[fast_eddie]

97 ZX11D which is running hot. As in, it gets up to operating temperature, does fine on the highway, but as soon as I get back down to 30mph stop/start driving or even worse, traffic jams, the fan is running almost constantly and the temp gauge needle climbs up to a little over halfway. I don't recall it running this hot before. And this is in the relatively cool (40s to 60s deg. F) weather recently.

I recently refilled the overflow reservoir which was very low; I'm not smelling any coolant when I'm riding it though. There is no water in the oil, and my oil level is normal, so I don't think there's a cracked jacket. I swapped the radiator cap for another identical one but it made no difference. The fan is coming on, which I believe means that the thermostat is working, since the fan switch is located on the bottom ("out") side of the radiator. I replaced the fan switch last year when it failed which is the last (only) time I messed with the cooling system.

My guess is that the water pump is not functioning or only partially functioning, which is leading to the water circulating very poorly or not at all. Before I replace the water pump (I have a spare donor bike I can try before buying a new one) am I overlooking anything? Any suggestions what else to check?

Cheers

 

[Blainethemono]

Thermostat - when the bike begins to heat up check the temperature on BOTH hoses. Bad thermostat will have 1 hose extremely hot, the other warm @ best... Means Thermostat is not opening and water is not circulating.

 

[fast_eddie]

Thermostat - when the bike begins to heat up check the temperature on BOTH hoses. Bad thermostat will have 1 hose extremely hot, the other warm @ best... Means Thermostat is not opening and water is not circulating.

K thanks.

As far as testing the thermostat, I've done the drop it in hot water test, but where can I find what is the actual temperature range it should open up at?

 

[KevA]

Thermostat must be opening as the Cooling fan is cycling.
Have you made sure the Radiator cooling fins are not clogged reducing the airflow being drawn through the Rad by the Fan.
Also a weak mixture will cause the Motor to run hotter, This could be down to the carbs or an Air leak.
When were the valve clearances last checked ?

 

[Blainethemono]

Thermostat must be opening as the Cooling fan is cycling

the fan is running almost constantly and the temp gauge needle climbs up to a little over halfway

Im going by this and this is not the fan cycling.....This is the radiator being one hot MF'er, which to me means water to NOT moving thru the system. lol

I also have seen thermos work just fine in a pot of boiling water and fail in practice. Its easy enough to pull the Thermo & run it w/o it, so we can remove it from the equation once and for all. Hell, I went thru two of those bastards b4 I got one that worked in my Prelude. They DO NOT make them like they used to.

 

[fast_eddie]

Im going by this and this is not the fan cycling.....This is the radiator being one hot MF'er, which to me means water to NOT moving thru the system. lol

I also have seen thermos work just fine in a pot of boiling water and fail in practice. Its easy enough to pull the Thermo & run it w/o it, so we can remove it from the equation once and for all. Hell, I went thru two of those bastards b4 I got one that worked in my Prelude. They DO NOT make them like they used to.

Thanks Blaine, I will pull the thermostat and see what difference that makes. If I find that it is not running hot under similar conditions I will be able to conclude it is the thermostat and not the water pump that is faulty.

I'm guessing it's actually pretty rare for the water pump to fail anyway.

 

[Blainethemono]

Its easy enough to check. My 28 year old ZX-11 has 70k on her and is still running the OEM water pump. Sure they can fail, but Kawasaki makes their their water pumps like they make their alternators & clutches. ROCK SOLID, built to last.... after all, they have been playing the high edge of the Horsepower race for a long time and they know what breaks.

 

[Hammerhead]

Cooling system may have some trapped air. Follow the burping drill described in your shop manual

 

[The Heater]

Before you blame parts or equipment, take the time to perform normal periodic maintenance that could solve the problem

1) completely drain system. Flush out twice with clear distilled water (not tap water). 2) go to Myler's Radiator Repair web site (they repair motorcycle radiators), buy a couple of bottles of their cooling system flush, follow instructions and flush the system, then again run distilled water through to clear it out completely. 3) remove thermostat. place in a COLD saucepan with water and a cooking thermometer. Watch the temp rise, note temp that it opens. If this is not the temp range specified in your service manual then replace the thermostat. This will not be the overheating issue unless it is opening at a temperature substantially higher than that specified in the service manual. 4) remove the temperature sensor from the radiator for controlling the radiator fan. Again, place in a sauce pan with COLD water and a cooking thermometer. Get a Volt-Ohmmeter or Multi meter set for resistance (10,000 ohms for example if it has a range), connect the leads to the wires from the sensor. Watch the temperature on the thermometer, note temperature at which the switch closes. This is the temperature it turns on the fan (ohms go from infinity resistance down to some value of ohms resistance when the switch closes). 5) Use Water Wetter or equivalent in your coolant if you want some additional cooling performance from your coolant. However, this does not solve overheating issues. If after all of this, and any part replacements you have confirmed through the testing I have specified, you still have overheating, I would consider the age of the bike and maybe send the radiator to Mylers and have them clean and rebuild it for you. If you don't want to do that, you could consider replacing the water pump, but if the bike works at highway speeds the water pump probably is fine. You could spend the money and replace it anyway if you have money burning a hole in your pocket, but I honestly think if you try what I suggest here, you will solve your problem. The last thing I would consider would be a head gasket leak but you will have other symptoms that you have not mentioned if that were the problem. You also could have low oil level but I am assuming you checked that and the oil is topped up.

Myler's Miracle Radiator Flush

Myler’s "Miracle Flush" is a concentrated radiator flush specifically formulated to remove clogging hard water deposits in motorcycle and snow mobile aluminum radiators. Annual usage will eliminate the detrimental effects that hard water has created in your radiator, thus restoring peak cooling...

www.motorcycleradiators.com

 

[Blainethemono]

Ya know, might as well Get 'Er Done now instead of redoing labor later. I did this about 8 years ago, its major Piece of Mind stuff..

R&R ALL the radiator hoses, they are over 20 years old, then you can run water thru every orifice of that bike to make sure all passages are clear of obstruction. Check the fuel lines at the gas tank as well. I replaced mine about 6 years ago.

Dont procrastinate, JUST DO IT!!

P.S. this is a kool mod full write up

 

[fast_eddie]

Cooling system had a good flush last summer when I replaced the fan switch. This time out I pulled the thermostat and checked the operation.

Shop manual says it's supposed to open btwn 80-84degC, to a maximum of 8mm. It didn't even start to crack before 88C and got to maybe half of the 8mm max, so I've got a new one on order. In the meantime, I put it all back together sans thermostat so I can keep riding. Thanks for the tips fellas.