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Removing the Viscous Fan?

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  • Removing the Viscous Fan?

    Has anyone done this?

    A viscous fan was quite old fashioned even when the car was new? Also surprised the S54 has one too.

    I have put a new fan clutch on mine just recently.

    To some degree if it ain't broke, but I was just wondering...

    However, the fan can be quite noisy and surely must add extra inertia to the engine as it's directly connected to the crankshaft.

    I think there are supplementary electric fans? Its not uncommon to have one large electric fan and then afterun fans.

    This then puts more load on the alternator and in term that takes some power to drive, but in general I was thinking a thermostatic electric fan might be more efficient?

    Anyway, just got me thinking!

  • #2
    As above, my car has not had a viscous fan on for years. A lower temp thermoswitch in the radiator itself will activate the from A/C "auxillary" fan at a more reasonable temperature (about 3/4 on the gauge), but this would only happen in hot summer days. If there is a concern just put the blowers on hot to drag heat off, but also as above the car really doesn't need that big fan hanging off the end.

    Just FYI, the stock temp sensor leaves the aux fan off until it's nearly in the red! which is why many people think it's just for the A/C.

    I actually put a manual switch on my car using a standard Z3 front/rear fog switch assembly (front fog will activate the fan on a simple circuit), so I can manually override and switch it on earlier or leave it to come on automatically.

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    • #3
      Thanks, did either of you notice any difference to the way the engine revs?

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      • #4
        Thanks, might try it out at some point. I have a new water pump to fit at some point as preventative maintenance so maybe when I’m replacing the coolant I might also try the lower temp switch and with/without the fan.

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        • #5
          Also removed Fan several years ago and fitted lower temp sensor - no issues experienced - also improves access to front of engine for belts / vanos.

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          • #6
            After having seen this mod done on the Wheeler Dealers episode on their S52 it has me wondering if this is worth doing on the S50.

            There was talk on the show of the fan blades connecting with the shroud and effectively detonating and causing significant damage.... is this an S52 issue or does this happen on the S50 also - and if so, how commonplace is this problem?

            I'm in two minds about the whole thing - on the show they showed not only fitting the different rad switch, but also a different water pump/pulley & belt - which sounds great but then I wonder in future if it goes into a garage and they don't know about this mod they might go fitting the wrong parts and cause an issue in the future (for me or a future owner).

            So... is leaving the viscous fan in place just asking for trouble - is it a time bomb waiting to go off and cause a major issue, or is this an overblown issue that doesn't affect the S50, or never really happens...?

            Interested to hear opinions / battle scars!
            ----------------
            David
            1999 M Coupe (S50)
            >>Read my journal here<<
            2005 Smart Roadster-Coupe Brabus
            2022 Range Rover Evoque PHEV

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            • #7
              Nothing overtly wrong with the viscous fan, but I suggest you check yours for play and do a spin test etc.

              If you fit a new viscous fan clutch and check the fan blades themselves for damage then I don't think you would have much to worry about.

              I fitted a new fan clutch as mine was on it's way out.

              When the fan is off and belts off it's worth checking for play in the waterpump.

              My waterpump was fine but i have a new pump to put on in the near future as preventative maintenance.

              The reason I'm considering dropping mine is that I hate the noise at idle and feel it must add a bit of drag to the engine and also put a bit of extra strain on the waterpump bearing.

              Another good preventative thing is to replace all of the auxiliary belt tensioners and belts if not done for some time.
              Last edited by urquattrogus; 27-01-2021, 11:10 AM.

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              • #8
                Not on the MC but have done this on 4x4s.....changed for an electric fan on a switch for deep water crossings. It stops the blades being smashed by the water resistance.

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                • #9
                  I think the S50B32 water pump is a much stronger unit than the S52 version and as such we don't have the same issues with the viscous fan as American owners. I have seen cars with the fan removed and it looks really odd and personally prefer good cooling over 1-2 bhp and a bit of fan noise - each to their own.

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                  • #10
                    That's reassuring to hear. I would have thought if the S50 fan had the same issues this forum would be full of horror stories, but it's not. I guess it's one to monitor but I think I'll leave as-is.
                    I also prefer the idea of additional cooling and can't help thinking that BMW would not have fitted this fan if they didn't think it was needed....
                    ----------------
                    David
                    1999 M Coupe (S50)
                    >>Read my journal here<<
                    2005 Smart Roadster-Coupe Brabus
                    2022 Range Rover Evoque PHEV

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                    • #11
                      I think the S52 has a crappy plastic T Stat housing too whereas the S50 at least has an alloy one from memory.

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                      • #12
                        Originally posted by urquattrogus View Post
                        I think the S52 has a crappy plastic T Stat housing too whereas the S50 at least has an alloy one from memory.

                        Very different set up on the US S52 and I think it may even have a bigger water radiator as they don't have a oil cooler like the S50 and S54

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                        • #13
                          Left my viscous fan off last year after doing the Vanos.
                          Checked the engine temp & electric fan cuts in just past normal (just before the second white line) then drags temp back to normal before cutting out. I figured this was fine & never changed the rad temp switch, maybe mine had already been done?
                          Difference in noise levels is quite dramatic on my car. it was like removing a small jet engine from under the bonnet
                          I have thought about putting back the shroud but not got round to it, quite like the extra access at the front of the engine.
                          I think that if the car was used for more than just cruising around (trackdays etc) I may have kept the viscous unit as a 'belt & braces' option.

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