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heater luke warm

Discussion in 'A4/S4 forum(B5 Chassis)' started by tom-craig@hotmail.co.uk, Aug 10, 2011.

  1. tom-craig@hotmail.co.uk
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    tom-craig@hotmail.co.uk Member

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    [Aug 10, 2011]
    hi recently got a 98 a4 18 se avant,this morning travell to work 4 miles heater wont blow warm air,took the longer run home tonite 8 miles and heater luke warm,temp wont rise above 70,stopped and checked hoses top hot bottom from the rad cold,and on restarting the engine the temp touched 90 breifley before dropping back down when i drove off,is it the thermostat:uhm:
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  3. Blue_Thunder
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    Blue_Thunder Active Member

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    [Aug 10, 2011]
    Sounds very much like it.
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  4. B5NUT
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    B5NUT Well-Known Member VCDS Map User

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    [Aug 10, 2011]
    I would say the stat is stuck open.
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  5. tom-craig@hotmail.co.uk
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    [Aug 10, 2011]
    being a no brainer with engines,if the top of the engine is hot and the bottom cold and the stat is open why isnt the water at an even temp thruout the engine as it is being pumped round
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  6. S4_dan
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    S4_dan Fire up the Quattro! VCDS Map User

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    [Aug 10, 2011]
    I'd say blocked radiator. Had this on a Matiz. Top a rad hot, bottom cold as that is where all the sludge was sat. Gave it a good flush with a hose pipe and all sorted.

    If stat was stuck open, then i'd agree all the pipes would be same temp but cool.

    could be heater matrix that is blocked too though. Check the hoses going into and out of the matrix from the engine bay bulkhead.
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  7. B5NUT
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    B5NUT Well-Known Member VCDS Map User

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    [Aug 10, 2011]
    The rad is designed to cool the water going through it, also the heater matrix inside the car will also be cooling down the water. It should be hotter at the top than at the bottom, heat rises etc.
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  8. S4_dan
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    S4_dan Fire up the Quattro! VCDS Map User

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    [Aug 10, 2011]
    There wouldn't be a massive temp difference though as the car is stationary whilst feeling the pipes so the water wont be cooling that much compared to the top pipes?
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  9. B5NUT
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    B5NUT Well-Known Member VCDS Map User

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    [Aug 10, 2011]
    If the rad was blocked the engine would over heat, same as if the stat was stuck closed, the only way to then cool the engine would be to put the heaters on full.

    Used to do that trick on an old Volvo, if the car was sat at idle I would start to over heat putting the internal heaters on full dropped the coolant temp back to 90.
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  10. B5NUT
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    B5NUT Well-Known Member VCDS Map User

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    [Aug 10, 2011]
    The rad has to cool the water going through it otherwise the engine would over heat, you have the viscus fan sucking air through the rad and a backup electric fan if the temp climes.
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  11. tom-craig@hotmail.co.uk
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    tom-craig@hotmail.co.uk Member

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    [Aug 10, 2011]
    Mmm drove 20 miles tonite engine up to 90,heater still blowing cold,the matrix is not leaking,top rad hose to hot to hold on to for long,bottom hose luke warm ,both heater inlet and outlet pipes hot,although one was hotter than the other but still no hot air,anyway luckily for me my son is the sales manager for our local seat dealer,so mates rates car is booked in for a thermostat change,well see if it makes a difference
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  12. B5NUT
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    B5NUT Well-Known Member VCDS Map User

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    [Aug 10, 2011]
    Were the two hoses going into the car hot, these are the ones next to the battery?
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  13. tom-craig@hotmail.co.uk
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    tom-craig@hotmail.co.uk Member

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    [Aug 10, 2011]
    yes mate 1 was hotter than the other
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  14. B5NUT
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    B5NUT Well-Known Member VCDS Map User

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    [Aug 10, 2011]
    That sounds about right, Do you have aircon?
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  15. tom-craig@hotmail.co.uk
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  16. B5NUT
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    B5NUT Well-Known Member VCDS Map User

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    [Aug 10, 2011]
    If you have access to vcds then you could check for fault codes, the motors that control the flow of air across the heater matrix haven been know to stick or fail. The first cheap option is to change the stat & the temp sensor. Also if the coolant is looking a little on the brown side then a good flush out and refill with a couple of bottles of G12
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  17. tom-craig@hotmail.co.uk
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    tom-craig@hotmail.co.uk Member

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    [Aug 11, 2011]
    Cheers for the replys.gonna change the stat and sender and a flush out.will post the results
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  18. tom-craig@hotmail.co.uk
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    tom-craig@hotmail.co.uk Member

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    [Aug 13, 2011]
    ok changed the thermostat today genuine with seal 20 quid,full flush out lots of ****,and whey hey heeeeeeeeeeeeet,the bottom hose is now hot as well no dramas feel lucky that it was that simple,and fingers crossed that was the problem,drove 30 miles heat on and off swapped and switched the air con on and then full heat,90 all the way and oil about the same
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  19. B5NUT
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    B5NUT Well-Known Member VCDS Map User

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    [Aug 13, 2011]
    Always good to get a first time fix.
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  20. tom-craig@hotmail.co.uk
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    [Aug 17, 2011]
    update,sunday went to vw fest at hareward house good show,sat on 2.5 miles of non moveing traffic,bricking it in case it over heated,but hey it must of done good now no air locks in system and even on a 3.5 mile journey to work in the morning warm air blowing so deffo seems to have done the trick,2 weeks time on holiday in scotland 300 mile drive a deffo test on reliability
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  21. Baza1819
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    Baza1819 Member

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    [Jan 27, 2013]
    I will have to try this then - my heaters a piss poor - saying that the pipes going into my 2.0 tdi sportback are not hot ?
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  22. Baza1819
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    Baza1819 Member

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    [Feb 6, 2013]
    Mind fixed
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