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Hello,

I've some issues when e..g going through high altitude passes with my 2005 k12s regarding the coolant temperature. Last time even the too hot coolant sign showed up, thankfully was on the top of the pass already.
An advice came that the radiator needs to be cleaned. The idea would be to have water-flow go through the radiator from behind towards to front side. Did anyone have a try with this kind of a method?
thanks in advance.
 

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Definitely do it from behind, and once a year if you live in a damp climate (like the UK). Mud & crud gets caked on the bottom quarter of the radiator
Don't use a high pressure hose - the vanes in the radiator bend very easily.

As you strip down, write down which faring bolts are long and which are short. It can feel a bit random, but best to stick with the original pattern. Take photos as you go, if it helps you remember the order of stripdown.

Note: This is for K1300S, but I believe the K1200S is the same layout, just a different fairing:
  • remove the lower fairing and belly pan (disconnect the thermometer on the left side fairing before removing - you'll see it)
  • remove the radiator-to-engine rod that runs below the radiator (the two safety circlips-like things pull off sideways with pliers, and then pull each end of the rod down and off - can be quite tight if the rubber grommit is fresh)
  • remove the mud channel and the radiator cover
  • unplug & unscrew the fan (the top right screw you will have to undo with pliers, you can't get a screwdriver in there - then file some flats on it so you can use a spanner on refitting - something like a 13mm one, I think)
  • remove fan downwards & out (which is why you had to remove the rod earlier)
  • brush the front with something delicate like a toothbrush. Brush up & down rather than side to side to minimse bending the vanes.
  • squirt water from behind - via 90 degree nozzle if you have one, since space is tight
  • consider soaking it first & having a couple of goes at cleaning it
 

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2009 K1300S, 2017 S1000R
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Boy this is right up my alley. I usually do this with the radiator out but that makes it a whole other deal that most can't handle due to the difficulty of refilling the coolant. So, I get a flashlight, a small O-ring pick and straighten as many front fin edges as I can. Then I pick out all the rocks and bugs that I can. Then air blow from the back using a soft air gun (OSHA) to blow out the dust. When I do this off the bike I get at least two teaspoons of dirt. Now I spray brake cleaner from the back to get non water based crap out. Air blow dry. Now I spray with strong soapy water and let it soak for 15 minutes, followed with a hose rinse. This job when off the bike takes me about two hours. Makes a huge difference. The shop will not do this in a normal service. They tend to say it is clogged you need a new one. If you ask when going in for a valve check maybe you could say you will pay for an extra hour to clean it.(?) Anyway all this makes a huge difference.
 

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What about checking and or changing your coolant? Have you done that? I mention it because the cooling system seems to have plenty of cooling capacity on my k12 and i never cleaned off the radiator. The only time temp started up was when it got low in the coolant reservoir and quickly recovered after topping it off. I changed the coolant about two months ago at 38,000 miles and motor is running even cooler now! I did clean the radiator since I had to pull it off the bike to change plugs and adj. valves. I dod not have much dirt. live in california.
 

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Boy this is right up my alley. I usually do this with the radiator out but that makes it a whole other deal that most can't handle due to the difficulty of refilling the coolant. So, I get a flashlight, a small O-ring pick and straighten as many front fin edges as I can. Then I pick out all the rocks and bugs that I can. Then air blow from the back using a soft air gun (OSHA) to blow out the dust. When I do this off the bike I get at least two teaspoons of dirt. Now I spray brake cleaner from the back to get non water based crap out. Air blow dry. Now I spray with strong soapy water and let it soak for 15 minutes, followed with a hose rinse. This job when off the bike takes me about two hours. Makes a huge difference. The shop will not do this in a normal service. They tend to say it is clogged you need a new one. If you ask when going in for a valve check maybe you could say you will pay for an extra hour to clean it.(?) Anyway all this makes a huge difference.
Bought my 08 K1200S around 6 weeks ago from someone who seemed genuine enough and without stripping it down outside his house. Rode it back around 55 miles with no issues. Took it in for a service (non BMW) and they did the usual fluids etc and the radiator. It now runs quite hot. When I initially rode it back the gauge remained in the centre and only went up 1 dash when I stopped to open the garage. Since then it runs 1-2 dashes over the centre, the fans come in but doesn't seem to bring the temperature down. Thought it might need vacuum bleeding at a BMW dealership so took it there (Not a wise move I know) as I don't think dealerships know what the word diagnosis means. The radiator is warm all over with no cold spots and without testing anything they stated it needed a new radiator. Has anyone had any issues with the thermostat as I've been given a second hand radiator from a lower mileage bike that had a slight leak to try. The one fitted is an aluminium radiator whereas the second hand one is plastic type. Also has anyone tried the ICE cool radiator additive which is supposed to reduce the temperature.
Thanks
 

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Discussion Starter #6
Definitely do it from behind, and once a year if you live in a damp climate (like the UK). Mud & crud gets caked on the bottom quarter of the radiator
Don't use a high pressure hose - the vanes in the radiator bend very easily.

As you strip down, write down which faring bolts are long and which are short. It can feel a bit random, but best to stick with the original pattern. Take photos as you go, if it helps you remember the order of stripdown.

Note: This is for K1300S, but I believe the K1200S is the same layout, just a different fairing:
  • remove the lower fairing and belly pan (disconnect the thermometer on the left side fairing before removing - you'll see it)
  • remove the radiator-to-engine rod that runs below the radiator (the two safety circlips-like things pull off sideways with pliers, and then pull each end of the rod down and off - can be quite tight if the rubber grommit is fresh)
  • remove the mud channel and the radiator cover
  • unplug & unscrew the fan (the top right screw you will have to undo with pliers, you can't get a screwdriver in there - then file some flats on it so you can use a spanner on refitting - something like a 13mm one, I think)
  • remove fan downwards & out (which is why you had to remove the rod earlier)
  • brush the front with something delicate like a toothbrush. Brush up & down rather than side to side to minimse bending the vanes.
  • squirt water from behind - via 90 degree nozzle if you have one, since space is tight
  • consider soaking it first & having a couple of goes at cleaning it
Thanks a lot, it's a great help, will try to find some pictures on the steps you mention. This weekend the coolant went into the red zone 2 times. Not good...
 

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Discussion Starter #7
What about checking and or changing your coolant? Have you done that? I mention it because the cooling system seems to have plenty of cooling capacity on my k12 and i never cleaned off the radiator. The only time temp started up was when it got low in the coolant reservoir and quickly recovered after topping it off. I changed the coolant about two months ago at 38,000 miles and motor is running even cooler now! I did clean the radiator since I had to pull it off the bike to change plugs and adj. valves. I dod not have much dirt. live in california.
Thanks for the answer; I'll check upon the coolant level. Doing so recently, it was fine, but who knows. The coolant system got cleaned a couple of months before, that part should be ok.
 

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3rd pic down shows the awkward top right screw, just near the cylinder head.

And from a little later in the same thread, the radiator support bar that you'll need to remove. It goes from the bottom of the radiator to the engine.
The rod pulls down and off BUT remove the circlips first!. It's sat in a rubber grommit, and feels quite well attached.

Lastly, apologies for cross-posting to another forum. Just trying the keep the beasts running!
 

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Discussion Starter #9
3rd pic down shows the awkward top right screw, just near the cylinder head.

And from a little later in the same thread, the radiator support bar that you'll need to remove. It goes from the bottom of the radiator to the engine.
The rod pulls down and off BUT remove the circlips first!. It's sat in a rubber grommit, and feels quite well attached.

Lastly, apologies for cross-posting to another forum. Just trying the keep the beasts running!
Thank you! It's a great description, the pictures help a lot. Yesterday I took off the fairings, removed the plastic shield, rinsed the pins with spraying a couple of times, then, with a hose, gently washed over the radiator from the back and from the front-side alike. Couldn't test it yet thoroughly, yet riding on a hot summer night back home, the temp of the coolant seemed under control already. :)
 
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