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Temperature Sensor Issue

Discussion in 'A6/S6/Allroad forum (C6 Chassis)' started by youngw, May 12, 2014.

  1. youngw

    youngw New Member

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    Hi,

    I recently bought an A6 3.0TDi, the engine failed after one week. I have had another engine fitted (BMK) and the garage that installed it replaced the coolant temperature sensor in the process as it was not reading correctly. The car has been running fine but takes a long time to start from cold. Having looked into this a bit more I think it is down to then ECT sensor.

    When I first turn the ignition on the temperature gauge goes straight to half way (90 degrees) which I think is causing it to under fuel on start. When the car eventually starts and has been running a while, the gauge gradually moves downwards. Since this is a new sensor I can only assume there is an issue elsewhere, maybe wrong polarity on a connection or something?

    Has anyone had any experience of this before? Can't find anything on google that sounds remotely similar.

    Any help appreciated.

    Cheers,

    Wayne
     
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  3. B5NUT

    B5NUT Well-Known Member
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    Was it a genuine sensor fitted? It does sound like the sensor is at fault as it should not read 90 at cold startup. In my thread there is a small section on changing the sensor, make sure you get a genuine sensor from Audi. Also make sure you have some spare G13 coolant as you will lose some when you change the sensor.
     
  4. B5NUT

    B5NUT Well-Known Member
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    If you don't mind me asking what caused the original engine to fail?
     
  5. youngw

    youngw New Member

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    Hi B5NUT,

    It was unclear what had caused it. I was driving on the motorway when the oil pressure warning flashed on the dash, by the time I came to a stop the engine was a write-off. The conn rod went through the crank carrier and out the side of the engine, was a real mess. Until that point it was driving fine. I bought a second hand engine and had it replaced by a recommended mechanic, all in cost of repair £4000. Not want you want one week into ownership.

    I got to the bottom of my temp issue. Following your advice I got a new coolant temp sender from Audi this morning, installed it but the issue persisted. Having a good look around I noticed the same wiring loom has another connector on it which was plugged in elsewhere, I think it's a turbo temp sensor. I disconnected both, turned on the ignition and the temp gauge didn't move to 90 this time so I assumed they had got the connections mixed up when replacing the engine. I swapped them over and it started from cold immediately. Fingers crossed it will be fine now, I haven't driven it since as it has been taken for MoT which I hope doesn't result in any more costs as I already have a tainted relationship with this car as it is. Can't wait to get it back and see how it drives now.

    Thanks for your advice, I've a feeling I'll be needing more of it while I own this thing :)

    Cheers,

    Wayne
     
  6. youngw

    youngw New Member

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    Passed the MOT with no advisories. Phew!
     
  7. B5NUT

    B5NUT Well-Known Member
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    Good news on the MOT, but what a proper ...... about the engine. Where did you get the car from I take it there was no comeback.
     
  8. youngw

    youngw New Member

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    I bought the car privately. Gave it a good 40 minute test drive and everything seemed fine, just very unlucky I think and unfortunately no comeback. Did consider having the old engine dumped on their driveway :)

    Took it out for a spin last night, driving much better now, seems more responsive and the autobox seems smoother, those sensors sending the ECU duff info must have really been messing up the engine management.
     

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