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2006 Kawasaki ZX-6R Overheating and shutting off

17K views 21 replies 9 participants last post by  Duc995 
#1 ·
I'm fighting an overheating issue on a 2006 ZX6R.

The bike runs 195-210F while moving, however, it quickly jumps into the 230s when idling. It then proceeds to slowly creep up until hitting 240s and shutting off.

I have checked/done the following:
- Flushed cooling system with a hose, then put strong chemical radiator cleaner, rode for 4 hours (as per instructions), flushed again, and put distilled water with water wetter
- Opened up water pump. Propeller is in great condition, free of gunk. When running with the radiator cap off, reving the engine gets the coolant inside the radiator moving fast, indicating to me that the water pump works
- Took out thermostat and put it in a boiling hot water. It opened 8mm as per instructions in the manual. I did not find out at WHAT temperature it opened but it looked to be in good condition and functional. Cold water closed it again, and the boiling water once again opened it.
- Ran the bike with the radiator cap off and revved it till no more bubbles came out (burping the cooling system)
- Verified fan turns on ~210F and spews a CRAPTON of burning hot air on my legs while it idles and overheats. Fan is working and radiator is burning hot to the touch throughout, yet bike temps still keep going up until it shuts off. This is in 70F ambient temperature.

None of these have helped (significantly). I am OUT of ideas on what is causing this much overheating. I do not have a ECU flash or power commander or any mod that would mess with the ECU or fueling. I also have checked that the oil is NOT milky (it is completely normal colored) and my exhaust does not make any white smoke (I don't think it's a blown head gasket). The bike runs very strong and there is no loss of power.

Please help. Frankly...I am considering trading it in/selling and taking a loss on it if I can't figure this out. I love this bike but I can't ride it if it overheats/burns me.
 
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#2 ·
Had a over heating prob. very close to what you are describing with my connie, I bypassed the fan switch on the rad. and added a manual toggle switch, as soon as the bike warms up good I flip the switch, seems to keep it in the correct operating temp range.
 
#4 ·
are you getting any pressure in the system when it gets hot?

squeeze a hose once its up to temp. if its not hard, maybe the cap is bad.
also, be sure you are getting all the air out of the system. it can be difficult sometimes.


I like to fill the radiator, and the overflow, then run the engine until up to temp, then shut it off, and let it cool completely. then rechecked. repeat if necessary.
 
#7 ·
Thanks guys.

I was about to replace the cap last week with a slightly-higher pressured one (20 psi) but friends persuaded me that it won't do anything.
I'll check the hoses for pressure this afternoon. I REALLY hope it's something simple like that...though with my luck, likely isn't.


Wouldn't a bad cap make me LOSE coolant though? If pressure isn't building in the system, wouldn't the bike eject coolant out the reservoir when it's hot?
 
#8 ·
Thanks guys.

I was about to replace the cap last week with a slightly-higher pressured one (20 psi) but friends persuaded me that it won't do anything.
I'll check the hoses for pressure this afternoon. I REALLY hope it's something simple like that...though with my luck, likely isn't.


Wouldn't a bad cap make me LOSE coolant though? If pressure isn't building in the system, wouldn't the bike eject coolant out the reservoir when it's hot?
don't go higher than what it calls for.


it might, but it would have to fill the overflow bottle completely first.
 
#9 ·
When it overheats does water go into the overflow bottle?
If not, it's probably holding enough pressure.
For every 1# on your cap it raises the boiling point 3* so don't go higher than recommended pressure for your system.


Took out thermostat and put it in a boiling hot water. It opened 8mm as per instructions in the manual. I did not find out at WHAT temperature it opened but it looked to be in good condition and functional. Cold water closed it again, and the boiling water once again opened it.

You seem to be running hot at speed so I was suspecting the thermostat. Your stat should be opening sooner than boiling point of water at 212*. I would verify stat is opening sooner than boiling water.
My guess is you still have air in your system since it runs hot all the time or you have a hose collapsing possibly on the inside on the suction side.
 
#10 ·
I keep the overflow nearly full as of the many times refilling the cooling system in the past month.
I did notice it was spewing coolant out the drain hose when I let it idle BUT the overflow was full up to the brink (cold) at that point so I think it was normal. I don't think it's spilled coolant since.

I have a friend with a zx6r so I'll switch caps with him this week and see if anything changes.
If not, this weekend I'm pulling that stat out again. At least it isn't too hard, only remove tank and a few bolts.
 
#11 ·
I keep the overflow nearly full as of the many times refilling the cooling system in the past month.
I did notice it was spewing coolant out the drain hose when I let it idle BUT the overflow was full up to the brink (cold) at that point so I think it was normal. I don't think it's spilled coolant since.

I have a friend with a zx6r so I'll switch caps with him this week and see if anything changes.
If not, this weekend I'm pulling that stat out again. At least it isn't too hard, only remove tank and a few bolts.
if you pull the stat, just go ahead and replace it.

also, boiling isn't a good way to test our stats, as I believe their operating temp is 140*. far lower than boiling...
 
#12 ·
Have any of you heard of thermostats going bad to produce behavior like this though?

From talking with people and some reading, they seem to either go bad stuck open or closed.
I pulled mine already 2 weekends ago and it opened and closed seemingly "normally". Nothing looked broken, corroded, stuck, etc.
 
#13 ·
as you know, the water coming into the engine is cooler, then is heated up by the engine until the thermostat opens and allows the heated water to exit, cool water then come in again and the thermostat senses the temp change and closes...the cycle starts again.
the radiator cools the hot water that exited the motor.

if the coolant cycle has a continuous flow, the water will eventually heat up more and more until the engine overheats.

its seams that this is happening... the cycle is not stopping and the whole system is gradually heating up.

I would disconnect from the radiator the hose the coolant is exiting the engine from and let the coolant run out on the ground, put a water hose to constantly fill the radiator, run the bike to see if it gets hot or not.

I feel either your radiator is not cooling the water, or the thermostat is staying open/close

you will be able to see the flow and check the temp of the output.

the thermostat could be replaced inexpensively enough, but the radiator...arghhh
 
#14 ·
Correct me if wrong but I was under the impression the thermostat stays COMPLETELY open once the bike is up to temp.
It is closed when the bike is cold to allow the engine to warm up fast, then opens and stays open to allow water to circulate through the cooling system and cool it.

Is that wrong?
 
#16 ·
Correct me if wrong but I was under the impression the thermostat stays COMPLETELY open once the bike is up to temp.
It is closed when the bike is cold to allow the engine to warm up fast, then opens and stays open to allow water to circulate through the cooling system and cool it.

Is that wrong?
I do believe that's how our bikes work.
standard automotive engines are different. they use a stat that is much closer in rating to the actual operating temps.

that thermostat opens to let the heated coolant out then closes.

in this manner the coolant stays below "X" temp.

if the thermostat stays open the bike's coolant will slowly increase in temp until boiling over
i think this would be correct, on a vehicle. but our bikes specifically run a 140 degree stat. yet, normal operating temperature is right about 200 degrees. this leads me to believe that once opened, the stat never closes.
I cant see our tiny radiators dropping the coolant 60 degrees in order to allow the stat to close again.
 
#17 ·
Thermostat operation


If the thermostat stays open (as I think it should), the coolant is allowed to circulate through the engine (heated) and then through the radiator (cooled). I don't understand how having a closing & opening cycle of a thermostat is useful in a hot engine.

It should only start to close if the engine temperature is getting cold.
In effect, I see your idea of it opening and closing as the engine warms up and is cooled, but when it is THIS hot (200F), the thermostat should be WIDE open and stay that way to allow the maximum amount of coolant to circulate and cool it. Our thermostats should begin opening at 140F per specification and be fully opened by around 160. Hence...if I'm at 200F, it should be wide open.

Unless I'm VERY wrong about thermostats from all my reading. Someone please step in if so.
 
#19 ·


Permanent type antifreeze is used as a coolant to protect the cooling system from rust and corrosion.
When the engine starts, the water pump turns and the coolant circulates.
The thermostat is a wax pellet type which opens or closes with coolant temperature changes. The
thermostat continuously changes its valve opening to keep the coolant temperature at the proper level.
When coolant temperature is less than 55°C (131°F), the thermostat closes so that the coolant flow
is restricted through the air bleeder hole, causing the engine to warm up more quickly. When coolant
temperature is more than 58 ∼ 62°C (136 ∼ 144°F), the thermostat opens and the coolant flows.
When the coolant temperature goes up beyond 95°C (203°F), the radiator fan relay conducts to operate
the radiator fan. The radiator fan draws air through the radiator core when there is not sufficient
air flow such as at low speeds. This increases up the cooling action of the radiator. When the coolant
temperature is below 90°C (194°F), the fan relay opens and the radiator fan stops.
In this way, this system controls the engine temperature within narrow limits where the engine operates
most efficiently even if the engine load varies.
The system is pressurized by the radiator cap to suppress boiling and the resultant air bubbles
which can cause engine overheating. As the engine warms up, the coolant in the radiator and the
water jacket expands. The excess coolant flows through the radiator cap and hose to the reserve tank
to be stored there temporarily. Conversely, as the engine cools down, the coolant in the radiator and
the water jacket contracts, and the stored coolant flows back to the radiator from the reserve tank.
The radiator cap has two valves. One is a pressure valve which holds the pressure in the system
when the engine is running. When the pressure exceeds 93 ∼ 123 kPa (0.95 ∼ 1.25 kgf/cm², 14 ∼ 18
psi), the pressure valve opens and releases the pressure to the reserve tank. As soon as pressure
escapes, the valve closes, and keeps the pressure at 93 ∼ 123 kPa (0.95 ∼ 1.25 kgf/cm², 14 ∼ 18 psi).
When the engine cools down, another small valve (vacuum valve) in the cap opens. As the coolant
cools, the coolant contracts to form a vacuum in the system. The vacuum valve opens and allows the
coolant from the reserve tank to enter the radiator.
 

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#22 ·
If everything you have tried doesn't work, you really need to rule out a bad head gasket. If you have coolant circulating - implying a functioning water pump, no air-locks, an open thermostat at temp, a functional radiator, and correct pressurization - the only thing left is head gasket failure. If coolant is truly circulating, the fan coming on HAS TO make the temp drop; if it doesn't drop then coolant isn't flowing through the radiator. I'm dealing with this same issue on a '12 zx6r and my next step is to pressure test the cooling system. If there is a sign of a pressure leak/drop then I'll have to look in the cylinders through the spark plug holes with a borescope to look for a coolant leak since I have already confirmed no oil in the coolant, or any coolant in the oil.
 
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