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Oil/water temp gauges not moving on 1.8t a4 quattro

Discussion in 'A4/S4 forum(B5 Chassis)' started by Chriscooke, Mar 18, 2012.

  1. Chriscooke
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    Chriscooke Clueless!

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    The oil and water temp gauges on my a4 1.8t quattro sport have stopped working. Is this a common issue? I have had a quick search but can not find the answer so sorry if it's been covered many times before.

    The car is also hesitant to start when warm after a drive and I wonder if the two are related?

    The average mpg has dropped down in to the mid 20's also which although the car is new to me seems a little poor.

    If anyone can help with any of the above issues I will be massively grateful :)
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  2. jonnycraig
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    jonnycraig Member

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    VAGCOM/VCDS is a good place to start, maybe someone on the forum lives near you to scan your car for you.
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  3. Chriscooke
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    Chriscooke Clueless!

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    I've heard of this but not 100% sure what's involved. Guess it's just plugging a laptop in to the car?

    If someone lives in somerset who is able to help or can advise a good local garage that won't rip me off that would be fantastic :)
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  4. jonnycraig
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    jonnycraig Member

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    There are many people on here with much more expertise than me but, yep it really is as easy as plugging a 'usb to audi' cable into a laptop running (very limited but free) software to give a basic list of any problem codes which you can search google to find out what they mean or ask on here. The leads are cheap off ebay £20 max.
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  5. Chriscooke
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    Chriscooke Clueless!

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    Sounds like a worthwhile investment then. Thanks for the tips. I'm a complete noob to VAG cars. I come mostly from a nissan background.
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  6. Broken Byzan
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    Broken Byzan Photographic Moderator Staff Member Moderator

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    the 2 have different sensors, so unlikey the faults are related. What stopped working first? When it was working, did it heat up to 90 degrees on both gauges?

    I'd start with replacing the CTS ( coolant Temp Sensor) as they are cheap and regularily fail, this tells lies to the ECU in regartds to temps, so it has no idea whether to warm srat or cold start. Also if its running on "Half choke" it will affect MPG
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  7. Chriscooke
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    Chriscooke Clueless!

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    Not sure which failed first tbh as I only picked it up a few hours ago. I know the previous owner so will ask him.

    The boost doesn't come in until 3.5k either so I thought I may have a boost leak somewhere also :(

    will I have to pay a visit to the main dealer for a sensor or are they available elsewhere?
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  8. aragorn
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    aragorn "Stick a V8 in it!" Staff Member Moderator

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    CTS or Thermostat is where i'd be looking.
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  9. Chriscooke
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    Chriscooke Clueless!

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    Will try the cts first as I guess this will be the easiest to replace. Where is good place for parts?
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  10. aragorn
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    aragorn "Stick a V8 in it!" Staff Member Moderator

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    The dealer for a CTS, i wouldnt use an aftermarket one.
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  11. Chriscooke
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    Chriscooke Clueless!

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    Definitely don't want an aftermarket one, was wondering if their is a cheaper supplier than going to an audi main dealer?
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  12. jamie226bhp
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    jamie226bhp Member

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    Only about £24 from dealer and that's full retail price
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  13. Chriscooke
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    Chriscooke Clueless!

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    Fantastic, hopefully a simple fix then :).
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  14. Chriscooke
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    Chriscooke Clueless!

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    Another proper noob question but is their a guide anywhere on how to replace the cts? I have no idea where it is or what it looks like :eek:
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  15. Bradderz_1988
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    Bradderz_1988 Dont replace it, Upgrade it !!

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    IIRC its at the back of the engine and on the tqs its a blue 4 pin connector and just has a push-fit clip holding it in place.
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  16. audiv6quattro
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    audiv6quattro Member

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    Yep cts is back of the engine, drivers side or at least on mine it is but Audi wanted £55 for a cts for my car.
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  17. Chriscooke
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    Chriscooke Clueless!

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    I'll ask in my local dealers on wednesday as i'm off work. Whats the deal with the ebay ones that have a 12 month warranty? Guess they are the normal ebay rubbish.
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  18. Chriscooke
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    Chriscooke Clueless!

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    I've now replaced my CTS which has made the gauge start working again :D The temp only gets up to 90oc when idling and ~80oc while cruising. I'm guessing i'll need to look at the stat also? The car now drives much better though and almost seems to be less laggy??

    I was hoping the new sensor would cure my rough start problems but they remain :(

    Here is a vid of my issue

    8dc809e8.mp4 - YouTube

    Can't seem to embed videos for some reason :(


    At the end where it almost stalled I gave it a little throttle and it roared in to life. Could this be fuel pressure related?
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  19. audiv6quattro
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    audiv6quattro Member

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    Temp should be at 90 mate that's normal any higher then I'd be worried, mine drops a bit when on motorway cruising aswell
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  20. aragorn
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    aragorn "Stick a V8 in it!" Staff Member Moderator

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    Your temp shouldnt move from 90. The guage has an internal buffer such that all "normal" operational temps will display 90. It only moves down from 90 if the temp drops below around 80c. If its moving around like that, your thermostat is faulty.

    Did you use a genuine Audi CTS?


    Mine does something similar on startup and i also changed the CTS trying to cure it, to no avail.

    Maybe not quite as bad as yours and definately not every time, but now and then it'll sort of half catch and mess around about 500rpm. If left alone when it does it, it will (at random) either stall or slowly right itself to 850rpm. If i dab the throttle when it does it, it'll rev up perfectly then drop to a nice idle just like yours does.

    I'd have suggested an airleak or split hose somewhere, but i cant find one on mine either!
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  21. Chriscooke
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    Chriscooke Clueless!

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    Thanks for your reply. I'll look at replacing the stat as well then. I got the cts from Audi as I had a search on here and realised the cheap ones are a false economy :)

    Edit: Does yours throw up any error codes at all?
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  22. NineNails
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    NineNails Proud sponsor of the snack food industry

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    Mine had similar issues with the idle until I did a proper throttle body adaptation which sorted it right out. Might not be your problem but thought it worth mentioning :)
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  23. Chriscooke
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    Chriscooke Clueless!

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    It idles fine once started so I think this may be a different issue. Worth looking at in time though I guess :) It's just the start up which is the issue
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  24. aragorn
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    aragorn "Stick a V8 in it!" Staff Member Moderator

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    Yeh mines exactly the same, only does it on start up on the odd occasion. No fault codes.
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