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2.5TDI - Correct Running Temperature?

Discussion in 'A4/A4 cabriolet/S4 forum(B6 chassis)' started by Seeker_UK, Jul 10, 2011.

  1. Seeker_UK
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    Seeker_UK Member

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    [Jul 10, 2011]
    I picked up my 2.5TDI Quattro Avant Tip yesterday and took it out for a long run yesterday. I noticed that the temp gauge never rose above ~70 degrees. Is this correct or is there a problem?

    It's going in for a service next week so I can ask them to sort it but a few pointers would be useful.

    Thanks
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  3. mikeh126
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    mikeh126 Member

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    [Jul 10, 2011]
    I have been told that the correct temp should be 90 degrees, give or take a couple.
    The engine is running cold, if it only reaches 70 degrees.

    I hope it's not a faulty thermostat - it's a fairly major job to change it.:ohmy:
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  4. donsajid
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    donsajid Member

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    [Jul 10, 2011]
    if it is thermostat, then you may as well get timing belt and water pump done same time, stafford audi will do it for ~500GBP
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  5. Seeker_UK
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    Seeker_UK Member

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    [Jul 10, 2011]
    Not v.happy about having to do the belt & pump a year early but if it has to be done, it has to be done.

    [edit]

    Replacement thermostat should be covered by the warranty so I'll check there first.
    Last edited: Jul 10, 2011
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  6. JimLoskot
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    JimLoskot Member

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    [Jul 10, 2011]
    probably just the sensor ontop of the engine, easy to change. temp should be 90
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  7. Seeker_UK
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    Seeker_UK Member

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    [Jul 10, 2011]
    Thx - is there a DIY anywhere on how to do that?
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  8. JimLoskot
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    JimLoskot Member

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    [Jul 10, 2011]
    its the cooler temp sensor. its here:
    [​IMG]
    basically take the metal braket off to make access easier, unplug, take out and put new one in, and plug back in. you won't lose any coolant. seem to remember mine was really difficult to get out because it had seized in a bit and had to use mole grips to pull it out.
    #7
  9. quattrojames
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    quattrojames Moderator Staff Member Moderator

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    [Jul 10, 2011]
    That looks suspiciously like my engine!

    As I found out to my cost last week .... :(
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  10. Az
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    Az Hard slammed!

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    [Jul 11, 2011]
    This seems to be very common on the 2.5tdi, I had to have my thermostat changed along with cambelt and water pump last September due to the engine running cold. The cambelt was only changed about 20k miles before hand but who ever changed the belt last didn't change the thermostat as a precaution. When they pulled the stat out they showed me it and it was seized and covered in rust.

    Makes me laugh when garages do that, (well it didn't make me laught when it cost me £700) for the sake of a £17 part I don't know why it's not just changed for the sake of it at the same time.
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  11. Seeker_UK
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    Seeker_UK Member

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    [Jul 11, 2011]
    Thanks for all the replies so far.

    What I'll do is get the temp sensor changed next week when I get it serviced and if that doesn't sort it, I'll get the thermostat replaced under warranty.

    One other thing, if the ECU is receiving a water temp reading of only 70 degrees (either because of the sensor or the thermostat) would that cause the poor fuel consumption I'm getting? I did a 220 mile round trip on Saturday (mostly m-way and a-roads) and I've used half a tank fo fuel which works out at 30-32 mpg (depending on whether the tank is 62.5 or 66 litres) which seems a bit excessive. :ermm:
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  12. quattrojames
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    quattrojames Moderator Staff Member Moderator

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    [Jul 11, 2011]
    It'll be a 66 litre tank, I average 32 in mine so you're probably about there. A new CTS might help though.
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  13. Seeker_UK
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    Seeker_UK Member

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    [Jul 11, 2011]
    Thx but that's 32 mpg after a steady run at 70 for 200 miles. That can't be right, surely?!?! That's nearly as poor as the CLK320 cab I used to own.:ermm:
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  14. neilA4
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    neilA4 Member

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    [Jul 11, 2011]
    My stat needs changing too. I have got 450 miles from full tank and the fuel light has just come on the dash, dis computer is showing 37mpg. Should be better when i do the stat/waterpump/belts etc.

    But yours is a triptronic/auto so prob where the difference is.
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  15. Seeker_UK
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    Seeker_UK Member

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    [Jul 11, 2011]
    Let's just confirm this.

    Is it "normal" to get 32mpg on an A4 2.5TDI Tip Quattro 'on a run' (not mixed driving)? Because if it is, I've definitely bought the wrong car. :sadlike:
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  16. quattrojames
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    quattrojames Moderator Staff Member Moderator

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    [Jul 11, 2011]
    I'd say it's probably a tad low, but if you bought the 2.5q for economy you've bought the wrong car! That said for the performance it will give you probably 10 mpg more than the equivalent petrol.

    I'd sort the running temp. out and go from there.
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  17. Seeker_UK
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    Seeker_UK Member

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    [Jul 11, 2011]
    I did all my sums before buying it and knew it wasn't going to be as frugal as my previous A6 2.7TDI or even BMW 330CD, given it's "old school" 5-speed auto & AWD - but the trade-off is that it's cheaper to buy / insure. However, my yardstick is Mrs Seeker's A6 2.4 SE Multi - it's similar performance and returns 32mpg average so I'm expecting better.

    Anyway, we shall see after the service / repairs. :)
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  18. BlackQuat
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    BlackQuat Well-Known Member VCDS Map User

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    [Jul 11, 2011]
    I recently did a 1400 mile round trip to le mans and back. 3 people in the car and a boot full to the brim with camping gear and returned 43mpg. That was 70-80.
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  19. swarcup
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    swarcup Well-Known Member

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    [Jul 11, 2011]
    when i bought mine i had the thermostat issue and can say that once done it made the mpg go up a few.
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  20. JimLoskot
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    JimLoskot Member

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    [Jul 11, 2011]
    also worth doing the brake switch as that went on mine not long after and then my clutch switch went not so long ago. not sure if this is a problem on the auto's or what the switch arrangment is down there
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  21. Mike B
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    Mike B Member

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    [Jul 11, 2011]
    If its the stat you s/b able to tell from the heater not working efficiently also the rad will start to warm up immediately from cold.If the heater seems OK and the rad stays cold initially then its might well be the cts.Beats me why some stats dont last I think its worth insisting on a good one and same for the pump and belts cos there are said to be cheap ones that dont last.We have a Trip and manual and 32 is too low for a cruising mpg even the Auto will do 40ish but it suffers in traffic cos you cant keep the revs down like you can in the manual
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  22. Seeker_UK
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    Seeker_UK Member

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    [Jul 11, 2011]
    What are the best brand of thermostat to go for?

    Get one from Audi?
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  23. JimLoskot
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    JimLoskot Member

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    [Jul 11, 2011]
    probably
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  24. Turkster
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    Turkster Bro.Paul 2.5TDI Quattro Sport

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    [Jul 11, 2011]
    Audi for the part mate, i had the same issues as you, was the thermostat that was rusted open, cam belt off time and new water pump, so new ones on!
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  25. Seeker_UK
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    [Jul 18, 2011]
    Just an update.

    The car was serviced today and the specialist checked the car over.

    It wasn't a busted thermostat but a seized viscous coupling on the fan. The specialist advised that this was clobbering the fuel consumption 2 ways: constantly running the fan uses more fuel and running cooler uses more fuel too.

    Also, a gasket on a connector on the EGR pipe had disintegrated and apart from a drop in boost, this also has a bad impact on fuel use.

    Hopefully, when the fan is sorted, we're all fixed for the year.
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  26. Mike B
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    Mike B Member

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    [Jul 18, 2011]
    Lets hope that this does it.Seems a lot for the fan to keep the temp down by 20 if the stats OK.Let us know!
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  27. swarcup
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    swarcup Well-Known Member

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    [Jul 19, 2011]
    the viscous fan runs permanently anyway, it just speeds up with the revs.these engines run hot so need the extra cooling permanently. From what ive read and experienced 99% of the time its the stat.
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  28. Seeker_UK
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    Seeker_UK Member

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    [Jul 19, 2011]
    And it's s*d's law, my car is the 1% it isn't.:blink:

    The garage tested the thermostat and found it was opening /closing when it should.

    The fan coupling was totally seized so it was running at full speed all the time, not just when the engine temp was >90.

    Whilst this is sort of good news, it means that it might not be covered by the warranty.
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  29. adamss24
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    adamss24 Well-Known Member

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    [Jul 19, 2011]
    I have been working on a few v6 tdi so far (some forum memebers can vouch for that) and i never found a seized solid viscous fan, they bearing either starts desintegrating and the fan will cut into the radiator (done a few dozens like that) and every v6 tdi witch had an over-cooling problem it was the thermostat. I don't trust garages especially when it's easy to blame another part and pass the costs to the customer ! It's easy to check the viscous fan: get a rolled newspaper and try to stop the fan spinning when engine is cold. If it stops then the fan is fine. With the engine hot the fan will be tricky to stop.
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  30. Mike B
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    Mike B Member

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    [Jul 19, 2011]
    Chris knows his 2,5 Tdis and I can say that my 70s Spitfire with its fixed coupled fan still gets to full temp albeit slower than if it had a temp controlled one.How did they test the stat without removing it?the engine should get to full temp before the stat opens and the fan only serves to draw air through the rad when its hot.These are water cooled not air cooled engines like my early Beetle which needed a huge fan for a little 1200cc engine and made most of the noise
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  31. Seeker_UK
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    Seeker_UK Member

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    [Jul 19, 2011]
    Thanks for the replies. I have no reason to doubt the specialist on this - we've used him for 6 years and he's never been wrong yet.

    Also, they had nothing to gain from misdiagnosing the fault - they're not going to get paid for the work as it's a warranty job.

    That said, if I get the fan swapped and it's still running cool, then it'll be a 'stat problem and I'll let you know.
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  32. adamss24
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    adamss24 Well-Known Member

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    [Jul 19, 2011]
    I am just speaking from my experience, not slating your mechanic- i have yet to see a seized viscous coupling, been working with cars since i was 5 and not had the chance yet ! Every one i worked on (either mercs, beemers or vags) used to overheat if the viscous fan failed NOT overcool. I still think is pointless boiling the stat just to make sure it works...it's not a fool proof method. Genuine stat for mke though allthough i have fitted a few cheappo stats onto v6 tdi (from ECP at owners requests!) and had no trouble whatsoever but, i would rather spend £20 on a genuine part even though the £6 pattern part is just as good !
    #31
  33. Seeker_UK
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    Seeker_UK Member

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    [Jul 20, 2011]
    That makes two of us. :thumbsup:
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  34. Mike B
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    Mike B Member

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    [Jul 20, 2011]
    Lets hope your man is right but as Chris says you can easily check the fan yourself . if the rad starts to warm up too soon that indicates a stat stuck open as they are meant to if they fail then the engine will not get to 90
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  35. Seeker_UK
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    Seeker_UK Member

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    [Jul 25, 2011]
    Just an update.

    The workshop at the garage I got the car from have now diagnosed a faulty 'stat.

    The good news is they'll get it repaired under warranty.

    Even better news is that as they're in there, I can get new belts / pump done for cost of parts. Result!
    #34
  36. swarcup
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    swarcup Well-Known Member

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    [Jul 25, 2011]
    RESULT! thats one of the larger bills sorted for cheap then. what was the viscous fan result? was it duff or simply mis-diagnosed
    #35
  37. Seeker_UK
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    Seeker_UK Member

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    [Jul 25, 2011]
    Good question.

    The supplying dealer is going to get a local VAG specialist to do the work so no doubt, they'll have another look just ot make sure.
    #36
  38. adamss24
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    adamss24 Well-Known Member

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    [Jul 25, 2011]
    I am soo looking for the button with "i told you so !" but i know i will look shmuck so i better get my coat ! Be glad they'll sort-it under warranty as it cost a few bobs to do...
    #37
  39. Seeker_UK
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    Seeker_UK Member

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    [Jul 25, 2011]
    I was waiting.

    A difficult one really: On one hand a reputable indy, on the other someone with loads of experience but w/out the luxury of being able to get hands-on.

    Thanks for the advice though.
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  40. Seeker_UK
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    [Jul 28, 2011]
    Final update

    Work all done and needle bang on 90.

    Now, the next thing is to sort out the wheel arches. Taking off the bumper has knocked off a few rust scabs exposing metal. More expense. :sob:
    #39
  41. Turkster
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    Turkster Bro.Paul 2.5TDI Quattro Sport

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    [Jul 28, 2011]
    No that makes 3 of us :icon_thumright:
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