BMW K75 Motorcycle Radiator & Fan Change

The electric fan failed on my 1987 BMW K75 and caused the radiator to split. In this video I change the radiator and then later insert a new aftermarket fan. I used a 7" AeroLine Electric Radiator / Intercooler 12v Cooling Fan For Classic Car bought from ebay. Update 2023. Since making this video i have replaced the heated grip switch with a conventional handlebar switch.

[@frankdedeyne4200]

I had the same problem. Thanks to your videos is was an easy job!!!!

[@johnnysevengun]

Glad it helped

[@harrothepilot]

I think the fan may be a bit of a weak point. My ‘93 S is on its second one after the first suffered EXACTLY the same failure as yours, the brush’/brush holder assembly melted but on mine, jammed against the commutator. I replaced it with a genuine unit, but if it happens again ( quite likely, Aus and hotter weather ) I am going to go the same way as you, aftermarket. The bike has 32k kms on it now, about 20k miles I think. Great explanatory vid, cheers.

[@HakanKoseoglu]

My K1100LT's fan is kaput and replacing it turned to a nightmare. Stuck screws, bits not coming out, complete lack of understanding how some parts work and the vagueness of the repair manual really put me off this bike.

[@johnnysevengun]

I had a K1100LT for a couple of years. It was too heavy and too complicated and went wrong a lot because dirt got into everything. I much prefer the unfaired bikes.

[@avomanavoman]

+.

[@amac9917]

ive just bought one of the fans you used after my fan also stopped working. ive just noticed its rated at 80w which is more than double the original. did you notice any issues with your bike after fitting it when it switched the fan on automatically? ie not when you manually switched it on... i'm thinking whether the cabling needs uprated to cope....

[@johnnysevengun]

I haven't had any problems with it but I did not reconnect it to the temp switch. I connected it to the auxiliary under the tank which I was using for heated grips. This must be higher rated. In my case the temp switch was switching it on too late which is what boiled my first radiator. I am in the UK and it seldom gets hot enough to heat the bike right to the point it automatically switches on. I think it has only done it twice in the 18 years I have had the bike. This must be why the fan fell apart (from lack of use). I have also left the thermostat out - this means the bike takes ages to warm up in the winter but I wouldn't go out on the bike below zero degrees anyway.

[@amac9917]

excellent thanks. i'm fitting it now. i did measure the fan current with a 12v battery , and it was only 3.2 amps ie about 40 watts - so maybe the existing wiring will be fine. i'll check again later. I plan to put an override switch on - but connect it to ground the appropriate input pin of the fan relay so the ecu unit can still turn in the fan on or/ i can. good video. the reason you got pulsing on and off when you used the heated grip switch is that the switch unit pulses the power to the grips to give approx half the heating effect on low power.... (BTW). i'm in scotland and i fully expect the normal high temp required to trigger the fan will never actually be required!

[@johnnysevengun]

@@amac9917 Sounds good. The fan only came on twice in the 19 years I've had it. By which time the radiator was shot.

[@billpumarejo699]

How do you connect the by pass switch to the fan?

[@johnnysevengun]

You can either use the heated grips connection under the tank or run a new cable directly to the battery and earth and then through a new handlebar switch. I show the switch I ended up with in another video. kzbin.info/www/bejne/nai1i3yBrKh1hrM

[@Borrelaas]

3:30 if your fan was broken, its no surprise that its only turned on two times

[@johnnysevengun]

It just does not get hot enough in this country for it to turn on - so after nearly 30 years it gave up.

[@Borrelaas]

@@johnnysevengun but how can you know it doesnt get hot enough if the fan is broken? it couldve been broken for a long time and you thought the engine was not running hot since it didnt turn on

[@johnnysevengun]

@Markus Rubach That is a good question. I have a temperature gauge on the engine that reads 80C as a normal running temperature. The water should be at 88C in the radiator at this point. In England the ambient temperature seldom gets above 25C and is usually much cooler. The fan should cut in at 103C and the warning light comes on at 111C - too late to save the radiator. So it can go for 25 years without ever cutting in. Then we have the hottest day in the UK for decades at 35C and I cane the bike down the motorway and the fan finally kicks in - which probably broke it - but I would not know until we had the next hottest day for decades.

[@Borrelaas]

@@johnnysevengun ah, i didnt consider the temp indicator. Dont have it on mine anymore. Well fair enough ^^,

[@scottlawhon3999]

How do I take fan off I took my bolts out but can't get fan out I have zx750p

[@johnnysevengun]

Sorry - can't help you there as I don't have that bike. Try the forums.

[@Feinrizulwur]

You are using wrong coolant. Flush well and fill with de mineralized water and use the red coolant VW. The problem is not Tha radiator. You can destroy the motor, valves and seats. Good luck

[@johnnysevengun]

I am not using the wrong coolant. Orange coolant was not invented until 1995 and my bike is a 1987 model. I always use blue and have done for 20 years and 65.000 miles. The bike has done about 90.000 miles and the engine has never been opened - must be doing something right. ;).

[@Feinrizulwur]

@@johnnysevengun It was an easy solution. There are other products with inhibitors for aluminium and they have been available for many years. The problem is poor knowledge at BMW dealers.

[@frankdedeyne4200]

I use the blue coolant...

[@goldgeologist5320]

The Kbike fans are from a rear defrost window of a car! They are not good for external exposure. Junk! Replace with a Spal fan.

[@johnnysevengun]

What on earth are you on about? The fan on my K75 lasted over 25 years. You can now buy a replacement motor to fix it. What kind of car has a fan to defrost the rear window? A Lada? Spal are good but the classic car fan I used is excellent.

[@ottonormalverbrauch3794]

Mine from '89 has just recently seized so I guess the fuss is a bit unwarranted for?