Hi, new here

I had my octavia for 5 years now, no problems but always had this annoying problem.

63 plate 1.6 tdi manual mk3

Every 9 month to a year the temperature sensor goes. the dash starts showing the needle going up and down for a few days then it just reads zero. I changed it a month ago but this time it didn't last the "9 months". Its gone again. any reason why it keeps happening? Everytime I've changed it, the sensor looks corroded. And when I do take the sensor out, shouldn't all the water in the system come out? Cuz sometimes the coolant reservoir still has coolant in there. Maybe there's a blockage somewhere in the cooling system? Sorry for long post and any advice would be gratefully appreciated

 

Thank you

Which temp sensor are we talking about?

What are you replacing it with?

What part of the sensor looks corroded?

How sure are you its the sensor at fault, what have you done to diagnose it?

 

Are you saying when you take the sensor out, no coolant comes out?

Hi thanks

Its the Coolant temperature sensor

 

I've attached the pics so u can see the corrosion.

I have changed this part 5 TIMES so I know this is the culprit. But I wanted to know why is keeps going on my car and surely it shouldn't need changing every 9 months (1 month this time). I Don't think is a normal thing. 

When I take the sensor out the coolant does come out but shouldn't it all drain out? There is still some left in the coolant reservoir

Has someone used any coolant flush/additives in the coolant system that you know of?

Are you replacing with genuine VAG parts or some aftermarket sensor?

Bloomin eck!

 

I would flush the system vigorously and replace the coolant with the correct VAG grade.

 

Inconceivable that that level of corrosion could occur within one month, the coolant must be highly acidic.

37 minutes ago, varooom said:

Has someone used any coolant flush/additives in the coolant system that you know of?

Are you replacing with genuine VAG parts or some aftermarket sensor?

I've had the car for 5 years now. I have never used any flush. Just topped it up with the pink solution mixed with water and I'm putting parts from GSF part or EuroCarParts etc so I don't think they are genuine

29 minutes ago, J.R. said:

Bloomin eck!

 

I would flush the system vigorously and replace the coolant with the correct VAG grade.

 

Inconceivable that that level of corrosion could occur within one month, the coolant must be highly acidic.

Sorry that picture is from a month ago when I replaced the part. So that sensor in the pic was on the car for 9 months.

 

Not sure how the current  sensor is looking on the car but I know its gone as my temperature gauge on the dash is going zero to 90 and all over the place. Wanted to know what I can do to fix it properly so I don't need to replace it anymore

On 08/09/2022 at 12:56, ChickenLover said:

I have changed this part 5 TIMES so I know this is the culprit.

Sadly thats not how things work, in fact its the opposite. If you keep replacing the part and it keeps failing its a question of 2 things - The part is of a really bad quality every time. Or something ELSE is causing it to fail. I would first be checking the condition and concentration of that coolant, making sure its the correct one for the car and not just rubbish. 

Genuine coolant sensor looks to be only around £30, but I'd be highly suspicious that the real issue is contamination of the coolant.

Are you having to top up the coolant from time to time?

 

 

22 hours ago, Breezy_Pete said:

Are you having to top up the coolant from time to time?

 

No I never really need to top up. Maybe a tiny bit every 5 months and that's doing taxi mileage. Think that's normal. Yh ill check if its coolant contamination but as I said there still is some coolant left in the coolant tank everytime I changed the sensor.  So thinking if there's a blockage in the system. Is there another way to fully flush the system. How do I do it if I did it myself. Thanks

32 minutes ago, ChickenLover said:

No I never really need to top up. Maybe a tiny bit every 5 months and that's doing taxi mileage. Think that's normal. Yh ill check if its coolant contamination but as I said there still is some coolant left in the coolant tank everytime I changed the sensor.  So thinking if there's a blockage in the system. Is there another way to fully flush the system. How do I do it if I did it myself. Thanks

There will always be a small amount in the header tank, its not a hollow bowl, there are valleys and troths and coolant will get caught in there, the amount in there would hardly be enough to cause that level of corrosion. What coolant are you using, as in specifically what coolant. And how are you diluting it?

I'm was using the pink colour coolant from eurocarparts. Think it was the Comma brand. Pretty sure i diluted it as the instructions. Its finished now so can't properly remember exactly

16 hours ago, ChickenLover said:

I'm was using the pink colour coolant from eurocarparts. Think it was the Comma brand. Pretty sure i diluted it as the instructions. Its finished now so can't properly remember exactly

That could be part of the issue if you’re just throwing normal OAT/pink coolant in.

these cars are meant to have G13 coolant or evo coolant which is a more purple/violet colour.

 

it’s a different composition and it is a small possibility this could be causing the corrosion.

On 10/09/2022 at 16:07, ChickenLover said:

I'm was using the pink colour coolant from eurocarparts. Think it was the Comma brand. Pretty sure i diluted it as the instructions. Its finished now so can't properly remember exactly

As it's finished you will be buying more. Tell us what you plan to buy and someone will advise you if it's correct or not.

22 hours ago, ords said:

As it's finished you will be buying more. Tell us what you plan to buy and someone will advise you if it's correct or not.

Yh ill let u know. Think I'm buying the G13/evo and ill try to get a genuine temperature sensor from skoda/ VW

hope this is the last change 🤞

1 hour ago, ChickenLover said:

Yh ill let u know. Think I'm buying the G13/evo and ill try to get a genuine temperature sensor from skoda/ VW

hope this is the last change 🤞

If you are going to DIY this yourself, you want to make sure you follow what @J.R. said about flushing the system.

You will need several litres of distilled water for this task as well.

 

I think you can get away with draining, and flushing with standard tap water from a hosepipe (I might need correcting, but I am sure I have seen this in a VAG repair manual)

Flush it all through with lots of water.  You might need to flush it fully several times to be safe as you can be at this stage.

Then you will need to add your pre-mixed coolant made with distilled water and do all the bleeding.

Yh i got myself some distilled water from tesco. But I have a bad back so might get the garage to do it. BTW is there diy guide? I know how to do it but I can follow to see if I ain't missing any steps. Thanks

18 minutes ago, ChickenLover said:

Yh i got myself some distilled water from tesco. But I have a bad back so might get the garage to do it. BTW is there diy guide? I know how to do it but I can follow to see if I ain't missing any steps. Thanks

The official way involves equipment you don't have, so given your bad back, might be an idea to send it off to be sorted.

They absolutely must clean that system out for you, so hopefully a garage you have some trust with, and take in the old part or image to show them issue.

 

Best of luck