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Thread: Testing for a bad Fan Clutch (Sachs and Behr)

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    Testing for a bad Fan Clutch (Sachs and Behr)

    Dorin (Doru) was kind enough to post up an excellent pdf on how to test for a bad fan clutch. He also pointed out there are two different test procedures for two different fan clutch manufacturers. The write-up below is for the Sachs fan clutch, and following that is Orkhan's (Orxan4ik) video for the Behr brand.
    (Since I can't copy/paste the pdf, I've copied the text into this post. Unfortunately I don't know who the author is and can't give them props. I'll try to find out.)


    Fan Clutch test
    First, lets discuss what the fan clutch does and why it is there. The fan clutch is just what the name says, it is a mechanism that will clutch the fan on and off depending on the need for more or less cooling air to flow thru the radiator. It is a thermostatically controlled device that when operating normally will vary the fan speed independently of the engine speed. When cruising down the road at freeway speeds, with outside temperature less then desert conditions, the fan should be merely be idling along, turning just fast enough to add a little air flow when needed, in this way the fan noise and drag on the engine is greatly reduced. When reducing speed, the fan clutch will sense higher temperatures thru the radiator and "clutch up" thereby increasing the fan speed to help maintain constant engine temperature. It may in fact, cycle as the temperature of the air thru the radiator changes depending on airflow. If the fan clutch operation is normal, when first starting the car, the fan clutch should "clutch up" and an increase in noise and airflow should be obvious. After about 60-90 seconds, the fan will un-clutch and the noise and airflow will drop. The fan will continue to turn but at a much reduced speed. As the engine warms and the thermostat opens to regulate the temperature, the air thru the radiator gets hotter and the clutch will sense this, thereby increasing the speed of the fan to maintain a normal operating temperature.
    First signs of trouble:
    A normal temperature indication at freeway speeds and an increasing temperature as the vehicle slows is one of the first indications of trouble. Many other things may give this indication but if the temperature seems to be stable at speeds but climbs in traffic or while stopped, this is a good indication that the fan clutch isn’t working correctly. As the temperature continues to climb, the auxiliary electric fan should start but may not provide enough air to keep the engine from overheating.
    Another sign of trouble is if the fan noise is high and never decreases after starting, and is there anytime the engine RPM is higher then idle, this means that the fan clutch is "frozen" and is not releasing. Although this will not result in immediately serious trouble, it will load the engine continually and gas MPG will be reduced. Load on the fan belt(s) will be higher and shorten the life of that component also.
    Fan modifications:


    It has been suggested that other models of BMW fans can be substituted to reduce the noise and load of the fan. This is
    NOT recommended! If the fan clutch is working properly, there should be no need to replace with a lesser fan. The noise and load of the fan should only be there when it is "clutched up" and the fan speed needed to keep that big V-12 cool. BMW designed it this way and it is never a good idea to alter the cooling system and in particular where alloy engines would be effected.

    Testing the fan clutch:

    If you have reason to suspect that the fan clutch is defective, here is the recommended procedure to verify the condition of the fan clutch.


    1. Start the car (cold) with the hood open and note if the fan is turning, increase the engine RPM and note if the fan turns faster and the noise increases, if it does, first good indication, if it
    does not increase speed/noise, clutch is bad and needs to be replaced. (Remember, this must be tested after the car has been off for and extended period, over night etc.)

    2. Leave engine running and note if the fan starts to slow down after 2-5 minutes, speed/noise should diminish and even raising the RPM, the fan should not make as much noise as when first starting, if it does slow, this is the second good indication. If speed/noise does not decrease, clutch may be "frozen" and should be replaced.

    3. Leave the engine idle and watch the temperature indicator. When normal operating temperature has been reached, some increase in fan speed/noise should be noted, in particular when the RPM is increased. If temperature is fairly stable and the fan noise/speed increases or cycles, third good indication. If temperature indication continues to increase, with no increase in fan noise/speed, clutch is defective and should be replaced.

    4. After the engine is at normal operating temperature or above, is the only time that the "rolled up newspaper" test that many people talk about should be performed! Take some newspaper and roll it up into a long narrow tube. Be carefull, keep hands and fingers away from the fan while performing this test! With the engine at full operating temperature and idling, take the rolled up paper and insert it on the back side of the fan and try to reach the hub of the fan avoiding the blades until close to the hub. Push the rolled paper at the fan increasing the friction to the hub area of the fan. If the fan can not be stopped easily this is the fourth good indication, if it can be stopped the clutch is defective and should be replaced. Again, this test can only be performed when the engine is at or above full operating temperature.

    Testing can be performed in any order but just make sure the conditions during testing are those that are specified for that specific test.

    Do not continue to operate the engine if the temperature continues to rise and certainly stop if the temperature approaches "redline".



    - Orkhan's video of the test for the Behr fan clutch.
    [ame]http://www.youtube.com/watch?v=46IREK0Mp_8&feature=player_embedded[/ame]

    Last edited by jamesdc4; 02-17-2012 at 03:42 PM.

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    Sweet. And if anybody's tests bad, I have one I will sell dirt cheap. With or without the fan if you need it. I just went with an electric fan
    I still own an e30, but life has picked up speed and I no longer frequent this forum or own my e39. Thanks for 7 years of help everyone!


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    Quote Originally Posted by champaign777 View Post
    fix link
    Thanks for the heads up.
    *fixed*

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    More info...

    Quote Originally Posted by Doru View Post
    Now that you ask me I am not sure. I nabbed it a long time ago, after I went through the "newspaper" posts about 3-4 years ago. Some conflincting statements in those threads made me look up how the fan clutch works. Then, after I digested a good pile of info from the net, on one of the forums I found this pdf, which made perfect sense to me, so I kept a copy.
    Now, I had a Behr fan clutch, which I exchanged this year with a Sachs clutch.
    The Behr clutch I believe performs slightly different than the Sachs:
    It does not move as much air, is silent, and actually the newspaper will stop the fan when the car is cold. Of course, mine failed and you could stop that clutch even with a hot engine...when I changed it.
    On the other hand, the Sachs clutch is engaged when cold and shreds the newspaper, then it releases the fan after about 60-80 seconds, just like the pdf. This is my new fan clutch. And it's loud, and it does everything that pdf states to a T.
    Also, I stumbled on numerous threads on numerous forums and subforums, where the Behr clutch seems not to perform even new - like not moving enough air, and being un-engaged most of the time. On our forum in the 3 series subforums you can check that too - they have threads about this issue. On the Festers 3 series, on the Roadfly forum, on Bimmerboard just to name a few. The 3 series folks had lots of trouble with the Behr clutch and they recommend the Sachs brand. On those foyums, on some 5 series subforums you can find the same info.

    All the best.

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    So the reference is to stay with SACHS if one can .. even though most parts sites list Behr as being the OEM for a 99 540.. still hunting for the sachs one to add to my monster parts list.

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    Ok, so the Sachs fan SHOULD stop from the newspaper if it's GOOD. Ok, I think I get it. The fan clutch is meant to provide variable RPMs on the fan. So, if the fan is stuck (always spinning, or can't be pushed), the clutch is not working, and the fan always spins at full blast. This now makes sense. The fan should have play. That means the clutch is not frozen.
    Last edited by OnTheFence; 02-17-2012 at 09:56 AM.

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    Quote Originally Posted by OnTheFence
    Ok, so the Sachs fan SHOULD stop from the newspaper if it's GOOD. Ok, I think I get it. The fan clutch is meant to provide variable RPMs on the fan. So, if the fan is stuck (always spinning, or can't be pushed), the clutch is not working, and the fan always spins at full blast. This now makes sense. The fan should have play. That means the clutch is not frozen.
    I believe if the clutch seizes, you get the BAM Effect...I still don't see how brand can make a difference in the testing procedure. *shrug*

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    Quote Originally Posted by OnTheFence
    Ok, so the Sachs fan SHOULD stop from the newspaper if it's GOOD. Ok, I think I get it. The fan clutch is meant to provide variable RPMs on the fan. So, if the fan is stuck (always spinning, or can't be pushed), the clutch is not working, and the fan always spins at full blast. This now makes sense. The fan should have play. That means the clutch is not frozen.
    Read a bit more carefully...the test he refers to is when the engine is COLD. Important to note the engine state when performing these tests. I've been instructed that the engine should be hot and the clutch should allow the fan to spin fast enough to keep the engine within proper operating temps, which means you should NOT be able to stop it from doing it's job (spinning).

    If we keep going back and forth with this, people are going to be so confused, they'll think we're a bunch of politicians...lol!

    Sent from my Transformer TF101 using BF.com

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    So what I'm getting is that brand really doesn't matter and:
    - if you are doing the test when the engine is cold, then you should be able to stop it
    - if you do the test after the engine has warmed up to operating temp, then you should not be able to stop it

    Is it better to do the test one way over the other? Does one way give you a more accurate result over the other?

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    Quote Originally Posted by splackavellie View Post
    So what I'm getting is that brand really doesn't matter and:
    - if you are doing the test when the engine is cold, then you should be able to stop it
    - if you do the test after the engine has warmed up to operating temp, then you should not be able to stop it

    Is it better to do the test one way over the other? Does one way give you a more accurate result over the other?
    Old post but I'm gonna respond anyway.

    YES to the first two questions, HOWEVER, I've read and been told that the "newspaper test" should only be performed when the engine is hot.

    I noticed in the video that he leaves his car running and then comes back to show that the fan clutch is still disengaged, which from my experience, would indicate a failed fan clutch. Why do I make this claim? Because by the time he returns to his running E39, it should have warmed up enough to have engaged the clutch. I finally noticed this on my M62TU because the friggin aux fan kept kicking in and sounded like an airplane under the hood (I guess BMW was originally an airplane engine manufacturer so it makes more sense). I discovered that I could stop my fan clutch when the engine was cold, warm or hotter than hell! A true indicator that you have a bad fan clutch, hence my lack of believing the video test is accurate. I'd like to see how his fan clutch operates after driving a few miles...

    Now my "new" fan clutch can be stopped when the engine is cold but as it warms up (only a couple minutes or so), the fan will chop your arm off. The other "tell" is that the aux fan almost NEVER kicks in anymore unless it's almost triple digits hot and I'm stuck in traffic. As a matter of fact, I just returned from a 1400 mile round trip to Vancouver, WA and back and the aux fan only kicked in once at a rest stop where the temp was 102 degrees.

    I swear that this is the most confusing topic (outside gas, oil or CAI) on this forum...
    Last edited by ViolinARC; 08-21-2012 at 01:24 AM.

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    Quote Originally Posted by 12CoolDude View Post
    I swear that this is the most confusing topic (outside gas, oil or CAI)
    ...or coolant system bleeding.

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    Quote Originally Posted by 12CoolDude View Post
    Old post but I'm gonna respond anyway.

    YES to the first two questions, HOWEVER, I've read and been told that the "newspaper test" should only be performed when the engine is hot.

    I noticed in the video that he leaves his car running and then comes back to show that the fan clutch is still disengaged, which from my experience, would indicate a failed fan clutch. Why do I make this claim? Because by the time he returns to his running E39, it should have warmed up enough to have engaged the clutch. I finally noticed this on my M62TU because the friggin aux fan kept kicking in and sounded like an airplane under the hood (I guess BMW was originally an airplane engine manufacturer so it makes more sense). I discovered that I could stop my fan clutch when the engine was cold, warm or hotter than hell! A true indicator that you have a bad fan clutch, hence my lack of believing the video test is accurate. I'd like to see how his fan clutch operates after driving a few miles...

    Now my "new" fan clutch can be stopped when the engine is cold but as it warms up (only a couple minutes or so), the fan will chop your arm off. The other "tell" is that the aux fan almost NEVER kicks in anymore unless it's almost triple digits hot and I'm stuck in traffic. As a matter of fact, I just returned from a 1400 mile round trip to Vancouver, WA and back and the aux fan only kicked in once at a rest stop where the temp was 102 degrees.

    I swear that this is the most confusing topic (outside gas, oil or CAI) on this forum...
    Pretty much the same story with my fan clutch.

    So is there really two ways the fan clutch can fail... by not engaging or by locking up? If so, then it sounds like you need to test it both ways to verify that its not locking up when the engine is cold (you should be able to stop it) AND that it is engaging when at operating temp (you should NOT be able to stop it). This might also explain why this is such a confusing topic.

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    Quote Originally Posted by jamesdc4 View Post
    4. After the engine is at normal operating temperature or above, is the only time that the "rolled up newspaper" test that many people talk about should be performed! Take some newspaper and roll it up into a long narrow tube. Be carefull, keep hands and fingers away from the fan while performing this test! With the engine at full operating temperature and idling, take the rolled up paper and insert it on the back side of the fan and try to reach the hub of the fan avoiding the blades until close to the hub. Push the rolled paper at the fan increasing the friction to the hub area of the fan. If the fan can not be stopped easily this is the fourth good indication, if it can be stopped the clutch is defective and should be replaced. Again, this test can only be performed when the engine is at or above full operating temperature.
    Quote Originally Posted by OnTheFence View Post
    Ok, so the Sachs fan SHOULD stop from the newspaper if it's GOOD. Ok, I think I get it. The fan clutch is meant to provide variable RPMs on the fan. So, if the fan is stuck (always spinning, or can't be pushed), the clutch is not working, and the fan always spins at full blast. This now makes sense. The fan should have play. That means the clutch is not frozen.

    Isn't this contradictory?

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    Quote Originally Posted by rcatank View Post
    Isn't this contradictory?
    Here is the best test of all:
    Do you have $90? If yes, just replace the F'ing thing.
    That's what I did. At some point, internet forum info is garbage.
    The fan clutch is one of those topics.
    You'll spend more time reading all the contradictory debate than it takes you to earn $90.

    Just replace it. Done.

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    Cool

    Quote Originally Posted by OnTheFence View Post
    Here is the best test of all:
    Do you have $90? If yes, just replace the F'ing thing.
    That's what I did. At some point, internet forum info is garbage.
    The fan clutch is one of those topics.
    You'll spend more time reading all the contradictory debate than it takes you to earn $90.

    Just replace it. Done.
    Thats not much of a test than a decision...

    What you suggested is what I did with my whole cooling system overhaul, forked up the $900 in pump/rad/thermostat/15 hoses total, all sensors, blah blah, blah....


    Anyway, I figured out its not the fan or the fan clutch. Both work fine. It was a F*ng $2 Fuse...

    gg...

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    Lol $2 fuse ftw.

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    I have the symptoms of a bad fan clutch. Could the fan lock up only when the engine is at operating temp and then run just fine when you start the car and for the first 10-15minutes?

    Sent from BF.com using my iPhone?

    Serious question, my car has been making this noise accelerating from a stop only once it's at operating temps. It sounds like what everyone describes as air being moved really fast, like a jet engine, this loud whirring noise. I have read a lot on this and im stumped.
    It runs great when I start it up and for the first 10-15 mins, never makes the noise, but once warmed up it does it at every stop and gets worse if I don't let the car cool down. I have one code for catalytic's but they aren't making any rattling noise yet and I don't think that's related.

    I would appreciate help from anyone who has delt with a similar issue, thanks.

    Update: I found the answer on bimmerfest, thanks anyways. If you have this issue http://www.bimmerfest.com/forums/sho...d.php?t=279763
    Last edited by E39 Sean 540ia; 10-12-2012 at 10:58 PM.

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    Major thread resurrection here, I know.

    I had overhauled the cooling system on my 530i, but foolishly used a URO Fan Clutch thinking that it couldn't possibly be that much worse, plus it was $45, which was less than half the price of the Sachs. Well, I installed it, and noted that it made quite a bit more noise than the original, which was Sachs. I thought it would quiet down after a while, but no such luck. I constantly feared that it was spinning way too fast and that it would tear the fan blades apart while I was passing someone on the highway. I did not have any other noticeable problem, but I knew something just wasn't right.

    So, today my 13-year-old son and I replaced the URO with the correct Sachs unit, and I am much happier. When I first start the car it is engaged, but after maybe 30 seconds it behaves as normal. Nice and quiet. No overheating or anything, and much less noise!!! I am much happier with the Sachs.

    Plus, there has been some concern about how to thread the new fan clutch onto the water pump. My son has found the correct way, and showed me. No more leather shoelaces, or what-not. I simply held the clutch in place with my two hands, and he turned the nut counter-clockwise with the thin 32mm wrench - voila - right on with the very first try. I was pretty sure that they weren't using leather shoelaces in the factory!

    I hope this helps someone


    - - - Updated - - -

    PS does anybody have any experience returning a fan clutch like this to a parts vendor (RockAuto in this case) because it just isn't right?

    Thanks

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    - URO parts: no need for me to comment, the forums have had enough of URO stuff.
    Sachs is the king.

    - The Fan Clutch shoe lace/poultry cord trick: useful when one is working alone. However, when you have an assistant, then no need for shoe lace/poultry cord trick. I usually put some antiseize on the fan clutch so the next removal is much easier.

  21. #21
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    Hi edbikerii,

    Sorry to hear about your experience with our fan clutch. This is probably our best selling fan clutch and warranties are virtually nil. If you return it through RockAuto we will make sure you get the credit back as well as take a look at it to see what happened in this case.

    If there's anything else you need, please let us know.
    Last edited by URO Parts; 08-05-2015 at 08:12 PM.

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    Stop the misinformation.

    I have to add my $0.02 here, even though this is an old and beaten topic. Has anyone ever tested their NEW fan clutch with the rolled up newspaper. I have, on my 528i where I replaced it because I could stop it with my hand. Well guess what? You can stop the fan when the engine is at operating temperature as well. When the engine is cold, I can spin the fan and it only goes a quarter turn or so. See below as to why.

    - - - Updated - - -

    There are two types of fan clutches: Thermal and non-thermal. Apparently, the thermal have that spiral bi-metal thermostatic coil in the middle. This reacts to the UNDER HOOD temperatures and acts accordingly. by tightening more and more on the rotating shaft as temperature rises. I guess at higher temperatures, one couldn't stop this fan with a newspaper. At high enough speeds, the attached fan is probably at risk of 'exploding'.

    A non-thermal clutch doesn't are about temperature, but rather the speed of the shaft of the water pump. The only thing it does is limit the top end speed and thereby avoiding the explosion of the fan. This type of clutch would always fail the rolled up newspaper test.





    How to Detect a Faulty Fan Clutch (Note the absence of a rolled up newspaper.)
    • Fan spins excessively when engine is stopped.
    • Poor A/C performance at idle or low vehicle speeds.
    • Fan speed does not increase when engine is hot.
    • Fan speed does not increase until engine is excessively hot.
    • Fan blade tip moves more than 1/4” front to back.
    • Fan turns roughly or does not turn at all.
    • Excessive fan noise at all speeds due to failed bearing.
    • Vibration that increases with engine speed.

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    Great post. My BEHR clutch seems to be non-thermal (metal strip), and is pretty loud. The one I removed had a coil.

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