Overheating and fan diagnosis

[Lucas1983]

Hi everyone,

I have a similar issue.  On a separate threat I was trying to diagnose my radiator fan.  Long story short I felt (bike is old the temp gauge is not working) like the bike was overheating and the fan wasn’t turning on.  Turns out it takes a long time on idle for the fan to kick in.  One problem solved.. kind of.  Decided to clean the radiator, as some people suggested here on this forum just to find out the hose between the thermostat and the water pump was collapsed when the engine was cooling off.  I recently just acquired the bike after it was sitting for 3 years.  I replaced all the fluids except for coolant.  Fluid is green, which I assume needs to be flushed anyways.  Also, when I was topping off all the fluids the hose between radiator fill and reservoir cracked, so I replaced that. Now I think I either have some air in the system or the cap is bad and not functioning correctly.  I believe the two issues are connected the collapsed hose and the original fan/ overheating concern.  What do you guys think? Sorry for the long post.

[alexg]

I believe it is the check valve of the radiator cap that it is stuck.

[Lucas1983]

Thanks Alex.  I am assuming the same thing. Will be diving into it today.  Also, I have been reading a vacuum tool is not really necessary on those early k bike, 1100 and older is that true?  Can someone confirm please.

[Laitch]

On a separate threat I was trying to diagnose my radiator fan.  Long story short I felt (bike is old the temp gauge is not working) like the bike was overheating and the fan wasn’t turning on.

There's a temperature light in the instrument cluster that lights when the engine overheats. Why do you believe the Brick was overheating; was steam coming from the cap or the coolant reservoir?

Green coolant is just green coolant. Its color could have been factory supplied. Replace the coolant regardless.

You don't need a vacuum tool for coolant tasks; you need one to remove mouse nests, leaves and spider webs from the air filter in the air intake box. 

[Lucas1983]

Laitch, thanks for moving the post. Besides the annoying abs light, the temp light never came up and no steam. I am coming from a F850gs world where the engine is tosty but on the brick I feel like my lags are roasting in the oven lol. I agree green is green, but all my other bmw bikes had the blue coolant. 
I can deal with the heat now that I know the fan kicks in I am more concern with the collapsed hose.  Today I will drain the coolant,  clean the cap and ensure passage between radiator and reservoir is clear.  Will report back. Thanks again.

[Laitch]

Of course, the hose that collapsed is a good candidate for replacement. Some hoses collapse from blockages in passages or lack of venting. Here's an informative article. BMW's coolant concentrate is blue but others with composition that is suitable for our Bricks have different colors.
Flush the system thoroughly and follow BMW's procedure for coolant replacement and removing air from the system in the order presented. For the benefit of those who haven't yet downloaded the K100/K75 2V manual from this site. There are also innumerable posts from qualified shade tree mechanics describing the procedure. It's a straight forward task, once the fuel tank is accessed.
 

[frankenduck]

The hose should not collapse. As the bike cools it should suck coolant from the reservoir via the radiator cap.

If you buy a new rad cap from BMW you do not need to buy the rad cap gaskets shown in the parts diagram. New ones come with the cap.

[Lucas1983]

Happy to report the brick is flying again!! Radiator cap was stucked.  Bit of vinegar as few of your recommended and it works again. Thank you for all the responses.

[Laitch]