Help with Coolant Temperature Sensor Error

[RaffyS3]

Hi, so I have S3 8V 2015 Saloon.

Recently I had the common dreadful Thermostat housing leak, in which I've had the thermostat and water pump replaced at the same time.

After the replacement, I've noticed that my temperature gauge is really erratic, so the car warms up on idle, sometimes normally and sometimes very slow. I've noticed while driving over 20mph the temperature stops rising and starts to drop, sometimes a little or dramatically.

The heaters work fine and I don't feel the thermostat is at fault as its just been changed with the water pump.

I've got an obd reader and have come up with the codes P0116 Coolant Temp sensor 1 Range/Performance.

I went ahead and replaced the coolant sensor which I was told was on the coolant pipe just next to the radiator, which I went ahead and changed, yet the problem is still there.

I can hear the fans kick in and that is when the temperature starts to drop, sometimes slow but sometimes dramatically.

It only ever reaches normal temp when stationary for a while or else it just keeps dropping. Bear in mind it never overheats or go over, it just runs cold but never at optimal temperature unless stationary.

I now have been told there is 2 coolant sensors on these engines and 1 is on the engine block. I have managed to locate this and ordered the part but just waiitng for delivery.

I hope this sorts the issue out.

Has anyone else encountered this sort of issue???

 

Thanks

[Magnet]

Hello Mohammed, 

Thanks for joining and posting your plea.

What we need to know is did the temperature gauge behave correctly immediately before you had the thermostat change? 
If so, it really would be a coincidence that a temperature sensor would have become troublesome at the same time that the thermostat was changed. Not impossible, but…..

I think that your assumption that this issue hasn’t anything to do with the thermostat ‘ …as it’s been changed..’. is indeed an assumption, based on new parts are not faulty. It would be great to think so, but experience shows that may not be the case. 
Is your reader capable of reading real-time coolant temperatures? I would think that this is what you need to be assessing. 
To me ( without diagnostics) the symptoms you are experiencing suggests a thermostat that doesn’t close and open  properly, but ……..

Kind regards,

Gareth. 

[RaffyS3]

Thanks for your input Magnet.

Yes I have had similar thoughts as yourself in regards to it possibly being a faulty new thermostat, but hoping it isn't as that is an expensive fix 😞

I have received the temp sensor today and will go ahead and change it tomorrow as long as the weather is okay. Will see if that fixes the issue. 

Before the thermostat was changed, I never had a gauge reader for the temp as the S3 only shows oil temp and not coolant. I bought an aftermarket gauge reader which connects to the obd and shows the readings of many things including the coolant temp, which is what I've monitored after the thermostat change and it's been erratic. 

Only thing stopping me thinking it's the thermostat is, yes because it's new and also the fact that if it was the thermostat I believe it would have erratic readings but not that dramatic as I'm getting and also the heaters would fluctuate in terms of the amount of heat they give but the heaters are always hot but only get cold when the temp goes below 30°c

Again that's just me wishing for the best and it not being the thermostat and hoping for a much cheaper fix

I guess I won't know for sure until I've got this temp sensor changed and see how she runs after that.

I will keep this post updated once I've done that

 

Kind Regards

 

Raffy 

[smokeymcnash]

Was there any update on this? Did that fix tbe problem or was it more? Been havi g the exact same problems and exact same symptoms, followed the exact same process and thought process in regards to changing the waterpump a second time after just having it replaced. Including the auxhillary water pump on the oil cooler. As i assumed as it was new that it was fine so wanted to avoid changing that again, when i say i am in the exact dame situation only difference is ive changed both the coolant sensors twice now and still having the same problems 

Edited December 5, 2023 by smokeymcnash

[Magnet]

Hello Randell, 

Regrettably, but as seldom happens, we never did have an update. 
Have you changed your thermostat!? 
Kind regards,

Gareth.