Trouble with overheating... - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
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post #1 of 7 (permalink) Old 07-26-2013, 12:30 AM Thread Starter
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Trouble with overheating...

Having a continuing problem with my cooling sytem. The bike runs very hot, gauge shows the needle close to the white line before it hits the red zone but always stays there or right below. When I do turn off the engine, I get an overflow of coolant on the ground. I can hear the coolant bubbling inside the expansion reservoir, I can't believe this is proper. I've flushed the radiator, installed a new stock thermostat and replaced the radiator to reservoir line in case there might have been a leak at some point. I've followed Clymers directions on filling and bleeding the system but I'm not 100% sure that there is not air still in the system. I've read over the notes in the Verses but there isn't much help there as far as step by step or pointers.
After searching the forum I am guessing the problem stems from one of the following...
1. Air still in the system
2. A bad Radiator cap (someone suggested this might be a problem in a post somewhere)
3. A dirty/corroded passage somewhere

Please offer any advice and pointers, any suggestions, opinions or past experience would be greatly appreciated.

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post #2 of 7 (permalink) Old 07-26-2013, 12:50 AM
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It's possible that there may still be a little air in the system, but it sounds like you did a pretty good job bleeding it. I would start with flushing it out and inspecting the seal on the cap if it's worn it could need to be replaced. They're not cheap, but if it solves the problem, worth every penny.

There are other possibilities like a malfunctioning fan out even running lean both if which could make the bike run hot. I believe that the fan should come on somewhere between half and three quarter on the gauge. To see if it's running lean, do a spark plug check. That can tell you a lot about what's going on in an engine.

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Last edited by Jakzen; 07-26-2013 at 12:57 AM.
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post #3 of 7 (permalink) Old 07-26-2013, 12:59 AM
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4. stuck thermostat (have seen a lot of defective new thermostats also)

Remove the t-stat, boil in a pan of water with a thermometer and see if it opens near the specified temperature, then closes as it cools. Run it through a few cycles. The rated temp should be in the manual. Should be somewhere around 180 to 195.

This would also prevent getting all the air out of the system.

When I refilled my radiator, I just left the cap off with the bike idling until the coolant expanded into the filler neck, to get the air out. I didn't use the bleeder valve.

5. Does the fan run?

6. You could have the radiator flow tested to see if it's clogged. (radiator shop)

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post #4 of 7 (permalink) Old 07-26-2013, 08:24 AM
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Sounds like a stuck thermostat or possibly put in upside down. You might have an air block. I bleed my system after the engine is warmed up and running. Use the air bleeder valve like you would bleeding brakes. You do not have to remove the tank, just the side cover and use a longer 10mm wrench.


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post #5 of 7 (permalink) Old 07-26-2013, 10:01 AM
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My fan comes on just before half on the gauge.
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post #6 of 7 (permalink) Old 07-26-2013, 10:32 AM Thread Starter
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Thermostat is brand new, installed correctly with the bleeder hole positioned upward. The radiator has been flushed and gone through. The fan does kick on at the right time, no problem there. I need to check my plugs for sure but the bike seems to be running rich if anything. I'm leaning towards radiator cap replacement.
Thanks a lot fellas.

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post #7 of 7 (permalink) Old 07-26-2013, 10:55 AM
..have a vulcan good day!
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Originally Posted by wmsonta View Post
My fan comes on just before half on the gauge.
...that seems about right.
My fan turns on @ little over half (say 65%) on the gauge.

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