C8 Temperature gauge/sensor problems

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jscadden
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C8 Temperature gauge/sensor problems

Post by jscadden » 13 Aug 2019, 18:07

I know this topic is live elsewhere but my problem is somewhat different.

When I switch on, my temperature gauge goes to 130degrees along with warning lights etc. After a while, but not every time, the needle will flicker a couple of times between 130 and 100 and then go down to 90. Over the next few minutes, it will slowly sink to 50. On the odd occasion, it will start at 50!

If I switch off while the gauge displays 130, the fans will go on for a time.

I have changed the Coolant Temperature sensor twice in my one year of ownership and I know from RAC records that it has been changed before. The last one lasted almost three months.

The car in question is a 2005 2.0HDi Auto.

Regards,

John

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Re: C8 Temperature gauge/sensor problems

Post by admiral51 » 13 Aug 2019, 19:25

Welcome to the forum/family John.
Post your Vin number as this will help those with greater knowledge than myself to help.

Do not worry your Vin will only be visable to forum Admins.
I have my Vin posted in my signature, so much easier, just post a question and Vin is there :)

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GiveMeABreak
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Re: C8 Temperature gauge/sensor problems

Post by GiveMeABreak » 13 Aug 2019, 19:47

Yes, we need the VIN as there were 6 variants of the 2.0 HDi engine

jscadden
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Re: C8 Temperature gauge/sensor problems

Post by jscadden » 16 Aug 2019, 23:34

I've put the VIN in the signature as suggested!

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Re: C8 Temperature gauge/sensor problems

Post by GiveMeABreak » 17 Aug 2019, 01:25

What about the Engine thermostat? Item 7 on the left diagram and 3 on the other? Part 133823
Also some water temp sensors on the aftermarket aren't up to much. Part 1338C1 (item 9 on the left and 6 on the right diagram).
C8 Cooling.PNG
C8 Cooling B.PNG

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white exec
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Re: C8 Temperature gauge/sensor problems

Post by white exec » 17 Aug 2019, 07:28

Agree with Marc's suspicion about the thermostat - it sounds like a sticking one, reluctant to initially open, then allowing a sudden volume of cool water through. Action should be gradual and progressive.
Cheap enough to replace; make sure it comes with a fresh gasket/O-ring.

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Re: C8 Temperature gauge/sensor problems

Post by moizeau » 17 Aug 2019, 09:49

Not sure about the thermostat because John states that it reads 130 degrees when first switched on? Could you confirm, John, whether the engine is running or just the ignition? If the engine is running, does it show the high temperature straight away on a cold engine? The symptoms that follow, however, do point to a sticky thermostat.

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Re: C8 Temperature gauge/sensor problems

Post by white exec » 17 Aug 2019, 12:39

Agree, Pete. Faulty 'stat would not produce 130C with a cold engine. #-o

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Re: C8 Temperature gauge/sensor problems

Post by jscadden » 17 Aug 2019, 17:02

It is extremely unlikely that the fault is with the thermostat. The temperature gauge can display both ends of the range in seconds and has never physically overheated. Having stood overnight, it is not possible that the engine temperature could still be 130 degrees. The last two sensors were purchased from GSF and they did make sure it was the correct one for the car.

I recently drove over 100 miles with the gauge reading 130 most of the way then 50 for a period before going back to 130. As the needle flicks about at times, this points to something electrical. Does this system have an ECU?

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Re: C8 Temperature gauge/sensor problems

Post by admiral51 » 17 Aug 2019, 17:20

If we assume the dash display is correct as it reads both ends of the scale, and thermostat would not give a reading ? then for arguments sake what is the cheapest option ?

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white exec
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Re: C8 Temperature gauge/sensor problems

Post by white exec » 17 Aug 2019, 18:57

Maybe remove the temp sensor, and immerse it in known-temp water, IGN on, and see what the gauge reads.

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Re: C8 Temperature gauge/sensor problems

Post by jscadden » 20 Aug 2019, 14:09





I'm not sure whether you can see the videos as it's the first time I've ever done this.

They show the start-up of the vehicle. This was after standing overnight for more than 12 hours.

The vehicle is currently on its third coolant temperature sensor in just over a year.

John
Last edited by GiveMeABreak on 20 Aug 2019, 14:12, edited 1 time in total.
Reason: Fixed YouTube Links

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GiveMeABreak
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Re: C8 Temperature gauge/sensor problems

Post by GiveMeABreak » 20 Aug 2019, 14:13

John - I've fixed the links, but you have not set the permissions correctly in Youtube. The videos are probably set to private. You need to make them available to anyone who has the link or set to public.

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Re: C8 Temperature gauge/sensor problems

Post by jscadden » 20 Aug 2019, 14:38

I've reset them to Public. You should be able to view them now.

John

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Re: C8 Temperature gauge/sensor problems

Post by GiveMeABreak » 20 Aug 2019, 15:15

This is the wiring between the Temp coolant Sensor (1220) and the Engine ECU (1320). Given that you have had 3 sensors - I would be suspecting the plug or the wiring to the engine ECU. I would suggest taking the connectors off the sensor - checking to see if the pins are making good contact (sometimes they can retract causing an intermittent connection) and then clean them up.
coolant.PNG
The Sensor plug should be a 2 pin green plug with the following wires:
4000: Coolant Temperature Sensor Earth (Pin 1)
400: Coolant Temperature info (Pin 2)

They go to the engine ECU 48 pin Brown plug on pins D1 and E1

This is the location of the earthing points - so I would check the MC15 and MC12 earths which both concern the engine ECU. Make sure they're not rusty or making poor contact.


Click Diagram to Zoom
Earths.PNG