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Heater only blowing warm

Discussion in 'Audi S4/A4/A4 Cab (B7 Chassis)' started by Coath, Oct 10, 2013.

  1. Coath
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    Coath New Member

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    [Oct 10, 2013]
    So , the first cold morning today so i decide to crank up the heater, it is only blowing warm air but gets hotter whilst driving at 60mph, temperature gauge reaches 90 fine.

    I know the thermostat housing is leaking slightly, i have the new one which will be replaced shortly would this be having any effect ?

    Coolant is g12

    Does anyone have any suggestions where to start ?

    Thanks in advance
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  3. NHN
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    NHN Retrofitter - Audi - VW - Skoda - Seat Site Sponsor VCDS Map User

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    [Oct 10, 2013]
    Fix the leak 1st and maybe consider changing the thermostat at same time to discount this given you're in that area, if its not too expensive, then see if its improved.

    I always work on basis if there are existing known multiple issues, they need resolving ideally 1st before looking for new issues not known of.
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  4. Coath
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    Coath New Member

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    [Oct 10, 2013]
    I read a few articles on various forums for things to check , so this evening I checked both inlet and outlet hoses going into the matrix, both are getting hot , I bled the system didn't seem to have any air in there , I did notice that the bottom hose coming from the coolant bottle is not getting hot ?

    Would a faulty/leaking thermostat housing cause only warm air to the cab and hot air whilst driving at speed ?

    Could it be the motorised flaps, if so how would I check these

    Thanks
    #3
  5. Mike B
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    Mike B Member

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    [Oct 10, 2013]
    I would say leaking stat which is stopping it warming up quickly.The flaps would prevent it giving heat at all speeds.Easy enough to remove the glove box and see if they are working OK.The temp gauge is not precise.Dodgy stats have been a bane of my decades of motoring.They don't seem to be any more efficient or reliable than 50yrs ago
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  6. Coath
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    Coath New Member

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    [Oct 11, 2013]
    One thing I forgot to mention is that last night whilst trying to bleed the system I had the coolant cap off to try and get rid of any trapped air, So I ran the car up and all was fine for a little while, but then the coolant level started to rise to the point it was over flowing from the header tank , Would a faulty thermostat cause this ?

    I am going to replace the thermostat housing tomorrow , I hope this cures the problem
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  7. Mike B
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    Mike B Member

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    [Oct 11, 2013]
    The system relies on the cap sealing tight to allow the pressure to keep the temp down.Same as you musnt remove the cap when hot cos it will throw hot coolant at you
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