Z32 Cooling fan question and introduction

Discussion in 'Technical' started by Niek, Aug 7, 2020.

  1. Niek

    Niek New Member

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    Hello everyone.

    Since approximately 4 years now I'm a (most of the time) happy owner of a Z32 TT 1990 sin, living in the Netherlands. A lot has been done to keep the car in good shape after years of probable abuse by younger owners not taking care of it (also found already great tips before on this forum which saved me a lot of money)

    At the moment I'm experiencing some overheating issues (about 30 degrees outside temp.in the Netherlands at this moment). It mostly occurs while driving on the motorway. I have found this comprehensive thread on this forum (http://www.pexcom.com.au/z32cms/e107_plugins/content/content.php?content.465) which I definately will review. I just replaced the thermostat and it has improved the meter gauge reading overheating, but still after a while the gauge moves a bit to the hot area (a bit above middle, before the replacement a lot higher).
    My question relates to the fan. If turn off the car the fan immediately stops. When I turn the engine on again after a couple of minutes the fan starts again, but the temperature gauge on the dashboard then shows the meter almost al the way in the hot area. It slowly then goes down again while driving. Is this normal?
    Thanks for the help :)
     
  2. IB

    IB ?????

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    Have you got the front under tray? The one between the bumper and bottom of radiator? If that is missing you're likely to get the overheating issue you describe.
     
  3. Niek

    Niek New Member

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    Hi Ian. Thanks for your quick reply. Not 100% sure what you mean, so I took some pictures. Hope that helps. Previous owner did install a front turbo intercooler vs the Original left/right ones. but so far that never caused any problems
     

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  4. IB

    IB ?????

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    Both under trays are missing from your pictures. The air going through your bumper goes under the car instead of going through the radiator.

    At motorway speeds, the front under tray is more important than the fan.
     
  5. Niek

    Niek New Member

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    Ow that’s a shame. Although so far it never caused any issues. Any ideas on my fan question? Thanks in advance
     
  6. IB

    IB ?????

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    Your first post said you were experiencing overheating issues mainly on motorway, the missing under tray most likely the cause.

    Fans do their cooling work at low road speeds.
     
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  7. jellybeans

    jellybeans Active Member

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    Hi Neik,

    I have a front mount and have not had any overheating issues so have not read any in-depth or specific 300zx posts like the one you quoted. They will contain a lot more information than what i will tell you here.

    As IB has already said airflow is more important than fan at speed, or to put it another way, of greater volume.
    The fan is only used to cool the radiator while stationary or at low speeds where the airflow into the front of the car is insufficient.
    Your radiator only has small gaps for air to pass through so the air will want to go around rather than through if there is an easier path. Having an aftermarket front mount will increase the tendency for this. The plastic guides blank off these easier paths and the air must force past the intercooler and radiator therefore increasing the amount of heat exchanged.
    Your cooling system will be at various temperatures while running. The water exiting at your thermostat will be the hottest part and the water leaving the bottom radiator the coolest part. Once you turn a car off the coolant is no longer being pumped around the engine and cooling system. The temp sensor is usually mounted with the thermostat at the exit point of the engine. Since the water flow is no longer being pumped around the engine it is now only moving at the speed of convection. Now a much lower volume of water is being exposed to the same amount of hot engine surface area it absorbs more heat. So yes it is normal for a temp sensor to read hotter when turned off.

    A lot of modern cars have electric water pumps and fans with computer control to allow them to run after the car is switched off. Which is great until in the middle of the night for no reason at all your VW decides it will run the fans and flatten battery ruining your day.
     
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  8. jellybeans

    jellybeans Active Member

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    ib just said what i said in two sentences haha
     
  9. IB

    IB ?????

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    Which fan are you referring to? The mechanical fan? Or electric fan?
     
  10. beaver

    beaver southern zeds

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    Both undertrays and the fan shroud are important, the undertrays (splash guards) between the bottom of the bumper bar and the crossmember, and from the crossmember to the back of the engine should be in place, and the fan shroud.

    "My question relates to the fan. If turn off the car the fan immediately stops. When I turn the engine on again after a couple of minutes the fan starts again, but the temperature gauge on the dashboard then shows the meter almost al the way in the hot area. It slowly then goes down again while driving. Is this normal?"

    Yes that is normal, it means that the electrict fan is doing its job, the overheating cause(not normal) is what you want to find, and that could be quite a few things.... ie, radiator fins clogged with crap, cooliant needs replacing, radiator and system needs flushing, engine problem, ect.
     
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  11. jellybeans

    jellybeans Active Member

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    In my long winded reply i did mean to mention dirty radiator but got sidetracked .
    Isn't the Netherlands known for flowers and therefore insects.
    insects seem to be the main cause of radiator blockage in my cars.
     
  12. Martin Williams

    Martin Williams Well-Known Member

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    Is the engine standard, or has it been upgraded, bigger turbos etc? if so what radiator do you have? In my experience of racing these cars, the original OEM fan did the best job of controlling water temperatures.
     
  13. rob260

    rob260 Moderator Staff Member

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    If the Electric auxiliary fan is coming on with ignition it is because the coolant temperature is over 105* Celsius.

    Shroud and trays etc improve efficiency but their absence alone will NOT cause the car to overheat.

    Given your symptoms I would suggest either cleaning or replacing the radiator, or replacing the fan clutch. Or both.
     
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  14. beaver

    beaver southern zeds

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    The ac condenser is in front of the radiator, that should be solid with road crap because you dont have the front splash shield, clean that up along the radiator.
     
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  15. TWIN TERROR

    TWIN TERROR Well-Known Member

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    You could easily make a new under tray out of tin or even a thin ply wood if need be.
     
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  16. jellybeans

    jellybeans Active Member

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    aluminium is so easy to work. I've been making a lot of parts with wood working tools mainly. love plywood too
     
  17. beaver

    beaver southern zeds

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    I think we have a winner...........
    [​IMG]
     
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  18. Niek

    Niek New Member

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    Hi Jellybeans.
    Thanks for your comprehensive reply. The Splash guard might be part of the cause, however when then slowing down it still struggles to come back to exactly in the middle (the gage). Problem with replacing the splash guard is that this bumper was build by the previous owner. The bottom part is from a Toyota Supra and the top part original. So likely an OEM splash guard won't fit. In any case the radiator might be clogged so definitely look into that. As said, it's not a huge peek (anymore) after the thermostat was replaced. But it's not exactly in the middle either....
     
  19. Niek

    Niek New Member

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    Hi Martin. The engine is standard and the turbo's as well (even standard pressure bar). Just some chip tuning was done by the previous owner.
     

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