Author Topic: Coolant change…  (Read 4247 times)

Offline Atabeach

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Coolant change…
« on: May 01, 2024, 05:39:23 PM »
 94 K75 8500 miles. Gentlemen, I decided to flush radiator and cooling system. The fan is now turning on more frequently in cool weather… ( not overheating, no light  )
  Ok drained everything, started from scratch. I can only get 2.25 liters into machine….there HAS to be air in block!
   1) You could not possibly add coolant more slowly. 2) kneaded upper and lower hoses on right side, first while sitting…then while pulsing starter…both times with radiator cap on ( that may matter ) 3) The expansion tank is filled, cap tight…also I checked thermostat & gasket…
Question #1 where is the air “ sitting” is there a hose clamp where I can burp air.?
#2 will the  air work its way out eventually?
#3 I live in Florida….right now it’s 70. Can I run K75 without thermostat? TIA
  • Ponte Vedra Fl
  • 1994 k75, 2001 Harley Dyna, 1990 K75ssss, & my favorite 2006 Vespa LX150!

Offline Laitch

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Re: Coolant change…
« Reply #1 on: May 01, 2024, 11:13:10 PM »
Ok drained everything, started from scratch. I can only get 2.25 liters into machine….there HAS to be air in block!
   1) You could not possibly add coolant more slowly. 2) kneaded upper and lower hoses on right side, first while sitting…then while pulsing starter…both times with radiator cap on ( that may matter ) 3) The expansion tank is filled, cap tight…
Can I run K75 without thermostat? TIA
Burping with the cap on the radiator after filling the radiator cannot be done any more successfully than burping with your mouth closed after chugging a Corona.  :laughing4-giggles:


Starting over:
  • Empty the coolant reservoir.
  • Remove the radiator cap.
  • Fill the radiator with coolant to the neck of the filler opening.
  • Pulse the starter.
  • Knead and repeat until there are no bubbles releasing.
  • Add coolant until it reaches the neck of the radiator filler opening.
  • Replace the cap.
  • Fill the coolant reservoir to MAX.
If 2.5 liters is all it takes, that's all it takes but it's likely to take more if you do the procedure correctly. Just don't worry about it. Instead by a Spal 6.5" puller fan and use it to replace the stock BMW fan; it's sturdier and more powerful. If you've already done that, don't worry about that either.  :laughing4-giggles:

Leave the thermostat in. It helps the engine warm up sooner and by doing that, conserves fuel and limits carbon deposits on combustion chamber components. I've got personal experience that it can freeze in Immokalee, so wear your mittens if you go there in January, just to be on the safe side.  :laughing1:
  • Along the Ridley in Vermont.
  • 1995 K75 89,000 miles

Offline frankenduck

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Re: Coolant change…
« Reply #2 on: May 01, 2024, 11:34:26 PM »
My experience:

Kneading 30 year old rad hoses repeatedly is not a good idea.

You could end up like I did 1,000 miles from home in a parking lot under a tree:
http://dws.x10host.com/tours/120415_rm2sea/120415_pics/DSC03266.JPG

And it was a Monday so even though I was in The Bay Area with several dealers nearby they were all closed.

When touring I now always carry Rescue Tape.


Once I had a Collie pup. Dug a hole and covered him up. Now I sit there by the hour. Waiting for a Collie-flower.
New to K bikes? Click here.
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Offline Laitch

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Re: Coolant change…
« Reply #3 on: May 01, 2024, 11:37:54 PM »
My experience:
Kneading 30 year old rad hoses repeatedly is not a good idea.
You could end up like I did 1,000 miles from home:
Some people get carried away when kneading. You're lucky you didn't get a rash, too.
  • Along the Ridley in Vermont.
  • 1995 K75 89,000 miles

Offline frankenduck

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Re: Coolant change…
« Reply #4 on: May 01, 2024, 11:57:41 PM »
It was not a fun day. I walked to a nearby auto parts store and bought some rad hose repair tape that ended up being complete garbage. Even though I applied several layers and zip-tied it the hose still leaked.

http://dws.x10host.com/tours/120415_rm2sea/120415_pics/DSC03267.JPG

I rode from Santa Cruz to a friend's house in Sacramento. Since it was still leaking I had to lane split stop-n-go rush hour traffic at 40ish to keep the temp gauge needle from pegging. Lane splitting at 40 in stopped traffic is not something that I would normally do.
Once I had a Collie pup. Dug a hole and covered him up. Now I sit there by the hour. Waiting for a Collie-flower.
New to K bikes? Click here.
K Bike Maintenance & Mods: Click here.
Buy parts here.

Offline Laitch

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Re: Coolant change…
« Reply #5 on: May 02, 2024, 11:05:11 AM »
 177381
  • Along the Ridley in Vermont.
  • 1995 K75 89,000 miles

Offline bluekbike

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Re: Coolant change…
« Reply #6 on: May 04, 2024, 02:01:19 AM »
I recently bought a Spal 6.5" puller fan from Jeep Specialties, cost $60 plus $15 to ship. Price has gone up ten bucks but it's still a great deal compared to some alternatives. It's going in my 94 1100RS soon.
https://jeepandtruckparts.com/products/spal-325-cfm-6-5in-fan-push-va22-ap11-c-50s?variant=43733792227571&gad_source=1&gclid=Cj0KCQjwltKxBhDMARIsAG8KnqVaGvFJpGVO4_MocuxjJkE6eYtIPNAhkQdlv0J3Wh9uBG3J0HsoATsaAvdLEALw_wcB
  • Bainbridge Island, Washington USA
  • 94 K1100RS

Offline frankenduck

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Re: Coolant change…
« Reply #7 on: May 04, 2024, 04:17:27 AM »
I recently bought a Spal 6.5" puller fan from Jeep Specialties, cost $60 plus $15 to ship. Price has gone up ten bucks but it's still a great deal compared to some alternatives. It's going in my 94 1100RS soon.
https://jeepandtruckparts.com/products/spal-325-cfm-6-5in-fan-push-va22-ap11-c-50s?variant=43733792227571&gad_source=1&gclid=Cj0KCQjwltKxBhDMARIsAG8KnqVaGvFJpGVO4_MocuxjJkE6eYtIPNAhkQdlv0J3Wh9uBG3J0HsoATsaAvdLEALw_wcB

$72 shipped on Amazon:
https://www.amazon.com/dp/B003PB44TO/
Once I had a Collie pup. Dug a hole and covered him up. Now I sit there by the hour. Waiting for a Collie-flower.
New to K bikes? Click here.
K Bike Maintenance & Mods: Click here.
Buy parts here.

Offline Atabeach

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Re: Coolant change…
« Reply #8 on: May 04, 2024, 01:55:05 PM »
OK Laitch…I did get a little more fluid in her this time around Thanks!  factory says 2.5L… I think the belly pan I installed is making the fan run a little more often…PS…looking at a Blue 1990 K75S 41k to add to the corral. I’ll check for leaks near the clutch boot, also the bolt adjustment… Anything else? If I purchase…I’ll need to go through her pretty good including spline lube. Let me know of any obvious things to check specific to K bikes…..TIA
  • Ponte Vedra Fl
  • 1994 k75, 2001 Harley Dyna, 1990 K75ssss, & my favorite 2006 Vespa LX150!

Offline Laitch

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Re: Coolant change…
« Reply #9 on: May 04, 2024, 06:52:12 PM »
I’ll check for leaks near the clutch boot, also the bolt adjustment… Anything else? If I purchase…I’ll need to go through her pretty good including spline lube. Let me know of any obvious things to check specific to K bikes…..TIA
TIA is not accepted; only TATM is. :laughing4-giggles:

When idling or riding in slow moving South Florida traffic, the fan is going to run; that isn't a bad thing. It means the system is working. It shouldn't be running at speed. Let the bike idle for 15 minutes. If the fan doesn't start, that's a problem. The fan might run slightly less often if you were running 50:50 coolant:distilled water in hot weather. If the radiator fins are clean, if the coolant isn't cloudy, if the starting speed lever has two stages, there's hope. If love bugs are still problematic down there, you'll need to back-spray the radiator more often. You'll need to do that if you often ride at night, too.


Verify that the bulb check triangle in the instrument cluster is lit when the key is turned to On and goes dark after the front and rear brakes are activated

Look at the coolant reservoir. If it's below the MIN line, the previous owner's head isnt screwed on correctly and there might be other examples of neglect, like low or no oil in the rear drive and ancient fluid in the brake reservoirs. The brake fluid should be clear.

Leaks at the clutch boot aren't necessarily serious. They can be caused by lack of tension placed on the clutch nut by the clutch arm bolt because the basic clutch adjustment was incorrectly set, or by a loose boot clamp. Oil from the transmission/engine weep hole, or water/oil from the combination pump weep hole will take some disassembly to repair if the leaks are dripping significantly daily.
  • Along the Ridley in Vermont.
  • 1995 K75 89,000 miles

Offline Atabeach

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Re: Coolant change…
« Reply #10 on: May 04, 2024, 08:10:10 PM »
Thanks Laitch, wish me luck…Imma turn this puppy into my daily driver as my current “ c “ has less than 9 k on the clock…I want to keep her virginity palpable…
  • Ponte Vedra Fl
  • 1994 k75, 2001 Harley Dyna, 1990 K75ssss, & my favorite 2006 Vespa LX150!

Offline Atabeach

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Re: Coolant change…
« Reply #11 on: June 26, 2024, 07:38:25 AM »
AAAARGHH! Two K75 machines, one eats 2.25 of coolant…the older 42k rat eats about .650 MORE. My rehab is sitting in the same Florida sun, the fan rarely kicks on. Same distance, same weather…the 9k bike fan cycles on repeatedly. I used a thermal gun on radiator….there seems to be no blockage….further this fan RARELY kicked on before I changed fluid. The fan rarely kicked on BEFORE coolant change…. Not that there is a problem…but why is one bike taking more fluid and running hotter?
  • Ponte Vedra Fl
  • 1994 k75, 2001 Harley Dyna, 1990 K75ssss, & my favorite 2006 Vespa LX150!

Offline Laitch

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Re: Coolant change…
« Reply #12 on: June 26, 2024, 07:18:17 PM »
I wouldn't worry about the difference in coolant volume, but you seem to be a teeny bit conditionally obsessive about things in general, Atabeach.  :laughing4-giggles: 
Anyway, turning our attention to the 9K Brick, you need to get the air that's in the coolant system burped out of it so you can fill it more, and if you haven't changed the radiator cap gaskets, do that. Verify that the cap isn't cracked, too



  • Along the Ridley in Vermont.
  • 1995 K75 89,000 miles

Offline Atabeach

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Re: Coolant change…
« Reply #13 on: June 26, 2024, 10:17:45 PM »
Obsessive may be an understatement, thanks for the compliment..The twins run fine and don’t overheat. I poured slowly and massaged the 9k hoses vigorously. The rat got no such treatment yet took more fluid. Less than 15 minutes of driving kicks the 9k fan on. Again…this didn’t happen prior to the coolant change, I did not change the thermostat but have since checked the gasket…I can run the rat all day without the fan kicking on. I will be laying up the 9k shortly to obsess over the grub screw and add….a temperature and fuel gauge. I guess I’ll change all 4 gaskets.
  • Ponte Vedra Fl
  • 1994 k75, 2001 Harley Dyna, 1990 K75ssss, & my favorite 2006 Vespa LX150!

Offline Laitch

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Re: Coolant change…
« Reply #14 on: June 26, 2024, 11:56:07 PM »
Obsession can often be a burden, instead of a help.
If the fan kicks on often, there could be a few causes: a thermostat that isn't opening fully is one of them. If you gently remove the thermostat being careful to keep its gasket intact, you can do a test of it to see if it opens fully and at the correct temperature. Put a thermometer in a pan of water, put the thermostat in there with it then bring the water to a boil. I'd tell you the temperature at which the thermostat should open, but I think you should find it yourself in the manual; however, somebody here is likely to tell you.  :laughing4-giggles:
  • Along the Ridley in Vermont.
  • 1995 K75 89,000 miles

Tags: 2.5 liter