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Thread: Viscous clutch fan delete ?

  1. #26
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    Quote Originally Posted by bdiefAZ View Post



    Another question:


    The aux fan on the Z3 is triggered either by the AC system running or a temperature switch in the radiator and has 2 speeds. Would it be possible to run a larger fan as a puller (more efficient) with this dual purpose setup and use existing wiring from the aux fan? Is there something that I am missing?

    Sorry for the repeated/re worded question, I am not the electrical expert!
    No, you're not missing anything. You can swap from the pusher aux fan to a puller fan using the existing wiring and resistor. A lower temp radiator thermal switch will help mitigate to viscous fan delete. If you want to run both fans at once you should use a relay to power the second fan. Just replacing the viscous fan with a puller fan will not be nearly as effective without also providing a tightly sealed shroud--the bare fan will create a fan shaped cool zone in the radiator immediately ahead of the fan, the fan/shroud combination creates a low pressure zone across the entire back side of the radiator, resulting in the entire surface of the radiator providing cooling. Zionsville makes a shroud paired with a Spal puller (and a radiator) for this purpose.

  2. #27
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    If the viscous fan gets replaced with an electric puller fan for backup, how would you know if either of the two fans ever failed individually? Having the extra backup fan greatly reduces the risk of a fatal overtemp situation, but they both could still fail unexpectantly at some point.

    Does the oem pusher fan produce an instrument panel warning if it fails? If not, is there a means, other than an overtemp condition to monitoring its normal operation like a green light under the dash?

    Many poster’s concern about doing the viscous clutch removal alone is the chance that they could damage the engine if the aux fan alone ever fails.

    How do all the other models running a single electric fan monitor for normal operation and warn the driver of a fan failure before its too late? As others have posted, going to a single fan on our Z3s should be no less risky than any other vehicle running a single fan.

  3. #28
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    I have written hundreds of posts on this very subject, and really don't feel like visiting it again. But, stupid ideas seem to not die.

    The E39 / E46 do have a fan temp sensor. It's at the lower hose rather than stuck in some asinine spot in the tank like ours. And it's a true sensor rather than a switch. No magic, the computer watches the radiator outlet temp and adjusts fan speed to suit.

    Pusher fans are not better or worse than puller. The shroud makes 100 of the difference in fan effectiveness. You will not get as effective a shroud between the radiator and engine as the factory front shroud. I don't care how many gazillion CFM your fan claims, without a proper shroud it won't move as much air through the matrix.

    Thinking that a fan failure means immediate catastrophic engine damage is false. As long as there is liquid in the head, not air, not steam, then the engine will be fine. As long as you run a proper coolant mix and the proper cap (2.0 bar, those who think a 1.2 bar is better need to go back to riding bicycles), the gauge will give you plenty of warning. Yes, the BMW engineers did know what they were doing. Now, if you run pure water, a 1.2 cap, and ignore the gauge (and the steam clouds), then the engine damage is on you, not the fan.


    /.randy

  4. #29
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    Thanks for your patience.

    I did a viscous clutch fan delete only and will leave it at that. I’d rather deal with a temperature rise than a blown viscous fan.

  5. #30
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    It has been a while and my memory is not great, but I think I remember someone telling me that fan/clutch failure was not an issue for M52B25TU equipped Z3s. Is this correct?

    Stubbornness is a virtue....

  6. #31
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    I wasn't worried about deleting the viscous fan in my '02 540i in the winter. But when I was stuck in stop and go traffic, in August, with the AC on, I started watching the KTMPs. The electric fan did fine and held it's own in all cases. I might install a back-up sometime, but I've been driving it this way for 2 years now with no problems. SO much nicer without the sound of the viscous fan. Prob more fuel efficient too.

  7. #32
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    Quote Originally Posted by z3forlife View Post
    You would likely overload the circuit trying to run two fans in the same circuit. There is a thread that discusses adding a additional temp sensor in the return hose from the block
    The fan upgrade consists of removing mechanical belt driven fan and electric auxiliary fan. Once both are removed, a larger electric puller is installed in the place of the mechanical fan utilizing the auxiliary fan's wiring / circuit

    Here is a post from the e46 forum that illustrates the fans:

    https://forum.e46fanatics.com/showthread.php?t=884299
    Last edited by bdiefAZ; 12-06-2018 at 01:54 AM.
    Regards,

    Brian
    Cave Creek, AZ

  8. #33
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    Quote Originally Posted by blkwpnz View Post
    It has been a while and my memory is not great, but I think I remember someone telling me that fan/clutch failure was not an issue for M52B25TU equipped Z3s. Is this correct?
    That's incorrect. All BMW's equipped with a plastic clutch fan are prone to failure.
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  9. #34
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    One datapoint about the clutch fan: When I asked my mechanic about "parasitic drag" from the clutch fan, he said "Lean in there and spin it with your finger." (The car wasn't running, BTW.) The clutch - if working properly and isn't failed and seized up or something - allows the fan to spin quite freely when disengaged. Whatever the complaints about the clutch fan, the idea of it burdening the engine is probably mistaken.

  10. #35
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    Agree. Almost all of the horsepower would be applied at the wheels. Air conditioning would be next. Other accessories would be minimal. I seriously doubt that dyno run comparisons with and without these parasitic accessories would detect any difference. I removed my viscous clutch fan to eliminate any future risk of a damaging failure. A side benefit is listening to a fan free engine running with the hood popped.
    Last edited by Tigershark48; 12-06-2018 at 09:54 AM.

  11. #36
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    Quote Originally Posted by bdiefAZ View Post
    The fan upgrade consists of removing mechanical belt driven fan and electric auxiliary fan. Once both are removed, a larger electric puller is installed in the place of the mechanical fan utilizing the auxiliary fan's wiring / circuit

    Here is a post from the e46 forum that illustrates the fans:

    https://forum.e46fanatics.com/showthread.php?t=884299
    Thats removing 1 electric fan and 1 mechanical fan to install a different electric fan

    I dont know why you are trying to reinvent the wheel here. The e46 fan wont fit as I already mentioned and it would draw too much current for the wiring as others have mentioned. And e46 fans were PWM controlled, Z3s have no way to ouput a PWM signal wire. The e46 electric fan conversion is not possible on a Z3.

    If you are this worried just install a new fan clutch... In AZ a fan delete will creep above tdc in some circumstances. No way around that in extremely low humidity and high heat situations

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  12. #37
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    Let me get this straight...

    Some here have commented about removing the front fan and adding an electric fan and others appear to claim the front fan can simply be removed.

    I can remove the fan that is attached to the water pump, leave its shroud in place, button up the car and forget about it? No need for an extra electric fan?

  13. #38
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    Correct. Unless you do commuting with lots of stop and go in super hot weather, the viscous clutch fan (water pump attachment) can be eliminated and you’re done. You still have an electric fan in front of the radiator that’s thermostatically controlled. Same thing I have on both of my toyotas and all the ones I’ve ever owned. Same as my motorcycle as well. Having two fans and eliminating one makes owners uneasy, but having two fans is actually more uncommon than one single fan.
    Last edited by Tigershark48; 12-07-2018 at 09:48 AM.

  14. #39
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  15. #40
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    Quote Originally Posted by streetmaster View Post
    Yeah man, i've replaced my pump, along with a new aluminum pulley, and the stock rad, by chance do you recall about how far the fan hub is from the mounting point of the rad, hopefully its around 2.5" considering you're new rad is either thinner or thicker than oem. Im sure ill be golden, yeah that fan drag of the clutch fan drove me nuts lol.
    Mishimoto website says the fan is 2.87” thick. And yes the rad I have is thicker than oem. I had to bend the mounting bracket that comes with the kit so there could be more clearance between the water pump pulley and the fan hub. As it sits now there is less a 1/4” gap.
    And here is where I mounted the relay.



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  16. #41
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    I recently left mine out. No problems yet. I'll consider puttin in the lower temp sensor if I ever see the gauge creep. I don't get into a lot of traffic.

    As to those saying a fan failure will leave me stranded. What??? No, I'll wait for the car to cool and the traffic to leave and then get back on the road. No problemo. I'm much more likely to be stranded because the plastic fan threw a blade trough my hood and is now unbalanced.

  17. #42
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    The temp gauge is buffered and doesn't reflect changes that would allow you to react to an overheat condition. There's a reason why a fan delete encompasses many steps to be effective. I would trust a mechanical fan more than I would trust watching my temp gauge. Then again, I'm an old fart with poor vision
    Tony
    "You can't sign away negligence."

  18. #43
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    Where do you find the lower temp switch for an M52tu. I can't find that info anywhere on any of these threads

  19. #44
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    Quote Originally Posted by ihm96 View Post
    Where do you find the lower temp switch for an M52tu. I can't find that info anywhere on any of these threads
    Here: https://www.bimmerforums.com/forum/s...S52-fan-delete

  20. #45
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    Quote Originally Posted by newbimmerguy12 View Post
    I recently left mine out. No problems yet. I'll consider puttin in the lower temp sensor if I ever see the gauge creep. I don't get into a lot of traffic.

    As to those saying a fan failure will leave me stranded. What??? No, I'll wait for the car to cool and the traffic to leave and then get back on the road. No problemo. I'm much more likely to be stranded because the plastic fan threw a blade trough my hood and is now unbalanced.
    It's now late August and it's been a hot summer. Still no problems here.

  21. #46
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    I took my viscous fan out, but later bought a brand new one and installed it.

    Why?
    1) I wanted to try and avoid a catastrophic of the 20 year old plastic fan tearing up my hood, radiator, etc.
    2) I felt that the car was running hot, in stop and go traffic, on 90+ degree days. I used a Bluetooth adaptor to get a real temperature and saw temps that made me a little squeamish.

    My electric fan works and would be on.

    It just didn’t seem worth the little quieter sound to run the engine hotter than it had to be.

    So a new clutch and fan for me. I sleep well believing the fan wont explode, and the engine is as cool as I can make it.

    Greg
    Last edited by Tallyho322; 08-27-2019 at 09:58 PM. Reason: misspelled soemthing
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  22. #47
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    I've thought of doing the same thing, but don't know how long it would be until I'd stop trusting the new viscous fan. From what I've read, the fan explodes without a warning.
    Wayne

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  23. #48
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    Quote Originally Posted by Tallyho322 View Post
    I took my viscous fan out, but later bought a brand new one and installed it.

    Why?
    1) I wanted to try and avoid a catastrophic of the 20 year old plastic fan tearing up my hood, radiator, etc.
    2) I felt that the car was running hot, in stop and go traffic, on 90+ degree days. I used a Bluetooth adaptor to get a real temperature and saw temps that made me a little squeamish.

    My electric fan works and would be on.

    It just didn’t seem worth the little quieter sound to run the engine hotter than it had to be.

    So a new clutch and fan for me. I sleep well believing the fan wont explode, and the engine is as cool as I can make it.

    Greg
    I did exactly the same things for the same reasons. The original fan did not explode for 20 years. I suspect the new fan will last 5 to 10 years at which point I'll replace it again.

    In the heat of the summer in Georgia, the viscus clutch engages only after running at speed and sitting at idle for a few minutes or after being parked for a few minutes with the engine off.

    Yes, I can hear the fan when the clutch is engaged. No, that doesn't bother me. I take it as a warning not to run the engine at high revs until it stops - further reducing the possibility of a fan "explosion."

  24. #49
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    That would be the electric pusher fan in front of the radiator, not the viscous puller behind the radiator. The viscous fan is mechanically driven by the fan belt and will not run when the engine is off.

    The fan belt driven viscous fan behind the radiator is the one that owners are removing because it has a history of disintegrating.

    I was torn about deleting mine, since it only had 20k miles on it. The failures posted shows a big range of miles, so there’s no recommended replacement interval. The possibly of failure at any point and time convinced me to delete it.
    Last edited by Tigershark48; 08-29-2019 at 09:10 AM.
    You can’t have everything. Where would you put it?

  25. #50
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    I know the difference between the sound of the electric pusher fan and the viscous puller fan. The noise to which I refer is never heard when the engine is not running. Also its pitch is directly related to engine RPM.

    I suspect the weakness and subsequent failure of the viscous driven fan is related more to its age and its exposure to heat and chemicals (which causes it to become brittle) than to the miles it has been driven. Although the latter probably has some effect.

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