E39 540i Loud Engine/Fan Noise

[amunsey]

I finally convinced my dad to pass down his 2002 BMW 540i to me. The only thing that has been driving me crazy about it since I started driving it is the loud fan noise from the engine under acceleration. I haven't been able to verify it is the fan but it sounds like it would be. It sounds almost like a loud vacuum roar, and I dont think it is supposed to sounds that way. I can barely hear the V8 under all that noise. I have heard different causes of the noise such as a bad fan clutch and other things like that. I was wondering if anybody else has experienced this and what they found the problem was.

[edjack]

Did you check the fan clutch? If it is frozen, you best replace it pronto, or the blades will break off and wreak havoc under the hood. They may also put dents in the hood.

[amunsey]

This is probably a stupid question but how do I check that the fan clutch is bad? Some people have said if it is bad, you can stop the blade with your hand but I dont want to try that incase it is working properly haha.

[larrym3711]

When the fan clutch is "cold" it will turn with some resistance (using your hand...engine off...of course!). Then...after the engine heats up fully....it may be harder to turn indicating the fan clutch is "starting to engage" the fan assy. The test referred to is to take a roll of newspaper (many pages...or use a magazine) and push it slowly to the fan portion of the clutch assy....it should stop the fan easily. If it does not....the clutch may be "locked up"...and the noise you hear is the FAILURE TO DISENGAGE the fan when it should. It CERTAINLY should not spin very fast (and loud...of course!) when the engine is running at a high rpm. If it does...you are in serious danger of the fan exploding and having some SERIOUS damage to the hoses, shroud, and possibly the hood itself....that means many $$$$$$ to get it fixed!

larrym3711
2001 540iA Sport

[amunsey]

Okay so if it is a bad fan clutch, the fan will not stop when the newspaper is pushed into it? I just tested it and the fan did not stop when I used the rolled up newspaper.

[ElleShooTiger]

Try it with the engine off, it should turn by hand with some slight resistance. If its locked solid, then the clutch is shot.

Usually, if you raise the rpms, the fan will roar louder and louder and then it disengages around 3k or 4k rpms. If it gets louder and louder after those rpms, then it is likely locked up and must be replaced ASAP.

Be sure to get a BMW or Behr fan clutch!!! Do not even think about saving money on an aftermarket clutch, many of them are chinese crap and will cause more problems than the money you save.

[larrym3711]

+1 on OEM or BEHR fan clutch. Do NOT buy a bargain fan clutch.....you will pay dearly later! Check the fan too...they crack and then fail.

larrym3711
2001 540iA Sport

[amunsey]

It seems to be spinning fine when the engine is off. I might go ahead and replace it anyway since the part isn't that expensive and hopefully the loud fan noise will go away.

[525I ALLAN E39]

I have the same issue with my 2002 525i. it started two days ago. The sounds seems to be following the engine RPMs no matter what. at highway speeds im terrified to even step on the gas. even at 3k and 4k rpms it keeps pace with the engine.

[amunsey]

Mine does it unless I accelerate fast or until I reach something above 50mph. Its driving me crazy. Im going to have the fan clutch replaced this weekend and hopefully the noise will cease.

[larrym3711]

Hey! All of you with excessive fan noise...get that fan clutch replaced NOW!!!! I can't find the words to tell you the priority to get that change done right now. If you don't your financial exposure is just ridiculous!! Don't drive it AT ALL!! Fix it or pay a very high penalty for many parts and possible new hood!! Please !!! Heed this warning!!!!!

larrym3711
2001 540iA Sport

[Killacam3466]

Hi : I have the same noise on my 540i and I replace electric fan & clutch on radiator fan and I still have that loud blowing noise !! So I'm right back where I started

[gmak]

Could it maybe be the auxilliary fan on the front of the rad that comes on with air conditioning. I've heard that sometimes they sound like a plane passing by.

[dannyzabolotny]

The aux fan does make a ton of noise, but the fan clutches sieze pretty often on these cars, especially as they get older. If you neglect to replace it, your fan will spin too fast and the blades will shatter off and impale your hood and hoses. The blades can cause some pretty serious damage, like denting your hood pretty badly from the inside.

100_0739.jpg

[RoundLightsRule]

It may have something to do with the hot summer weather too. My 540i fan is loud once shes warmed up. I here it mostly around town when there isn't much airflow, below 35mph. Im not 100% on this but I believe there is a sensor that monitors underhood airflow... when I take off from a stop and hear what sounds like a big rig fan from under my hood, if I keep it at 3-4Kish in second, the fan clutch releases after several seconds. I think this has to do with water pump flow as well. Im pretty positive the PO replaced the fan clutch since my hood clearly shows the tell tail signs of carnage...

[kmitch9311]

In my experience, any EXCESSIVE fan noise should be addressed. I've never noticed much noise from my mech fan, before or after replacing the fan clutch. But my Aux fan did sound like a jet engine, for a while I wrote it off as normal as a lot of people seem to report loud aux fans. Tuns out my fan clutch had died in the "disengaged" mode, so it still spun freely but you could stop it with one finger (or more intelligently a rolled newspaper). The mech fan wasn't providing enough airflow after warming up so the aux fan was attempting to compensate. After replacing the fan clutch my aux fan hasn't sounded like a jet once. and my KTMP's are consistently 5-8 degrees lower than before.

[Wellsn]

Hi : I have the same noise on my 540i and I replace electric fan & clutch on radiator fan and I still have that loud blowing noise !! So I'm right back where I started

Same! Both fans & clutch replaced Noise even louder! What on earth!? 540iT and now 2 years of ever increasing fan noise volume after replacing all of the above.
One thing I was told by a Porsche race car mechanic is that my fan is far too small for its shroud and that it cannot pull enough air thru (the hydro fan) could this be it? And how are so many of us getting fans that are too small if that is the case!? Any ideas appreciated! I love my 540 dad wagon and want it for another 165k Miles. Thanks!

[mattmar1]

which fan is the one causing the noise? the front of the radiator electric aux fan or the clutched fan behind the rad? which brand clutch did you use when replacing it?

[Wellsn]

Hey it’s is coming from the hydraulic for sure and I asked my mechanic to use oem when replacing the clutch but I cannot confirm it myself. Can I? It really sounds bad and has only gotten louder for two years even after the new fan clutch. Ideas welcome.

- - - Updated - - -

Just realized something. Could it be my ambient temp sensor!? I remember that thing hanging down and bouncing around the front passenger wheel well back then and my guy just shoved it up toward the air damn so it would not hit the tire. I bet that is a partial culprit just not sure how. ?

[mattmar1]

ambient air temp sensor wont cause this. it your cluster temp is reading reasonably, the sensor is working well. its a common mod to relocate the sensor to avoid or after finding it hanging down.