525 M50 Fan blade question

[David P]

Hi all
First post here although the board has been a mine of information over the last year. I have done so much of the stuff talked about like capacitors in instrument console,heater matrix etc. I could not have kept this car on the road without this board and Brunos site

Over the last month or so I have been overhauling the cooling system on my 1991e34 525 M50. Slight overheating on idle. Replaced radiator, it had a leak,new water pump old one had plastic impellor and changed thermostat. Still overheating on idle if heating is off

Fan seems not to pass the various tests, it seems to spin free when engine is hot so new coupling bought today.

Removed fan and when installing new one I noticed the old one was fitted to the back of the fan. The bentley manual, ETK and drawings on the box the new coupling came in all show it fitted to the front of the fan. Followed instructions and when refitted the fan was so close to the engine it would not rotate without hitting cooling pipes. Refitted with coupling on the back, rotates fine but fan spins faster when engine is cold !!! and freewheels when hot. Back to the ETK and found fan should have 11 blades mine has only 9 guess the wrong fan has been fitted in the past and maybe because of different design of center hub size means the viscous clutch is to far back from the radiator to get enough heat to tighten up

Can any body confirm this. I will get a new fan anyway .Maybe others with cooling problems should check the position of the coupling on the fan ie front or back mounting

Can anybody with M50 engine confirm the number of fan blades ( No A/C )

Dave

e34 525 1991 manual (UK)

__________________

[Jose]

I counted 11 too before removing my fan and sending it to the bin.
You should have got rid of the visco fan and fitted an electro fan, much better/faster cooling and easier reving engine. The cheapest mod to free a bit of power.

[David P]

Jose
Thanks for the info. Does removing fan blades really improve power how less weight air resistance ?
Where do you mount electric fan ?
Dave

[Jose]

I mounted the fan on the engine side on to the radiator with selfmade brackets. The BMW fan is a constant rotating thing which when fully rotating can cause up to 4% power loss, especially when you' ve been in heavy traffic , the engine needs to make a very noticable effort to get up in revs. With a electric fan this problem is history, plus the coolant temperature is always constant. Your radiator has an opening on the right side to fit an temp sensor. Mine operates from 92-86. I' ve used a BEHR sensor.