E39 cooling fan running high

[E34-3.2]

Hi all,

A little bit puzzled at the moment. Just changed the radiator (due to leaks), fan, water pump and temperature sensors but for some reasons, the cooling fan is suddenly running super high. As I accelerate, it sounds like I have a 747 under the bonnet! It just does it randomly ( I think).

Any idea?

Cheers

[ian332isport]

Assuming this is the mechanical fan and not electric, it's probably a failing/failed viscous fan coupling.

They don't last forever and being removed and refitted has probably finished it off.

[E34-3.2]

ian332isport said:

Assuming this is the mechanical fan and not electric, it's probably a failing/failed viscous fan coupling.

They don't last forever and being removed and refitted has probably finished it off.

Thank you. We will investigate.

[danb79]

Time to replace your viscous clutch; stick with Mahle or Behr

Literally what I’ve bought today, plus there’s £10 off with WINTERSAVE

https://www.ebay.co.uk/itm/388592335789

[E34-3.2]

Great. I'll take the car to the mechanic on Friday. Thank you very much.
Can't let the old E39 die. Despite buying it a few year ago to feel a gap I haven't had the heart to sale it on. I love it!

[danb79]

E34-3.2 said:

Great. I'll take the car to the mechanic on Friday. Thank you very much.
Can't let the old E39 die. Despite buying it a few year ago to feel a gap I haven't had the heart to sale it on. I love it!

Good to hear

It’s a very easy DIY to do, but you need a long 32mm spanner and a good mallet - left handed thread FYI

If you can get some penetrating spray on the nut ASAP as that’ll make it easier to remove as they do like to get stuck on, more so if someone has whacked it on far too hard

[Triumph Man]

Yes, to echo above - don't go cheap - they roar.

If you've just changed the rad you would have to take the fan off, so it should come back off easily.

I used to hate taking the fan and that stupid shroud off! E34 was soooo much easier... I could change a rad in 20 mins!

[E34-3.2]

Triumph Man said:

Yes, to echo above - don't go cheap - they roar.

If you've just changed the rad you would have to take the fan off, so it should come back off easily.

I used to hate taking the fan and that stupid shroud off! E34 was soooo much easier... I could change a rad in 20 mins!

Had it done on my previous e34 if I remember rightly. Dam I miss that car!

[njw1]

Triumph Man said:

Yes, to echo above - don't go cheap - they roar.

They do more than roar if the viscous clutch seizes! On my previous 540i I had a fan literally explode, the mess was impressive, catastrophic almost! When it failed it also took out the top hose, radiator, header tank, fan shroud, both belts, punched a hole through the undertray, ripped the under bonnet sound deadening to shreds and dented the bonnet outwards...

...So yes, don't buy a cheap one!

[Triumph Man]

njw1 said:

Triumph Man said:

Yes, to echo above - don't go cheap - they roar.

They do more than roar if the viscous clutch seizes! On my previous 540i I had a fan literally explode, the mess was impressive, catastrophic almost! When it failed it also took out the top hose, radiator, header tank, fan shroud, both belts, punched a hole through the undertray, ripped the under bonnet sound deadening to shreds and dented the bonnet outwards...

...So yes, don't buy a cheap one!

Yes I've read stories about them exploding! Before I changed mine (a cheap one that roared - not fitted by me!), the aux fan also failed. We drove from Warminster to Cardiff in 33 degree heat, and everytime I ran the A/C the viscous fan roared so loudly I could hear it at motorway speeds... I turned the A/C off and rationed it! The fan still roared a bit as it was so hot outside. Then when I got back I changed the fan coupling for a decent one and a working electric Aux fan. I was lucky it didn't explode really.