Tdi normal operating temp

Discussion in 'Mk3' started by DN5, Dec 29, 2018.

  1. DN5

    DN5 Paid Member Paid Member

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    What is the AHU Tdi normal operating temp?
    According to VCDS mine runs at 98°C once warm no matter what and the fans don't kick in. Temp guage a little above half.
    New thermostat has been fitted but should I be worried?
    I was told by RJ that the fans won't kick in until about 102°C but shouldn't these engines run at 90°C normally?
    Thanks, Rich
     
  2. DN5

    DN5 Paid Member Paid Member

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    Oh and for the record, I'm running in a mk2 using the smaller mk2 radiator and fans.
     
  3. rubjonny

    rubjonny Administrator Staff Member Admin

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    all sounds fine to me, the fan thermoswitch is set for 95degrees cut in on the 1st speed which is roughly 3/4 on MK2 gauge and 102 degrees for the 2nd speed. but note thats the temperature of coolant seen at the end of the radiator once its been circulated, rather than what the dash temp sees which is coolant temp at the outlet of the engine block before its been thru the rad.

    as long as thermostat is opening at around 90 degrees/around half and radiator gets nice and warm all the way across I wouldn't be worried at this point. the 8v rad is a fair bit smaller than what the mk2 diesels had as standard, so may want to keep an eye on temps as the weather gets warmer
     
  4. DN5

    DN5 Paid Member Paid Member

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    Thanks for the reply.
    So if all sounds well, I wonder why the fans don't kick in at 95c if the temp reading I'm getting at the block is nearer 100c.

    I'll check the radiator is starting to get warm at around 90c.

    I did previously look into changing the thermoswitch but didn't bother. Maybe I will just as a play safe. If be happier if the dash gauge was sat around half!

    I should also mention that the fmic is a really slim type that sits in front of the radiator thus taking the brunt of the cold air. Possibly this has some bearing on the higher temp reading.
     
    Last edited: Jan 2, 2019
  5. rubjonny

    rubjonny Administrator Staff Member Admin

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    when your gauge/vagcom shows 95 degrees, this is coolant temp as it straight after it leaves the engine block. the fan switch is located at the far end of the radiator away from the inlet and outlets, so it is sitting in coolant after it has passed through the radiator and it'll be a fair bit cooler than the engine temperature if rad is doing its job well.

    If the ambient temps are cool enough vs core size & quality the radiator will do fine keeping temps low enough that the fan never has to cut in, but you may find as it warms up the fans cut in more so keep an eye on it and see how you go :)

    changing the fan switch probably wouldn't help you get temps lower in this case, since usually you wont see it cut in till temps creep closer to 3/4 on gauge (1/2 is around 90 degrees). its probably more down to the size of the radiator vs intercooler I recon. I saw the same on my 16v cabrio while running a mk1 1.8 carb radiator, it's the same swidth as a MK1 GTI radiator but half the thickness and I found it would run about the same temps you see while driving about without the fan on. Changing to a proper dual core GTI rad fixed it straight away
     
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  6. DN5

    DN5 Paid Member Paid Member

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    My mind is at ease then until the summer at least :lol: I think I'm just in a panic that the gauge dared to move above what I deem to be normal!

    I do plan to get another fmic that sits under the slam panel but leaves bottom half of the radiator to the elements so should help out.

    Thanks again for the help, just the steering to sort now [xxx]
     

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