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TECHNICAL MOTOBRICK WRENCHING In Remembrance of Inge K. => The Motobrick Workshop => Topic started by: cefalu on May 22, 2011, 01:09:23 PM

Title: 1987 K75s radiator fan frozen
Post by: cefalu on May 22, 2011, 01:09:23 PM
Yup, as advertised it is frozen. A pretty typical failure as read. I just ordered a new motor from Euro Motor Electrics. What is the best way to access the motor / fan for replacement? I just did the 30K service yesterday which involved replacing the coolant so I am not  going to be happy if it involves draining the coolant!

Doug
Title: Re: 1987 K75s radiator fan frozen
Post by: frankenduck on May 22, 2011, 02:48:12 PM
It's kind of a tight fit but I've replaced fans before without draining the coolant.  Undo the 5mm bolt at the top middle of the radiator and tilt it forward.  Then remove the two 4mm countersunk Allen bolts at the bottom that hold the fan to the back of the radiator.
Title: Re: 1987 K75s radiator fan frozen
Post by: johnny on May 22, 2011, 06:44:34 PM
greetings cefalu...

i had a motor seize up after i degreased the bug at the quarter carwash... i didnt let it run long enough to work out all the degreaser n it sit for a week n it was locked the next time i rolled... im thinking gotts to get it hot n run that fan several times a year to keep it good...

anyway... i tried to free it up wit pb blaster but no go... so i did the swap exactly as frankenduck described and didnt lose any coolant... it was a very easy repair...

j o
Title: Re: 1987 K75s radiator fan frozen
Post by: cefalu on May 23, 2011, 10:53:37 AM
OK, that's good news, it looked really tight. I could hardly get my fingers in there to test the fan. The motor I ordered was processed for shipping Sunday night, so I should have it here by the weekend. I'll give an update when it's done.
Title: Re: 1987 K75s radiator fan frozen
Post by: cefalu on May 29, 2011, 12:15:27 PM
OK, I swapped out the motor yesterday. But I ended up draining the coolant and pretty much taking it all apart. Now that I know how it goes together I could probably do it with just the 3 screws. But not a big deal once you have done it a couple of times. My fan motor was frozen solid and both brush holders completely melted. No fixing that motor. I have attached a couple of pics. I mean really melted...The fan motor swap was easy. You do have to swedge on some M/F spade connectors to the old fan motor feed, but that's as technical as it gets. The original feeds were soldered, and the new motor had a F on one and a M on the other. $69 for a brand spanking new Bosch motor is a lot better than that $200+ price for fan and all...

My guess is the fan relay circuit is functioning fine, otherwise it would not have melted the brushes....
Title: Re: 1987 K75s radiator fan frozen
Post by: mystic red on May 29, 2011, 12:36:31 PM
Where did you pick up the new motor?
Title: Re: 1987 K75s radiator fan frozen
Post by: cefalu on May 29, 2011, 12:53:49 PM
Euro Moto Electrics:

http://www.euromotoelectrics.com/BMW_Motor_Radiator_Fan_K_models_1983_1995_p/fan-k427m.htm (http://www.euromotoelectrics.com/BMW_Motor_Radiator_Fan_K_models_1983_1995_p/fan-k427m.htm)

I ordered it last Sunday and it arrived on Tuesday. Packed well, no drama. Seems like a good vendor.
Title: Re: 1987 K75s radiator fan frozen
Post by: mystic red on May 29, 2011, 12:57:41 PM
Euro Moto Electrics:

http://www.euromotoelectrics.com/BMW_Motor_Radiator_Fan_K_models_1983_1995_p/fan-k427m.htm (http://www.euromotoelectrics.com/BMW_Motor_Radiator_Fan_K_models_1983_1995_p/fan-k427m.htm)

I ordered it last Sunday and it arrived on Tuesday. Packed well, no drama. Seems like a good vendor.

Good to know, thanks!
Title: Re: 1987 K75s radiator fan frozen
Post by: Photog on May 29, 2011, 04:31:32 PM
Beemer Boneyard also sells the motors, at the same price, which is where I bought mine.
I'm in the process of doing the same swap. My brush holders are even worse than cefalu's

If you keep it clean, the coolant could be re-used since it's fresh. OTH, new stuff isn't all that expensive, worse case.
Title: Re: 1987 K75s radiator fan frozen
Post by: cefalu on May 31, 2011, 02:13:09 PM
I was careful with the coolant and used a clean container to drain it into for reuse. I also checked out the fan relay under the fuel tank and everything checked out fine. 2.9k ohms cold, fan switched on and overtemp bulb lit up. Good to go.