I have  2016 2.0L Auto Diesel Octavia with 38000m on the clock

I have a problem with  the the engine temp gauge, soon after start up the needle wavers up and down and then goes vertical and is steady at 90C far too soon, within about 5 mins of normal driving, at whatever time of day, the coolant level is at the max mark on the tank so there is enough. I thought maybe the water pump belt had broken but no problem there

I've had the car scanned and the only fault showing  is the no2 coolant sensor. I think that it is identified by either a green or blackcap. Can anyone tell me where this is located please ?

Thanks in advance.

 

Edited 1 June, 20224 yr by Obbor
missing information

Probably close to the point the lower radiator hose attaches to the radiator.

Engine code and the exact fault code might help to confirm. If engine code is a term you're not familiar with, see the relevant link in my signature.

If you can't see my signature, view on a computer instead of a phone.  

 

I'm not convinced that the rapidity of the gauge reaching 90°C indicates a fault though. Modern engines have partitioned cooling systems deliberately designed to hasten warm-up. Much more actively so than just a thermostat keeping the radiator out of circuit for a while.

Edited 1 June, 20224 yr by Pete_Ex-Wino

As an aside, this may be worth a read:

 

Gaz

 

Pete, 

Thanks for the reply,

 

Engine code CRMB  QMM

This started only within the last couple of weeks, the scan was carried out last night using a professional scanning laptop type thingy that showed that the number 2 sensor was at fault,

I know that there are 2 sensors in the cooling system but have no exact idea of their respective locations or colours, I believe the colour denotes the sensor number.

My normal run to work takes approx. 10-15 mins depending on traffic and the gauge normally doesn't get past 80C before I get to work. 

I don't mind buying a genuine part but don't want to get the wrong one and have to pay a restocking fee if it's the wrong one 

 

Gaz, 

Thanks for your reply,

The Cam belt and water pump were changed in April of this year at 36700miles (ish)

I think the QMM bit is probably your gearbox code, but scouring the parts catalogue for CRMB engine coolant temperature sensors has drawn a bit of a blank so far. 

This page should have one as item 9, but your engine code isn't in those listed, oddly: LLLParts

 

Thus far I haven't found a listing for a second sensor, despite looking in electronics and engine subsections.

I wonder if @nige8021 may have more success, with his greater familiarity with diesel engines?

 

This previous discussion suggests that I should have looked at wiring info instead of parts catalogue, and that you may be chasing unicorns looking for a sensor no.2: 

 

On the device we used last night it showed sensor 1 and sensor 2,  sensor  1 was at ambient, 15C , and sensor 2 was at -40C, after start up sensor 1 was slowly climbing while sensor 2 still read -40C, this leads us to believe sensor 2 is at fault

Edited 1 June, 20224 yr by Obbor

Sensor number 2 does not exist so you can ignore that.

 

You say it has only been exhibiting this behaviour for a couple of weeks and the waterpump was changed in April, pretty much the same time, the weather got a lot hotter between the two dates.

 

Other than the guage wavering what you describe to me is normal for a properly functioning system with the water pump sleeve and auxiliary pump, the guage would indeed read 90°c after 5 minutes driving in todays temperatures even though it is not a true reading, that it used to read 80° should be a big red flag, your engine was not getting up to temperature before, either a faulty or disconnected sliding sleeve or the previous pump was one without the system.

 

I would say your engine is now behaving as it was designed and it wasn't before.

My version of the wiring diagrams doesn't cover the 2016 Octy but the same engine code is fitted in the VW Touran & Seat Leon and they only show 1 coolant temp sensor.

 

The other thing is you seem to contradict yourself, in the first post you say it gets to 90c in a about 5 mins then your second post, after the 10~15 min drive to work it's only showing 80c ?? 

Nige 

I am not contradicting myself,

my first  post reads it gets to 90C  within 5mins,

my reply to Pete states that this has only started within the last couple of weeks whereas normally It doesn't get past 80C on my journey to work, 10-15 mins

 

J

In all the time I've owned this car I have never seen the needle waver, only steadily  move towards 90C on the gauge whatever the outside temp was, as I've said it normally only gets to 80C on work days but on longer runs it's steady at 90C and never moves.

As I've found out from this forum it's anything from 85ish to 105ish and still shows 90C.

It was alarming to see the needle creep up to 65 then drop back to 50  it did this twice then went straight to 90C and is still doing it

This is what lead me to have a scan done and ask the question about the location of sensor 2 and if there is no sensor 2 I don't understand how the the scanning device picked it up.

It didn't pick it up, it showed a default value for signal outside of parameters, lack of signal more like, rubbish in = rubbish out.

 

I am fairly sure that the needle wavering aside your vehicle is behaving correctly, you say "On the device we used last night  after start up sensor 1 was slowly climbing"

 

I suggest you take your friend as a passenger with the device connected and drive for 15 minutes from a cold satrt on your usual route, get him to look at the actual temperature readings compared to the indicated ones on the temperature guage, I reckon your engine will gradually warm up with a small hiccup as the water pump sleeve retracts and the auxiliary pump stops working, maybe another when the thermostat opens.

 

Dependant on the speeds and your journey profile I reckon your engine will be up to full operating temperature within 10-15 minutes and the guage will have shown 90°c some time before that.