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Low Oil Temp And Very Low Water Temp...?

Discussion in 'A4/S4 forum(B5 Chassis)' started by rick the spud, May 15, 2007.

  1. rick the spud
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    rick the spud Member

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    reading some other posts on here i realise my water and oil temp temps are very low.

    on a decent drive my oil gets up to 70 but never higher, even on a long drive. the water temp hardly moves if at all from the bottom/60 mark, unless i stop in traffic or leave it ticking over in which case the temp starts rising, but when i start driving it starts dropping again, back to the 60 mark within 5 mins. it's never got to the 90 mark everyone on here seems to get!

    checked the water temp sender output on a vag-com and it seems to be the same as the reading on the gauge.

    wondered if was linked to my other problem:
    http://www.audi-sport.net/vb/showthread.php?t=38891

    any ideas?

    Rick
    #1
  2. johnie72
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    johnie72 Member

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    The water temp problem sounds tome like your thermostat is stuck open.
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  3. manwithbins
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    manwithbins New Member

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    Had the same symptoms on mine,changed the thermostat and gave the cooling system a good flush out and now the water sits at 90 degrees.Not too difficult to do either.
    #3
  4. tracer
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    tracer '96 a4 1.8 se

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    same thing happened on mine, thermostat stuck open.
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  5. rick the spud
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    rick the spud Member

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    surely on a long run the water and oil would get up to temp. i drove for about 2 hours the other day and it was still on the bottom.
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  6. enda1
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    enda1 Member

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    On a long run the airflow through the engine bay will keep the engine cool compared to being stuck in traffic. If the thermostat is stuck open then the water is constantly being pumped through the whole cooling system and radiator and so gets cooled and the coolant temp never gets upto the 90ish normal operating temperature. With a properly working thermostat the water will only circulate in the engine block until the water temperaure reaches approx 87C then the thermostat starts to open and the hot water starts to pump through the radiator. When on a long run the airlfow through the radiator is sufficicent to cool this hot water. When in traffic the airflow is in sufficient and if the temp keeps increasing the cooling fan cuts in to draw air over the radiator and cool the circulating coolant.
    As to the oil temp mine never gets above 70
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  7. rick the spud
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    rick the spud Member

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    cheers. i still would have thought the engine would have got up to temp on a long run, even with the thermostat open?
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  8. enda1
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    enda1 Member

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    If you're really thrahing it ,it will, but a long drive at part throttle, say 60 on a dual carriage way then the engine won't. The temp will reach a steady state where the airflow over the radiator is removing heat at the same rate the engine is putting it in. The thermostat overcomes this by keeping most of the water circulating in the block and only allows out the amount needed to keep the coolant constant. Its a mechanical feed back loop to control temp and the thermostat is the control mechanism so when it fails closed you get over heating and when it fails open you get cold coolant.
    This may cause the engine to overfuel and run rich as the engine temp sender is working properly and is telling the ecu that the engine is cold and thus will run rich constantly
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  9. rick the spud
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    rick the spud Member

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    cheers mate.

    thermostat it is.
    £4.85 + VAT, GSF.

    sweet...
    #9
  10. rick the spud
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    rick the spud Member

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    flushed the system a couple of times, changed the thermostat. sorted.

    took it for as run, 90 bang on. oil temp is up to 80-85 as well.

    checked the old thermostat and it seemed to be working though!?!
    #10

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