nogo1231

my bike is a 96 zx9, and have had no problems with it at all just riding around short distances and such but when i take it on longer rides (20+ mins) it tends to overheat.twice in the past two days it has overheated and i have had to pull over and let it cool off, once was yesterday getting off of the interstate and once was today after i got on to return home.

first time was yesterday, i was headed from the ocean view area out to rosemont and rode the interstate not dogging it at all but getting on it a little, and it did fine stayed at about half temp. all the way to right before rosemont and then it shot up and had to stop and let it cool off. on the way home it stayed cool all the way home about 1/4 temp until i get off the interstate and sit at the light and it goes to 3/4 temp.

today i checked the coolant and added just a little bit and took it out for another ride to see if it was because of low fluid and it was fine, less than 1/4 temp. all the way out to the interstate in front of mt. trashmore where i hit it, again not dogging it at all to pass a car to prepare to exit the interstate and the temp shoots right up to 3/4 following that. i exit the interstate and let it sit for a few mins while im grabbing a drink and get back on to go home and it stay about 3/4 temp all the way until the 264/64 interchange when it shoots up to red and i immediately stop with a little coolant coming from the overflow, let it cool for a min and go to ride home. again as soon as i exit the interstate temp shoots from 3/4 to red and i stop and let it cool to half and before i can get home (3-4 mins) its almost to red again.

btw fan does work so its not the fan

sorry for the long post, just trying to as accurately describe the details,any help is greatly appreciated

boredom

sounds like a radiator or thermostat issue. since i have no clue about bikes idk if they have thermostats although i cant imagine them not, anyhow, try ruling out those 2 things first

nogo1231

has a t-stat, was said to have been changed before the bike was bought but im not 100% on that. would it hurt to just take it out and run it without one to see if it the problem? and if it was the problem wouldnt it be a consistent overheating?
ive heard of people having problems overheating with a bad rad. cap, is this a possible problem?

boredom

possible, yes. an easier way to tell if your thermostat is working properly is to clean it and then put in in boiling water to see if it opens. radiator caps not holding pressure is a possibility, but everyone i have know to replace the cap on a car, replaced the radiator within a few months.

Fabrik8

Could be a clogged radiator core, maybe a thermostat but I'm not convinced. So you're saying it's not heating up (is that what "1/4 temp" means?) and then overheats? Something doesn't really add up here...

s2katin

Have you put more coolant in it anytime soon? You said it was leaking, so you might be low on coolant and that's why it's overheating. Other then that check your thermostat....since it's an old bike do you even have a temperature that actually tells you when it's at like 200 degrees or a needle one like in a car? If you have one that actually tells you the temperature what does it say, my bike has gone to 222 degrees and the fan turns on though, but I had an 08 GSXR.

TATTRAT

sounds like a coolant level issue or thermostat issue. at any rate it is a heap fix. You have not said if there are any noticeable leaks/puddles.

A new thermostat should be pennies in the bucket. Even if it is a core blockage, you can get out cheap, better that then frying your engine.

nogo1231

thanks for all the replies, i am going to attempt to answer everyones questions or clear up any misunderstandings of what i typed here so this may be a long post as well. there are no leaks on the bike at all the reason for adding more coolant was because of it spewing out of the overflow and onto the ground. the temp gauge that i have is a needle type like on a car which is why i was describing it as 1/4 half or 3/4 temp as far as how far up the needle was on the scale.

and yes FABRIK8 you are correct it wasnt really heating up, the temp gauge was staying relatively low, like i said less than a quarter of the way up and then after barely hitting the gas to pass someone it shot to about 3/4 of the way up the gauge. also i know its not the gauge being funny because i can feel a difference in temp blowing on my legs that seems to match pretty well with how the gauge acts.

it just doesnt make sense to me, when i had my t-stat go out in my car it would consistently overheat, but im new to bikes so this could be a possibility.

98formulaLS1

here's what i would do....

1. remove the radiator, since it's small, and reverse flush it with water to clear any gunk that my exist
2. reverse blow out the fins with high pressure air
3. replace the t-stat, it's pennies.

After that, i would look into oil level and spark. If the oil level is low, there isn't going to be sufficient cooling internally. if there isn't sufficient spark then you can get unusual detonation that causes overheating, but i doubt it's that complex right now.

Fabrik8

Bikes and cars really aren't any different in how their cooling systems work, so most concepts that apply to one also apply to the other. Most bikes have the coolant temp sensor on the block, so you should be seeing a fairly good reading of what the temp is as opposed to seeing the temp on the radiator side of the thermostat, etc.

The not getting warmed up properly behavior is what's really got me scratching my head. The only thing that normally causes that is a stuck open thermostat, and then the problem is usually related to running cold all the time instead of regulating temperature properly. Pockets of air in the cooling system usually make all kinds of strange behavior, but if the temp sensor was sitting in a pocket of air it would usually read higher than normal (steam can get incredibly hot) depending on the cooling system pressure.

Regardless, make sure the coolant system is really well bled. The only thing that usually makes the temp behave like a light switch is trapped air. Everything else is a fairly constant problem with constant behavior.

I'm not trying to scare you, but I'm almost thinking you could have a head gasket problem, maybe caused by the previous owner.. That may have been the reason that the thermostat was replaced, but the engine might be permanently warped now.