Temperature gauge dodgy / overheating / leaking coolant

[Sam2kk8]

Hi Guys,
I have tried to search around this and I've seen a few suggestions on it but wondered if anyone could pin point it more.

I've had this 94 zxr400 for 4 days now and every time i park up i come back to a puddle of coolant. the first time i took the water bottle lid off a load of coolant just kept running out, i let it all run until it stopped then the next day i took the lid off again and even more kept running out.

The temp gauge can also at times reach 3 quaters of the way to hot and then suddenly drop to a quater and seems like its moving about all the time (literally talking it will drop a bar within 2 seconds)

I do hear the fan (cant remember exactly at what point it comes on) but when i sometimes turn the bike off the fan still runs for a while

Ive been into cars all my life but have no clue about bikes so if you could reply simple for a amateur like me

Thanks.

[banner001]

it sounds like your head gasket has gone, but its not necessarily.

first you need to drain and flush your entire coolant system to get out any crap thats been sitting in there for the last 19 years. there is a drain screw at the bottom of the water pump and 2 drain screws under the exhaust headers to drain the cylinder block. drain all the coolant, then put the cylinder head drain screws and the water pump drain screw back in and fill the system with water, drain all this and do this a few times, now go any buy some 50% premix coolant for aluminium radiators (this ensures its made in deionized water - wont rust nearly as fast as tap water), also make sure you drain any coolant from the expansion bottle and its lines.

you are gonna need ~2.5L of coolant to fill the system, fill the radiator first with the bike on the sidestand, when its full fill the expansion bottle halfway between the max and min lines, make sure all your pipes are connected, and then squeeze all the rubber radiator lines to get air out, top up as necessary, then with the rad cap off, fire the bike up for ~2 seconds, this will engage the coolant pump and start to push any remaining air out of the system, topup as necessary...the bubbles should stop...if they dont then you have a HG leak and you need to get that fixed before you wreck your bike.

also if you overfill the expansion bottle it can lead to coolant leaking out if you are really revving the bike.

the temp gauge might be indicating that the sender unit is faulty, but if the fan is coming on then it indicates that the coolant itself is getting hot (different circuit the fan and the temp gauge), the fan sometimes runs for a while in order to cool the coolant down in the radiator - most likely to happen in summer after giving the bike a thrashing.

the temp gauge rising then falling indicates 2 things, you might have a faulty thermostat thats not opening properly, or that you have air in the system.

let us know what your findings are.

[Sam2kk8]

I believe the problems now solved..

i did take it to a bike garage for them to look at.. the coolant hose that runs under the carbs to keep them warm in the winter had been removed and just rerouted back into the expansion bottle causing it to become so pressurized that it forced out the cap of the bottle and started leaking..also it was starving the rad of water causing it to overheat slightly and was getting filled with air (presuming this was why my gauge was so dodgy).

ridden it about 30 miles now and no leaking, no smell of burning coolant and no over heating, so seems to be good for now..

what the twat did who i brought i bike from i dont know!

Thanks for replying banner!

[banner001]

aye, that will do it

i would still give the whole cooling system a damn good flush out...it will be full of old stinking coolant as noone ever changes it...just keeps thinking it can suffer abuse for years and years