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More thermostat grief

Discussion in 'A3/S3 Forum (8L Chassis)' started by cerbera4_0, Mar 4, 2013.

  1. cerbera4_0
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    cerbera4_0 New Member

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    [Mar 4, 2013]
    So after replacing my stuck open thermostat at the weekend it appears the new one i put is now stuck shut!!!!

    Car overheated today, bottom radiator hose (one coming from thermosat housing) stone cold. I suppose that will teach me for not testing it first.

    My question is about the diagnostic display that you can bring up on the air con unit. I was monitoring channel 51, Engine coolant temperature. This started at ambient and steeadily rose to 90 degrees as you would expect. The instrument display lagged behind but caught up and levelled out at 90 for a good 20 mins of normal driving. Then the instrunment display started to rise until the high temp alarm came on. The air con display did not budge from 90 degrees which i found rather strange.

    Pretty sure the water pump is ok as can see water returning to the expansion tank and if i put my blowers on max it holds teh temp down a little bit.

    I guess I'm replacing the thermostat again tomorrow (after throughly testng the second new one).

    Does anyone know about the air con diagnoses readings and why they will not go above 90 degrees. I thought that this would monitor the temp sensor that feeds the instrument display.
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  3. cerbera4_0
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    cerbera4_0 New Member

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    [Mar 4, 2013]
    Just to re-inforce the water pump is working, with the old thermostat the temp gauge rarely budged off the 60 degrees mark unless at a stand still.
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  4. Broken Byzan
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    Broken Byzan Photographic Moderator Staff Member Moderator VCDS Map User

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    [Mar 4, 2013]
    How did you ensure it was bled correctly?
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  5. seanseansean
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    seanseansean New Member

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    [Mar 4, 2013]
    I am having the exact same problem - my thread is a few down from this A3 1997 Temp issue

    New temp sensor and thermostat fitted, old thermostat I took out was tested and fully working,

    How do you fully bleed the system?
    #4
  6. cerbera4_0
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    cerbera4_0 New Member

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    [Mar 4, 2013]
    the thermostat i took out was seized open. i couldnt budge it. I let the car get up to temp with the tank cap off. Surly with a car like this that is enough?

    Im going to change again tomorrow and test the one thats in there now and test a new one im picking up before changing. then I'll see how it is. the bottom hose was stone cold, aboslutely no heat in it. Is there a specific bleeding process. I did research it but couldnt find anything other than what i did.
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  7. joe91
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    joe91 New Member

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    [Mar 5, 2013]
    i thought that the 51 code was engine temperature? I know on my tt (bam engine) its 49 for engine coolant temperature
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  8. [Dave B]
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    [Dave B] Daddy

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    [Mar 5, 2013]
    When was your temp sensor last changed?
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  9. Vwdan80
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    Vwdan80 Member

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    [Mar 5, 2013]
    Did you use a genuine thermostat? These engines are normally pretty good at self bleeding as long as the return pipes are not blocked at all
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  10. Vwdan80
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    Vwdan80 Member

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    [Mar 5, 2013]
    Also when the thermostat is out you can feel the back of the water pump with your fingers to see if the impeller is intack and still connected to the pump :)
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  11. James TQ
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    James TQ Member

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    [Mar 5, 2013]
    you sure you put it in the right way? i done mine afew weeks ago, simple job, pain in the shooter as its behine the altinater though
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  12. rraghvani
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    rraghvani Whoever does not try, does not learn.

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    [Mar 5, 2013]
    Ensure the thermostat is the correct way around, and to the "burp" the car, leave the expansion tank open with air condition on full, rev the car a few times too. This will ensure that any trapped air is removed.
    #11
  13. cerbera4_0
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    cerbera4_0 New Member

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    [Mar 5, 2013]
    I have done plenty of thermostats so i am offended with the right way round comments.......Oh wait a minute. Egg on my face. Took it apart today a noticed straight away....**** thats it back to front. Why the f8ck would i do that. I put it down to tiredness and the freezing cold weather.

    thanks for replies guys much appreciated.

    seanseansean I would suggest you check yours is round the right way to save you the embarrasment i feel know :laugh:
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  14. seanseansean
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    seanseansean New Member

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    [Mar 5, 2013]
    Cerbera4_0

    I have fitted mine the same way I took the old one out,

    Does the longer end with the spring sit in the engine or in the plastic pipe?
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  15. Buzzer
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    [Mar 5, 2013]
    Had a similar problem myself, i could feel the water bubbling in the hose beside the airbox, ended up being the water pump had failed.
    #14

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