Over heating Mk2 16v in nearly winter

Discussion in 'Engines' started by Matthew Walker, Dec 8, 2021.

  1. Matthew Walker New Member

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    Hello all.

    hope your all well.

    Just after some help and advice before I investigate an over heating fault on my Mk2 16v gti

    After the recent snow and cold spell My car decided dumped Its coolant out of the header tank. Initially I thought it was a split header tank but it turned out to be the seal on the cap. so I fitted a new cap but now but now I needed to look in to why my car is overheating causing this initial issue.

    Initially I checked to see if the radiator fan runs when the cars up to temperature (well over 90deg) and it didn’t

    so I’m just after a bit of insight/advice please going forward, is it most likely going to be the rad fan temperature switch in the radiator or could it be anything more sinister?? I’m going to test the fan tomorrow with a feed of the battery to eliminate a faulty fan, also when I run the engine with the cap off the header tank I can see coolant returning to the header tank so I’m thinking everything is ok with the water pump and that is pointing to the rad fan not running so is there anything other than the rad temp switch I should be looking at for theses types of symptoms??Also if I check the radiator temperature switch with a multi meter dose any one know what resistance I should get when tested at ambient /cold? Temperature I.e a reference point?

    TIA

    Matt
     
  2. H8V

    h8v Forum Member

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    The rad. fan switch is simply an on/off switch, not a variable resistance.

    Check the fan by pulling off the switch plug and jumping the plug contacts with either a piece of wire or paper clip. Two pin sensors are single temp, three pin sensors are low/high speed.

    You can test the old switch in a pan of boiling water, but new ones are not expensive. They have the operating temps stamped on them.

    What does the temp reading on the instrument panel say?
     
  3. rubjonny

    rubjonny Administrator Staff Member Admin

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    how hot on the gauge did you let it get? fan should cut in around 3/4. does the oil temp roughly agree with dash temp, 1/2 on gauge is around 90 degrees
     
  4. oldnick

    oldnick Paid Member Paid Member

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    The thermostat is working?
     
  5. PhilRyder

    PhilRyder Paid Member Paid Member

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    ^^^^ this, my first thought. Change it and give the system a flush.
     
  6. costel1969

    costel1969 Paid Member Paid Member

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    Yep, change the thermostat, flush the radiator, new coolant and you should be right as rain.
     
  7. rubjonny

    rubjonny Administrator Staff Member Admin

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  8. Matthew Walker New Member

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    Thank you everyone your advice is always appreciated.

    The temperature gauge went over half way I’d say it was on the 3rd mark when it normally sits in the middle the oil temp was 106 degC so I’d take a guess the coolant temperature was between 95-100 degas. I’d say they are reading similar.

    I’ve tested the thermostat and put new coolant in so it’s all good in that respect.

    so I took h8v advice and tested the fan and that runs so I’m going to change the temp switch in the radiator and see how that goes.

    thanks again guys
     
  9. H8V

    h8v Forum Member

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    That should fix it.
     
  10. Cressa Paid Member Paid Member

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    I think you have had all the best advice above to help solve your issue. Be nice to know what does sort it for you
     

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