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  • Radiator cooling fan

    I'd appreciiate some advice: My S54 M coupe is running at below normal operating temperature and I notice the radiator cooling fan is permanently engaged: has anyone had a similar problem (the fan is rotating at full speed as soon as the engine is switched on)?
    I suspect it may be the sensor that operates the fan but don't know where this is located. I've checked old threads but can't find anything.

    Thanks
    S54 M Coupe
    D5 Alpina Touring

  • #2
    If you mean the big fan on the end of the engine then that is always spinning. It is on a clutch though so that it only fully follows engine speed when it's hot, so at cold idle it may look to be spinning but you can easily stop it with your hand (or something more suitable lol).

    If you mean the smaller fan in front of the radiator, that's the air con fan and that will genereally cut in and out if you have the air con switched on.

    If the temp is always a little low then that will be the thermostat which controls the temp in the engine block.

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    • #3
      It's the big fan behind the radiator but it's spinning like a son of a gun, I'll try sticking something other than my finger in it but it's more than a gentle spin
      S54 M Coupe
      D5 Alpina Touring

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      • #4
        DONT STICK ANYTHING IN THE FAN!!!! ANY FAN!!!! if you wanna check the big fan thats on the front of the engine...it should rotate when the engine is off!!! as mentioned before the one on the front is A/C !

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        • #5
          Point taken. The large fan behind the radiator is still (not rotating) when the ignition is turned on but spins at a very fast rate when the engine is started, far too much in my opinion. The car used to run with the temperature a gauge bang in the middle, now it runs with the gauge left of centre and I think it's because the engine isn't getting properly warm by the fan's action. If I sit in traffic the gauge goes back to normal, hence I don't think it's the gauge but I suspect it's a switch sticking that operates the radiator cooling fan but I'm insure where this switch is

          Regards
          S54 M Coupe
          D5 Alpina Touring

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          • #6
            number 7 is temperature switch,
            http://www.realoem.com/bmw/showparts...09&hg=17&fg=05



            viscous fans are well known to fail aswell.

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            • #7
              Thanks Dave
              S54 M Coupe
              D5 Alpina Touring

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              • #8
                As said it will be a failed viscous coupling on the fan. As it gets hotter then the drive is increased. Sounds like yours is driving regardless of temp.

                Change it ASAP. Driving at high speed with the coupling failed can cause problems as the fan blades would be highly stressed spinning away and having to contend with the incoming air. They are a LH thread

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                • #9
                  One thing to remember is that the thermostat controls the engine temp and the water in the engine, the fan "over cooling" the radiator or just spinning round is unlikely to affect it too much IMO as the water shouldn't be flowing through the radiator until it's up to full temp (middle of the temp gauge), before this temp the thermostat is closed, so it sounds to me like the thermostat is stuck open a little? The moving viscous fan could well be a red herring.

                  Just clarify, the "big" fan is not in any way electrically switched or powered. One way to check if the fan is "locked" is to blip the throttle, they sound a fair bit louder than normal when they turn at engine speed. Or see how hard it is to turn with the engine off; it should spin fairly free (but not spin round on it's own, just move freely with your hand)
                  Last edited by c_w; 27-01-2011, 11:42 AM.

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                  • #10
                    A new temp guage and viscouse fan coupling should not set you back to much...should nail it...fit the temp guage first (non refundable) if it sorts it you should be able to return the coupling to the dealer,if it dos'nt youve got a spare temp valve..!

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