BMW 325 CI e46 2001 Fan noise when accelerating

[Dannyboy325]

Hi All
My above mentioned car seems to make a loud fan noise when the revs go above 3500 when accelerating. It only happens when the temp gauge is in the middle, and it only starts after about 5min since the temp was in the middle. It's an auto, has about 168,000kms on the clock, and i drive mostly in heavy traffic. Can someone please advise if this is normal, or if something is wrong?

 

[ChrisBrand]

Have a look at your Water Pump. Could be on its way out due to bearing wear

 

[Blue Shirt]

Your car has an engine-driven fan with a viscous clutch, which is supposed to only lock up when the engine is at operating temps. This action causes the fan to work hard when the engine is hot, in order to draw more cooling air through the radiator. At revs above 4000 rpm, the clutch will release again to avoid damage to the fan.

If the sound you hear is a turbine-like fan noise, it seems to be normal. If there is a metallic noise, something is wrong.

All of the above assumes that your viscous fan is actually working, it is a known weak point on the E46 and must be periodically checked and replaced if necessary.

An easy way to check is to feel th stiffness with which the fan can be rotated by hand if the engine is at operating temps and turned off.

 

[jhbhc]

Your car has an engine-driven fan with a viscous clutch, which is supposed to only lock up when the engine is at operating temps. This action causes the fan to work hard when the engine is hot, in order to draw more cooling air through the radiator. At revs above 4000 rpm, the clutch will release again to avoid damage to the fan.

If the sound you hear is a turbine-like fan noise, it seems to be normal. If there is a metallic noise, something is wrong.

All of the above assumes that your viscous fan is actually working, it is a known weak point on the E46 and must be periodically checked and replaced if necessary.

An easy way to check is to feel th stiffness with which the fan can be rotated by hand if the engine is at operating temps and turned off.

Perfect explanation @Blue Shirt

 

[Waseem 333i]

Research hidden obc menu to see coolant temps. Press and hold left button on the cluster until you see a menu pop up. Then use the button to scroll through the menu. Go to option 19 then wait. When it changes and says on press and hold again. Then scroll to menu 7 and wait. Coolant temp should display on top left. I am not sure on the petrol car what values you should get so research that. On diesel its around 91 degrees. If you getting over 100 degrees then inspect your cooling system or do a flush.

The noise you are getting is the viscous fan locking up which is normal for that to happen especially with the current heat we are having. Its good to learn the temps from the obc to pick up problems before they get really bad.

 

[Dannyboy325]

Your car has an engine-driven fan with a viscous clutch, which is supposed to only lock up when the engine is at operating temps. This action causes the fan to work hard when the engine is hot, in order to draw more cooling air through the radiator. At revs above 4000 rpm, the clutch will release again to avoid damage to the fan.

If the sound you hear is a turbine-like fan noise, it seems to be normal. If there is a metallic noise, something is wrong.

All of the above assumes that your viscous fan is actually working, it is a known weak point on the E46 and must be periodically checked and replaced if necessary.

An easy way to check is to feel th stiffness with which the fan can be rotated by hand if the engine is at operating temps and turned off.

Thanks for the response. I checked the fan when the engine is off, and it can be spinned, but it stops immediately when I stop spinning it.
So if i understand correctly, the clutch locks up when going past 4000rpm, and that is the noise I am hearing? Or is the noise from when it unlocks?

 

[Tinuva]

You could consider an Electric Fan Conversion / Viscous Delete. Just make sure you understand the differences ect.

 

[JayDrft]

As blue shirt said....its meant to run free at idle and low RPM although it runs with the engine, it will be very easy to stop it will idling...if you hold the fan blades and increase rpm gradually it will eventually pull lose as it locks up, but it can be held back...so in short it grips when it needs to, and releases if it encounters any resistance....

If its making a noise at higher RPM, it means its locking up, and it doesnt have the slip that it is allowed to have...this is an indication the viscous clutch unit is not operating as it should...

Im pretty sure Goldwagen stock these units, just a simple replace, but remember it is a left hand thread to get loose...not the conventional right hand thread that we use to...so loosens oppposite direction.

Hope this helps. Failing remedy, the alternative is a electric fan conversion...

 

[Blue Shirt]

Your car has an engine-driven fan with a viscous clutch, which is supposed to only lock up when the engine is at operating temps. This action causes the fan to work hard when the engine is hot, in order to draw more cooling air through the radiator. At revs above 4000 rpm, the clutch will release again to avoid damage to the fan.

If the sound you hear is a turbine-like fan noise, it seems to be normal. If there is a metallic noise, something is wrong.

All of the above assumes that your viscous fan is actually working, it is a known weak point on the E46 and must be periodically checked and replaced if necessary.

An easy way to check is to feel th stiffness with which the fan can be rotated by hand if the engine is at operating temps and turned off.

Thanks for the response. I checked the fan when the engine is off, and it can be spinned, but it stops immediately when I stop spinning it.
So if i understand correctly, the clutch locks up when going past 4000rpm, and that is the noise I am hearing? Or is the noise from when it unlocks?

The viscous clutch is supposed to lock up at engine speeds from about 1500-4000 rpm if the engine is at operating temps (>90°C). It will start disengaging at higher engine speeds to prevent damage to the fan.

The noise that you hear is simply the fan pushing a lot of air when it locks up. Generally, if you can hear the fan operating up to 4000 rpm, the viscous clutch is working normally. If you still hear the turbine noise at 5000 rpm, the clutch is stuck and should be replaced.

However, they are know to fail, and if things go quiet, your car could overheat which is lot more expensive than replacing the viscous clutch. Goldwagen sells quality replacement units and they are not too difficult to replace. The big 32mm nut on the waterpump pulley has left-hand thread and you must devise a way to counter-hold the pulley, I normally jam a big flat screwdriver between the pulley nuts which allows the big nut to be unscrewed.

 

[AdiS]

My advice is to replace the fan blade at the same time as the viscous clutch. A Bmw original is not too expensive, and the reason you want to do this is because the plastic gets brittle with age and if it breaks it usually takes out the radiator and bonnet at the same time.

This is assuming your issue is a seized viscous clutch as has been suggested above (it probably is).




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