07 250 overheating after highway speeds or idling

[dood59]

hi! I have a ninja 250 2007 with 5,000mi. A few weeks ago the screw that holds one of the coolant lines coming off the water pump came off and it dumped coolant all over the highway and temp got into the red. I got a new screw and attached the line, filled the coolant, I have let the bike warm up several times and topped off the coolant until the radiator is full and resevior is at the full line. The bike is now overheating after idleing for several min or when I slow down from highway speeds( i can hear boiling in the engine block at this point).. it is fine while I am moving. The fan seems to come on close to the redline and cools it a little but shuts off after about 30 seconds a few min later it will come on again for about 10 sec then the bike overheats into the red. Until the line came off the bike, it has never gone past 12oclock on the temp guage (even in traffic on 100 deg days)and fan used to come on around 1 oclock. Anyone have any ideas on what to check and in what order? Dealer wants $90 an hr for diagonistics and i have no job..

[bob706]

Welcome to the forum. Sounds like the waterpump is gone.

[dood59]

hi and thanks for the welcoming, do you know of any way to test the waterpump?when i open the radiator cap and run the engine, it looks like the water is just vibrating and not flowing. im going to test the thermostst today in a pot of boiling water.

[rockNroll]

Your symptoms are typical of not having the cooling system full and/or a blown head gasket.

You think the radiator is full and the jug is to full level. Now... when the bike is "overheating" is there coolant leaving the radiator and adding to the jug's level?

[dood59]

yes and no..as it overheats and boils, the coolant overflows out the tube down the middle of the bike , but the level in the coolant res stays at the max line.(does not suck any back into the radiator). whatever spills out, i can add that amount back into the radiator??..the bike is not smoking and oil in the motor is not milky and runs normal and idle is normal.. are there any bleeder valves or plugs i could try opening to help get rid of an air pocket if there is one?

[JMcDonald]

I was going to say it sounds like a leaking head gasket, if the coolant level is not low and the system is correctly primed. A leaking head gasket can also result from overheating in general.

[sombo]

J.. a leaky gasket would cause the level to drop as the coolant would escape into the combustion chamber and be turned to vapor.

From the last post from the OP it sounds like what happens in a car when the thermostat is stuck or when the pump isn't working. Basically it means you have no water flow. When you lost all of your coolant on the highway it might have fried your pump. Water pumps working with no water will burn out quickly because they are designed for the resistance. If there is no resistance they tend to go poof.

[JMcDonald]

Good point about the t-stat. That has actually happened to me bedore on an older car. However, if it were stuck closed, the bike would also overheat at high speeds. Also, Ive seen blown head gaskets only cause a very slow reducton in flUid level, while still causing overheating due to the combuston gases leaking into the coolant system.
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[sombo]

Well bikes are a bit different then cars at high speed. If you notice, our engines have a small amount of heatsink fins on them. As you go up in speed more air flows over the motor helping in the cooling of the engine. This is what helps allow for smaller cooling systems and also why they tend to overheat when not moving. The cooling systems they use are designed with that bit of air-cooling in mind and therefore have more trouble cooling in slow traffic then cages do.

[Alex]

I'm not sure sombo; everything I've read about the few cooling fins on water-cooled engines like ours are that they are for styling alone. Without them, the engine would look more like a water pump than a motorcycle engine. The only thing that is truly doing any cooling at all may be the radiator. But to your point, even the radiators on motorcycles are sized such that it is assumed the bike isn't going to be sitting still indefinitely, and it does need to have reasonable airflow by being in motion to effectively cool the engine.

[dood59]

Thanks guys!!! ... at this point I think I'm going to change the waterpump because I tested the thermostat and it opened when I boiled some water! After changing the waterpump is there anything I need to know about filling , primeing and bleeding the system so I can be sure it is not an air pocket? And how would I check for a bad headgasket?

[kkim]

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

http://faq.ninja250.org/wiki/Cooling_system

[jeffsiri]

@dood59

The exact same thing happened to my ninja 250 where the screw came off the coolant line and dropped coolant all over the highway. Now my ninja heats up at low speeds or idling past the 12 o clock mark but does perfectly fine on highways staying under the 11 o clock. Did you figure out the solution to your problem?

Hopefully you get to this post even though its old!

[dood59]

Yes I was able to fix the problem. After changing the thermostat, with no success, I ended up changing the head gasket and that fixed the problem. Not a hard job to, just be cautious when setting the timing. I used a book that had a typing error in it and ended up having to buy a cam and a rod and a different manual. I also recommend doing the valve adjustment while you have it apart. Put about 5k on it since then and sold it to someone who sent it to Russia. I have the shop manual still if you need one. Let me know.

[jeffsiri]

Awesome thank you!

Did you end up having to change the water pump at all?

[omarcarbomb]

my lower water pump bolt came off on while riding on July 4.
The bike hit the red (which it never does) so I pulled off the high way. I was not sure what the problem was but when limped off the highway the temp went down. Then I heard the water pump run empty and clatter so I pulled over and parked it.

The bike sat for 3 hours while I went home and got coolant and a bolt.
Came back and filled up bike and road home. Bike was warm when I got home and the fan engaged for a bit when I came to a stand still in garage.

The next day the bike is now running hot like other posts above but with one additional difference. The fan will not come on even though the temp gauge get up to the red line. I tested the fan manually and it works.

since the temp gauge is at the thermostat and the fan switch is on the radiator either the fan sensor has died or the hot water is not getting to the fan sensor.

I will let it cool and start testing parts.

I question the riders that are jumping to head gasket failure. The bike runs fine it is just hot and a failed gasket would not explain why the fan is not coming on now. Morel likely the pump is bad and the coolant is not circulating to get to the fan sensor.

These symptoms after loosing and replacing coolant seem common. I have found many riders posting with very similar problems after losing coolant.

[Motofool]

Originally Posted by omarcarbomb

......... since the temp gauge is at the thermostat and the fan switch is on the radiator either the fan sensor has died or the hot water is not getting to the fan sensor.........

If the level of coolant inside the system is too low, the fan's sensor is in a pocket of air rather than submerged in the hot coolant.

A milky color of the oil will tell you if coolant is leaking trough the gasket.
Sometimes, oil can see floating in the coolant through the radiator's cap.

Take a look at this:
http://faq.ninja250.org/wiki/Cooling_system

[dood59]

@omarcarbomb It has been a few years since then. If my memory serves me correctly, I believe I used some kind of device and chemical to tell if I had exhaust gas in my coolant that my buddy who owns a shop had. I believe It sells for about $50 and i did change the water pump just in case.

Here is an example. Hope it helps! https://www.google.com/shopping/prod...BvxvT4AfbTu4gE

[jkv45]

You most likely have an air pocket in the system.

If you fill up the radiator from the filler neck, then start it up (cap off) and run it briefly, most likely the level will drop. Then fill again. When the level starts to rise (spill out the filler neck), shut the engine off and replace the cap. Make sure the overflow bottle is up to the proper level.

If the level in the radiator drops again you will see the level in the overflow bottle drop as well.

[xXecuterXx2]

this thread is like a zombie

[jkv45]

Originally Posted by xXecuterXx2

this thread is like a zombie

Got that right.

Hopefully he has it sorted by now. The original post is from Dec 2010...