Do your engine fans run a lot?

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deutsch100

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#1
Just wondering if your guys' engine fan runs a lot? I have noticed that the last week or so, and it is running a lot (and it has only been between 75-80F), that I can hear the loud fan in the engine bay. This is really evident when I am stopped completely, then begin to accelerate...I hear this muffled, heavy fan "airy" sound opposed to the normal sweet and melodic tone of the engine. I asked my cousin who has a new 325i, and she says she hears the fan sometimes too. Never hear this in our Alpina, and never in the newly deceased X5 4.4i :-(

All fluids are fine in my 3er, the temp. gauge always shows perfect, and my car only has like 600 miles on it.

Suggestions/comments?? Danke Schön :)
 
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bmwrocks

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Mine sounds like it is roaring sometimes. Seems to do it if the car is left idling for any time. I asked and was told it is normal.

My X5 has never done it.
 
jrt67ss350

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What you are hearing is the fan clutch locking up in order to drive the belt driven fan at the same speed as the water pump pulley. It gets loud because BMW belt-driven fans move A LOT of air when the fan clutch is locked up. It should only really happen when the car has been idling for a little while since the fan clutch is thermostatically controlled. If you leave the car idling, or begin to accelerate, the clutch should unlock after the increased airflow cools down the radiator. If you are hearing the roaring constantly, then there is a problem with the fan clutch.
 
theBMWenthusiast

theBMWenthusiast

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Chesty Bonds said:
Yeah this is normal. My dad's 740il has truly astonishing fan noise on start-up and under acceleration. It should cut out once the air-flow is happening.
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hehe...ya when you start those 740's up they do make a lot of noise, i actually love hearing that noise when my dad is leaving and hear the engine roar! [rolleyes]
 
aNoodle

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jrt67ss350 said:
What you are hearing is the fan clutch locking up in order to drive the belt driven fan at the same speed as the water pump pulley. It gets loud because BMW belt-driven fans move A LOT of air when the fan clutch is locked up. It should only really happen when the car has been idling for a little while since the fan clutch is thermostatically controlled. If you leave the car idling, or begin to accelerate, the clutch should unlock after the increased airflow cools down the radiator. If you are hearing the roaring constantly, then there is a problem with the fan clutch.
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Interesting. The fan, or propeller, connected to the engine is of course on all the time. But I thought the other fan in front of the radiator was electric. I noticed on the new 5ers that there is no fan in front. I wonder if they located it behind the radiator or just get rid of it entirely?
 
MrElussive

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Interesting topic. I actually specifically recall how obxnociously loud my uncle's former 740iL (now has the 745Li) was when starting up. Definitely the loudest engine startup I've ever heard, lol. You hear the starter motor work and then all of a sudden "ROAR!!!!!!!!!!!!!!!!!" that noise was defeinitely MAD LOUD.
 
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jrt67ss350

jrt67ss350

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aNoodle said:
Interesting. The fan, or propeller, connected to the engine is of course on all the time. But I thought the other fan in front of the radiator was electric. I noticed on the new 5ers that there is no fan in front. I wonder if they located it behind the radiator or just get rid of it entirely?
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Yes, the belt-driven fan does run all the time, but it doesn't run at full capacity all the time. The fan has a clutch - when the clutch is not engaged (cooler air coming out of the back of the radiator) the fan turns at much less than engine speed since the disengaged clutch allows slippage. When the radiator temp heats up (like when idling in traffic), the fan clutch engages, and the fan turns at engine speed. This is when it makes all the noise. The electric fan is an auxilliary fan that is only engaged when either the A/C is turned on or when the coolant temp climbs to an excessively high level and isn't being cooled appropriately by the primary belt-driven fan.
 
jrt67ss350

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Yeah, the fan clutch will engage on startup after the car has been sitting for a while because of the design of the clutch. The clutch is a viscous coupling that uses a silicone-based fluid. When the car sits for a while, that silicone fluid drains to the bottom of the clutch housing. Then, when the car is started, this uneven distribution will make the fan run at engine speed until the silicone gets more evenly dispersed throughout the clutch. The clutch does not operate properly until the silicone fluid is evenly dispersed.
 
codex57

codex57

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MrElussive said:
Interesting topic. I actually specifically recall how obxnociously loud my uncle's former 740iL (now has the 745Li) was when starting up. Definitely the loudest engine startup I've ever heard, lol. You hear the starter motor work and then all of a sudden "ROAR!!!!!!!!!!!!!!!!!" that noise was defeinitely MAD LOUD.
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My neighbor has the previous gen 740i. It is loud I guess, but not nearly as loud as some SUVs. THeir Excursion is even louder. My old Jeep Cherokee was insanely loud too. I used to sneak out of the house in high school. I literally had to put the car in neutral and shove it half a block away before I dared start it. It was stock too.
 
MrElussive

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codex57 said:
My neighbor has the previous gen 740i. It is loud I guess, but not nearly as loud as some SUVs. THeir Excursion is even louder. My old Jeep Cherokee was insanely loud too. I used to sneak out of the house in high school. I literally had to put the car in neutral and shove it half a block away before I dared start it. It was stock too.
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Hahahaha, that's just like every teen high school movie lol.
 
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