Coolant overflow?

[juliusmichaelhonrada]

I had a coolant overflow , i have the bike parked for 1 week , before that the coolant is halfway before full(when you look in the rad. cap) and the overflow tank in the minimum sign.

After that week which is today i checked the coolant and its full in the radiator(as in coolant touches the cap bottom) and the overflow tank empty so i filled the overflow tank in the minimum sign, then off i go , me and my brother went to a gasoline station to put proper psi in the front tires because it was hard to steer while the bike is idling at 5000rpm , coolant is boiling and just splurged out of the overflow hose in the overflow tank going straight to the muffler and smoke everywhere , the people in the gasoline station panicked thinking it was gasoline

[FrugalNinja250]

If the coolant was actually boiling then either your thermostat is stuck closed or the radiator cap is defective.

Kawasaki runs pressurized cooling systems. Since there's no pump to increase the pressure, Kawasaki relies on thermal expansion to create pressure. As the engine warms up the coolant heats, and thus expands. To create pressure, the radiator cap has a pressure valve in it set to stay closed until around 15psi. So, the coolant pressure rises to 15psi and any excess pressure is bled off through the valve and that coolant goes to the overflow reservoir.

It's important that the pressure is maintained because that increased pressure significantly increases the boiling temperature of the coolant. The thermostat IIRC opens at 195°F and the fan comes on at 230°F. If the radiator cap pressure valve fails to keep pressure in the system then the coolant may boil, and that boiling will create steam which will push coolant out of the motor, through the overflow bottle, and out on the ground.

If the thermostat is stuck or failing then it will allow the coolant to overheat also. A common failure mode for wax pellet-style thermostats is for the wax to leak out, causing the disc to be closed by the spring. Often times if you rev the motor the water pump can push coolant against the disc hard enough to force it open and circulate coolant, but as soon as the RPMs drop the disc closes again and the temperate starts riding as coolant flow is being restricted.

Note, it is critical that the coolant be a proper mix of antifreeze and water. The antifreeze needs to be ethylene glycol, of the type specified for the bike.

[Motofool]

You may have had some pockets of air trapped in the system:

http://faq.ninja250.org/wiki/How_do_...ling_system%3F

The loop is under pressure while the coolant is cooling the engine and heating the radiator.
The volumen contained inside the loop is constant, because of that, less amount of hot coolant can fit in there and the excess of it goes into the reservoir.

While moving from a high pressure place (closed loop) to atmospheric pressure (reservoir), steam flash happens, which means that some of the liquid suddenly becomes steam (which occupies 600 times more volume); hence the crazy bubbling inside the reservoir.

Please, see this:
https://en.m.wikipedia.org/wiki/Steam_explosion

[juliusmichaelhonrada]

i dont know if this is possible but i my thermostat is stucked open when i flushed the system with water , from the water pump tube i am putting pressurized water then it comes out to the radiator side while the hose from the pump to radiator is disconnected.

about the overflow tank , is the cap necessary? because im using a coca cola cap and i think it does not pressurize

[Motofool]

Originally Posted by juliusmichaelhonrada

i dont know if this is possible but i my thermostat is stucked open when i flushed the system with water , from the water pump tube i am putting pressurized water then it comes out to the radiator side while the hose from the pump to radiator is disconnected.

about the overflow tank , is the cap necessary? because im using a coca cola cap and i think it does not pressurize

Your bike has no T-stat, which is OK for where you live.
Somebody has removed it.

Overflow tank must breath, it should not pressurize.
The cap does not close, it allows air in and out freely.

[Alex]

Originally Posted by juliusmichaelhonrada

while the bike is idling at 5000rpm , coolant is boiling and just splurged out of the overflow hose in the overflow tank

Why/when is the bike idling at 5000 rpm? That alone would cause overheating if the bike wasn't moving through the air at that point.

[juliusmichaelhonrada]

Originally Posted by Alex

Why/when is the bike idling at 5000 rpm? That alone would cause overheating if the bike wasn't moving through the air at that point.

the bike cylinder #2 has low compression it would only idle at 4000+ otherwise it would stall

[Alex]

Then nothing is necessarily wrong with your cooling system. There's something very wrong elsewhere.

[juliusmichaelhonrada]

Originally Posted by Alex

Then nothing is necessarily wrong with your cooling system. There's something very wrong elsewhere.

checked the bike today, cant see the coolant down in the radiator cap and no coolant in the tank , also found out the wiring i made for the fan on/off switch got seperated, i was running the bike without a fan yesterday ..