaking to a few others some has said they had all checks done on the car and couldn't find any issue! Seems a common issue, as mine does go up to 90 but wont stay there for long.

Once warmed up it should sit dead on 90 all the time if all is well

Temperature fluctuation like that is normally down to a failing thermostat, in good condition, gauge should stay nailed at 90 once warm.

Yeah sticky stat I'd say. All vag cars I've owned have never flinched off 90 until somethings going wrong. You'd think it would be overheating but sticking stats also cause over cooling, you'll probably find mpg drops as the car will run rich.