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Running temperatures that fluctuate?

Discussion in 'A3/S3 Forum (8L Chassis)' started by a318t, Jul 8, 2012.

  1. a318t
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    a318t Member

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    Hi all,

    In the search for finding out why my car is weak over 3,500 rpm, I've recently had a brand new water temperature sensor fitted, and my gauge shows me that every so often the car falls below 90 degrees (round about 80-85 I'd say).

    Is this normal?

    Every other car I've owned has stayed at 90 degrees once it's there. Never owned a car that falls below and then goes back up to temperature randomly?

    The new sensor isn't faulty because there are no error codes from diagnostic checks.

    Wondering if this is just a normal thing that 1.8T's do?
    #1
  2. s33nyboy12
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    s33nyboy12 Active Member

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    Got me worried now...... Mine does it lol

    Another thing is I've never had a car get / stay soooo hot under the bonnet! Damn Audi
    #2
  3. jamieA3
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    jamieA3 Member

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    Funny this thread just started, after a spirited drive today, I noticed to my slight amusment that when under hard acceleration ( 4000 revs plus ) my temp gauge goes down to about 75
    it goes back up as soon as i back off the gas. I was thinking thermostat needs replacing, any ideas anyone ?
    #3
  4. jamieA3
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    jamieA3 Member

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    not feeling weak though, so maybe our problems are different mate
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  5. <tuffty/>
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    <tuffty/> Badger 5 Edition Staff Member Moderator

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    Thermostat....

    <tuffty/>
    #5
  6. a318t
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    a318t Member

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    Yes haha. I'll turn my car off at 5:30 when I get in from work and it's still warm under the bonnet about 3 hours later....
    #6
  7. a318t
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    a318t Member

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    Mine does cool down when travelling along on motorways/A roads. Must be the fact that air is howling into the radiator?

    It seems to warm up MUCH faster when you leave it ticking over outside your house rather than driving it?!?!
    #7
  8. a318t
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    a318t Member

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    Will replace it for sure! By the way tuffty, thanks for your reply to my private message about TI pipes ;)
    #8
  9. superkarl
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    superkarl MAN OF STEEL

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    you can get an accurate constant reading of water temp through the climate control display.
    hold recirc and ^ together to access it, scroll to 49c using the temp +/- button, hit recirc to access 49c, this is coolant temp, the true reading from the sensor.
    by watching this you could determine whether its stat or sensor.
    a dodgy sensor won't register in vcds.

    i vote stat though, must be sticking
    #9
  10. Pabl0
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    Pabl0 Member

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    Should be bang on 90, all the time...

    Thermostat will be the main culprit, buy one from Audi and forgot :thumbsup:

    Oh, and have fun fitting it :haha:
    #10
    jamieA3 likes this.
  11. Sevv
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    Sevv Pushing the limits..

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    what he said... we all need the damn thermostat changed..:)


    i also change the coolant temp sensor and that happens atleast yours stay at 75/80 mine is at 60C ALL THE TIME lol!!! hopefully next week it will be sorted
    #11
  12. audia38l1
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    audia38l1 New Member

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    It could be the stuck thermostat as it keeps open when the engine is still cold.
    #12
  13. Sevv
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    Sevv Pushing the limits..

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    agreed mate... the annoying bit is as it stays open the ECU thinks the engine is still cold there fore is in overfueling mode as Mr. Tuffty so kindly explained which is the annoying bit
    #13
  14. aragorn
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    aragorn "Stick a V8 in it!" Staff Member Moderator

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    The ECU doesnt "think" the engine is still cold... the engine IS still cold, because the faulty stat is allowing it to be overcooled.
    #14
  15. boost-addict
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    boost-addict Member

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    am i right saying the thermostat is a cnut to change?
    mine can get up to temp. on motorways, a roads it does go down a little, will defently change both sensor and stat.
    #15
  16. <tuffty/>
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    <tuffty/> Badger 5 Edition Staff Member Moderator

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    Awkward but not difficult to change... there are a few guides about...

    <tuffty/>
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  17. jezzy
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    jezzy Member

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    If you use a quarter inch drive and socket on the thermostat bolts its a 30 min job. (you wont need to touch the alternator)
    Do what superkarl says first, might just be the sensor and thats a 1 minute job.
    Dont forget the coolant (pink stuff and expensive) if you change the thermo
    #17
  18. aragorn
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    aragorn "Stick a V8 in it!" Staff Member Moderator

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    tbh, i've never had a sensor fail yet. Its far more likely to be the thermostat.

    I've owned 5 or 6 1.8T motors, and every single one has required a stat (some multiple stats after cheap ones failed), and i've only changed 1 coolant sensor and even that turn out not to be required, as the starting issue was still there afterwards.
    #18
  19. superkarl
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    superkarl MAN OF STEEL

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    any of you wanting to change the stat, use genuine!
    cheap ones dont have very good reviews at all. and considering how fiddly it is (lots of swearing, its simple but bloody annoying) its best to do it right first.
    #19
  20. jamieA3
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    jamieA3 Member

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    It seems to warm up MUCH faster when you leave it ticking over outside your house rather than driving it?!?![/QUOTE]

    yeah definatly, takes ages to warm up if i drive straight away meaning i have to wait before the fun begins, trouble is, im usualy at work by then lol
    #20
  21. jamieA3
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    jamieA3 Member

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    btw, i just got a quote for a new thermo from an indy vag specialist....180 quid exc VAT...hahahahahaha jog on mate
    #21
  22. boost-addict
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    boost-addict Member

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    yeah definatly, takes ages to warm up if i drive straight away meaning i have to wait before the fun begins, trouble is, im usualy at work by then lol[/QUOTE]
    I get the same unless i drop kids and the witch off at work
    #22
  23. s33nyboy12
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    s33nyboy12 Active Member

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    Lol at the above threads, so a nutshell we stand it's the THERMOSTAT, and it's a bit difficult to fit....
    Would someone with limited mechanical knowledge like myself be ok?? I have all the gear but not a lot of idea :)
    #23
  24. superkarl
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    superkarl MAN OF STEEL

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    just takes patience and time my friend, if you have that, then you'l be fine.
    just have a friend on speed dial if need be.
    #24
  25. jamieA3
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    jamieA3 Member

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    just did this today. it is indeed the thermo as the readings match, however, when sitting in traffic the genuine reading is 83 even when the needle says 90. so dodgy thermo AND sensor ?
    #25
  26. superkarl
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    superkarl MAN OF STEEL

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    hi jamie, sorry i didnt get back to you in good time via PM.
    the temp gauge will always read 90 if temps are between something like 80-105.
    its designed to do this.

    although, you say you are at 83 in traffic, what is it when on the move? i imagine lower
    i would say you need a new stat.

    iv'e done 90 miles today, and on the motorway between 70-80mph my climate reading will always read 95/96 (needle at 90)
    my temp is pretty much at that allll the time. when i sit in traffic it does rise a tad. after a spirited drive it will go to 102 where the fans will kick in to cool it. on hot days after a hooning i've even seen 105 degrees, with the fans trying their hardest to get it down, which it does.
    hope this helps.

    p.s. always handy to have that true reading open when you go for a drive. for a better idea as to when the car is warm.
    shame there isnt an oil temp block.
    and if you want to know the rest of the blocks on the climate control it might be in the stickies.
    #26
  27. s33nyboy12
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    s33nyboy12 Active Member

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    Very helpful superkarl thanks
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  28. R-Tech-Nick
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    R-Tech-Nick Member

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    Optimised performance from the mapping will be around 92-98deg. If the ecu sees readings lower or higher it will add/minus correction to the main maps which can result in a reduction in power or a tad more power.

    Fluctuations in coolant temp can be down to ECT sensor, Thermostat or water pump. IMO its worth doing all three just for the sake of it.


    Nick
    #28
  29. a318t
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    a318t Member

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    Hi Nick.

    It had a brand new water pump October last year and as we spoke about, it had a brand new genuine ECT last week. It's having a brand new actuator fitted tomorrow, and I've asked my mechanic to inspect the thermostat...although as you say - worth doing anyway, it clearly isn't working right.

    Do you think this could be why my car feels 'flatter' than it did after the remap?

    Or, is there a chance that the extra stress from the remap has worn the spring in the actuator even more....hence why it feels 'flatter' than it did after the remap?

    Really can't wait to get it back to where it was after your map - it was superb!

    Byron (a318t)
    #29
  30. jamieA3
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    jamieA3 Member

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    very helpful thread this, cheers especialy to superkarl. nice 1
    #30

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