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"KRS/GT" Technical Q&A K1200RS/GT Technical Questions/Answers

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Old 01-18-2019, 01:11 PM
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Post Coolant overflow after hot shutdown...

Removing Trapped Air from the Cooling System

Would this technique for automobiles work on the K12RS???

Quote:
Any time a cooling system is opened up for service, air gets in. Depending on how much air enters, it can cause problems for your cooling system....

If air is introduced to the cooling system, it can get trapped and form a bubble in the liquid. This prevents the continual flow of liquid, and can create hot spots in the cooling system, depending on where the air is trapped.Symptoms are an engine that runs hotter than normal, a temperature gauge that indicates hotter temperatures during high speed (highway) operation, inconsistent heat coming from your heater, and overflowing when the engine reaches normal operating temperature or after a hot shut down. The reason for all these symptoms is simple: the air can't remove or dissipate heat the way liquid can, and it prevents the coolant from flowing properly through the system. Coolant also expands as it heats up, which is the reason it overflows. The trapped air takes up space in the cooling system normally occupied by coolant, so there's no place else for it to go.

...

In essence, you want to "burp" your cooling system to remove the trapped air. Start with a cold engine. Remove the radiator cap and fill it to the recommended level with a 50/50 mixture of antifreeze and water. Make sure any auxiliary tanks are also at the proper cold fill level. With the radiator cap off, start the engine. Make sure your heater is set to maximum defrost. This is important because most cars, especially those with automatic temperature control heating and air conditioning, allow coolant to flow through the heater core while warming up, to help clear the windshield. If controls are set for heat, the system may keep the heater core closed off until the engine warms up. You don't want that to happen in this case. You want 100% circulation of the coolant. Let the engine operate long enough to warm up enough to reduce the idle speed to a normal idle.

Let it idle until it's at normal operating temperature, keeping an eye on the temperature gauge or light. Do not let your car overheat! .... Once the thermostat begins to open, it's also very important to not rev the engine, even slightly, as this will force coolant out of the open radiator.

You might notice some bubbling of coolant out of the open radiator during warm up. This bubbling is normal if you have air trapped in your system, and is caused by the air escaping as it reaches the area of the open radiator cap. Unless the bubbling is excessive, continue to let the engine run at idle for a few minutes once it reaches normal operating temperature, then shut it down. Allow the engine and cooling system to cool off, preferably overnight. Then check your coolant level again. If it dropped, that means you've displaced some of the air in your system. Refill to proper levels, and repeat the process. Do this until the level doesn't drop any longer, then replace your radiator cap and check your coolant levels at least monthly, or weekly during hot weather.

from an automotive site: http://automotivemileposts.com/garage/v2n15.html
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Old 01-18-2019, 02:42 PM
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Re: Coolant overflow after hot shutdown...

No need for most of that on the K.Fill, run for a minute and recheck.The Ks are probably the easiest bikes around for coolant replacement.

My car is a much different story.Fill cap is on the engine,not the rad.Fill and run without cap for +15 minutes all the while watching the air escaping/coolant going down and keep adding coolant until level is stable and no more bubbles.
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Old 01-18-2019, 03:34 PM
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Re: Coolant overflow after hot shutdown...

The "slant" motor K bikes require the use of a vacuum pump to remove air bubbles from the cooling system. As Pierre noted, the "brick" motor bikes don't.

Here's the page from the BMW manual, (grainy copy, best I could do) the Clymer manual has the same, or similar instructions. The scanning process is not the clearest, but basically you drain the cool engine by disconnecting the lower radiator hose, and drain the overflow tank too, to the extent that disconnecting the hose doesn't drain it as well. Reconnect everything, fill the radiator with the appropriate coolant. Turn the engine over without starting it (I pull the lead from the coil) top up the radiator, squeeze the lower radiator hose to "burb" any air bubbles, top off, and go. Keep an eye on the fluid level in the overflow tank after a ride where the engine gets to operating temperature.

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Old 01-19-2019, 02:42 AM
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Re: Coolant overflow after hot shutdown...

Quote:
Originally Posted by CJS350
The "slant" motor K bikes require the use of a vacuum pump to remove air bubbles from the cooling system. As Pierre noted, the "brick" motor bikes don't.

Here's the page from the BMW manual, (grainy copy, best I could do) the Clymer manual has the same, or similar instructions. The scanning process is not the clearest, but basically you drain the cool engine by disconnecting the lower radiator hose, and drain the overflow tank too, to the extent that disconnecting the hose doesn't drain it as well. Reconnect everything, fill the radiator with the appropriate coolant. Turn the engine over without starting it (I pull the lead from the coil) top up the radiator, squeeze the lower radiator hose to "burb" any air bubbles, top off, and go. Keep an eye on the fluid level in the overflow tank after a ride where the engine gets to operating temperature.


Just a nit-picking comment.
If the sole purpose is to drain radiator in order to refresh the coolant, there is no need to remove the lower radiator hose, as there is a drainplug on the radiator. You will find it on the gearshifter side of the bike, next to the lower screw for the radiator cooling fan.
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Old 01-19-2019, 11:45 AM
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Re: Coolant overflow after hot shutdown...

A drain plug on the radiator?Not on a K-brick.

Might be one on the slant Ks as the rad is way down.On the bricks rads are above the motor.Drain cooling system at the water pump hose.

What the KRS/GT have on the L/H rad is a coolant bypass hose.Small hose at the top rear center of the L/H rad.Connects the rad directly to the top of the engine and that bypasses the main coolant hose.Prevents them air pockets as you refill or on the road.

OP had another thread about overflow a while back?What made mine overflow a few years ago sure wasn't an air pocket.....!
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