Overheating

2009 K1300S -42,000 km. My bike usually runs with 3 bars on cooling gauge and might run up to 4 bars on start-up or heavy traffic. Recently it will run up to 6 or 7 bars ( no warning light comes on)and then it may return to 3 bars or may stay and fluctuate between 6 or 7. Am I correct in assuming a thermostat malfunction or perhaps an other problem???????? I removed the rad plastic and freed up the fan and forced air from the backside (attached photo shows the large amount of crud collected.) This had no effect on the cooling fluctuation. (can't hurt) I am assuming there is a problem and thermostat replacement should correct, comments appreciated.

ARTEMERY said:

2009 K1300S -42,000 km. My bike usually runs with 3 bars on cooling gauge and might run up to 4 bars on start-up or heavy traffic. Recently it will run up to 6 or 7 bars ( no warning light comes on)and then it may return to 3 bars or may stay and fluctuate between 6 or 7. Am I correct in assuming a thermostat malfunction or perhaps an other problem???????? I removed the rad plastic and freed up the fan and forced air from the backside (attached photo shows the large amount of crud collected.) This had no effect on the cooling fluctuation. (can't hurt) I am assuming there is a problem and thermostat replacement should correct, comments appreciated.

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I doubt it's the thermostat -- they rarely fail, and your symptoms don't match a failed-shut thermostat.

Sounds more like a fan not running. That could be due to any component between the coolant temp sensor and the fan -- the temp sensor, its wiring to the computer, the wiring from the computer to the fan (through a relay? - I don't know for this model K), or the fan motor itself. Step-by-step checking of the components (sensor resistance, fan operation with jumpered 12V applied, etc.) will be required to methodically isolate the problem.

If it were a failed open thermostat,

The fan motor is operating ( I can hear it) Could it be possible that the thermostat is only partially opening sometimes and fully opening othertimes???????

Could also be a bubble in the system..Any fluid changes precede this behavior or evidence of a leak?

That was going to be my question.....was a radiator fluid change done? Especially, was one done without using the vacume to ensure all entrained air is released? Or is it unusually hot weather where you are, combined with slow/stop and go riding? ie: does the guage go back to normal once you get some cooling air going? I don't recall how many bars there are, but 6 or 7 seems like it would be about 3/4 the way up? I have to admit, even with 105 temps yesterday and also at the track a few weeks ago, I have never noticed mine, so I don't know where it would/should be in those conditions. Theoretically if the idiot light doesn't come on you should be fine, but fluctuating that is not tied to your movement through the air is wierd and would make me want to get the rad fluid changed by someone you know is doing it properly (you or a dealer or trusted and watched friend....?).

you photo has convinced me to go out and clean mine!

Coolant level was low. My K1300S manual indicates checking level on outside of overflow tank. This tank is made out of opaque plastic and this old guy simply cant see a level line. On the inside of the overflow tank is a pin, which in other model manuals (K1300R) it is refered to as the LEVEL INDICATOR PIN. There is no mention of the LEVEL INDICATOR PIN in the K1300S manual but using the pin would make level checks a lot easier. Any guidance would be appreciated.

on our K12S's, there is a MAX/MIN mark on the resevoir tank where the black outer half meets the opaque white inner half towards the rear of tank . Really hard to see w/out strong light...to my older eyes anyway.
Depends on what color coolant as to how easy it is to see as well

If you ovefill, it will just expand out and down the overflow tube, so not that big of a deal.
If it is real low, I would wonder where the original coolant went? Maybe the overheating and the crud you cleaned out is the answer to that

My next step will be to have the BMW dealer do a flush and pressure test. Perhaps this will give some clue to the missing coolant. When I find out the cause I will pass the info. on. Untill then I will continue to monitor using the LEVEL INDICATOR PIN.

ARTEMERY said:

On the inside of the overflow tank is a pin, which in other model manuals (K1300R) it is refered to as the LEVEL INDICATOR PIN. There is no mention of the LEVEL INDICATOR PIN in the K1300S manual but using the pin would make level checks a lot easier. Any guidance would be appreciated.

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Our 2011 K1300Ss have the pin inside the tank, and that's what I use to monitor the coolant level.
At least the cap is easy to get to on the 1300.

A guy on one of the F800 boards solved the "hard-to-see" problem on his overflow tank by putting a small LED light behind the tank. It makes the opaque part translucent and the fluid level is easy to see, day or night. Wired to a keyed circuit. The $1 solution.

"I removed the rad plastic and freed up the fan..."

Here's my guess, based on this part of your post:
The fan got crudded up and was stuck. During a ride, the temps got too hot (and you didn't notice the temp gauge) causing some coolant expansion into the tank. The amount was probably higher than normal due to the slight overheat. It may have been a large amount, large enough to overflow the expansion tank (check for signs of coolant overflowing the tank). When it cooled, the engine sucked the coolant back in like normal, but there wasn't enough and it might have sucked in a bubble.

That's a totally wild ass guess based solely on what I know about cooling systems, which isn't as much as lots of guys on this forum and k-bikes.com. And that part of your post makes me think there have been times when your fan isn't running.

Last weekend I rode through Mojave (104 degrees) and the San Fernando Valley (112 degrees) with the gauge steady at 3 bars, or less than half. Even when stopped, it only went to half (4 bars).

By the way, I wear a cooling vest, and it works.
Also, I put a Fenda-Extenda on mine, and the radiator area has stayed pretty clean.

A cooling flush is a great idea because the dealer will fill it correctly.

Clean your radiator!

I had overheating problems in slow traffic/hot weather, and discovered my radiator was significantly clogged with road gunk. Removed radiator, took to radiator shop, reinstallled, no problem.

djdgh said:

I had overheating problems in slow traffic/hot weather, and discovered my radiator was significantly clogged with road gunk. Removed radiator, took to radiator shop, reinstallled, no problem.

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Word. Recently I had my radiator partially removed for a valve clearance check and it was amazing how much junk was in between the radiator fins. I just blew it out with compressed air from the back side, seemed to get 95% of it out.
Clearing the radiator fins should be on the routine maintenance list for sure.

I had a similar problem on my R1150R. Wait, no I didnt, its aircooled.

cele0001 said:

I had a similar problem on my R1150R. Wait, no I didnt, its aircooled.

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Being from Florida you have to be familiar with these and have never ridden your R1150R thru several miles of them

Those side scoops work very well at collection and kinda block the coolers


not my bike...you get the idea

That is not fun timof the year here. I will still take love bugs over snow and ice and salt and....
But now thinking about it you are right I have to to figure something out when the time comes.

It was mentioned that the BMW thermostats seldom fail, but your description is that of a sticky thermostat. In most vehicles thermostat failures are common, lets face it the technology is BASIC and over 100 years old. Before I spent $$ on the dealer, I would replace the thermostat. It can't hurt to flush the system if it is due, but not convinced that is the problem, from your description.

My fix

I have two K1200S bikes (his & hers). Two years ago they began overheating at nearly the same time. Long story short:

The radiator fins are plugged with crap. Pull off both side panels and the belly pan. Yank off the radiator screen then take a brush and remove the big chunks. Gently rub the fins with a wire brush. You'll be stunned how much road tar, dirt & bugs come out. For good measure, apply Simple Green liberally to the fins, wait a half-hour, then shove a hose behind the radiator and flush the last bits onto the driveway.

I just did these steps again a few weeks ago as one of the bikes started overheating again. It's a bit of a bother but easier than pulling the radiator off.

My overheating problem was traced to a leaking water pump seal and was repaired buy BMW under waranty a few months after the warranty had expired.