Hi i have a yamaha xmax 250cc & have coolant pushing way way back out of the exspanion tank and although this coolant is not hot the Temp gage show bike to almost in red but fall quickly but changed to sender for gage with new located at top of enging also new rad sender switch, my main worry is could be head gaskit but there no oil and water mixing or smoke

Sometimes when you open cooling system, air gets in, it can cause problems with temp gage.
How hot does it get in degrees F? Is the coolant boiling over? Are you losing coolant? Use a non-contact infra red temp gun to take engine temp, At least we will have a degrees F reading. Most temp gages say hi or lo, cold or hot. I don't know about yours?
Can you check for combustion gases in the coolant?

What about the radiator? Water pump? Can you check for coolant flow? There could be air in the cooling system? Do you trust your temp gage? Are there overheating issues besides the temp gage showing hot, like coolant overflowing, under the hood, somewhere?

natural for engine temp to rise in Traffic - Until Themostat opens ) cooling fan sensor kicks on fan . But Antifreeze is not just a Cold weather item . Coolant is Absolutely Necessary for Hot Days . You must be full to recovery bottle setting of cold when checked prior to start up . Coolant for your make / model is Reddish - Pink colour and should have a reading of -25 thats negative 25 degrees the Lower the Better even - 50 .. Why ?? - 50 is 50 %% antifreeze / Coolant Concentrate MIX Gives Hot weather cooling Ability or very cold weather starting / winter HEAT .

Could be.
Are you sure the radiator is full, and are the heater hoses getting hot ?

Do you have a temperature gage in your instrument cluster? When the temp goes cold, does the temp gage rise? Check your coolant level both in the radiator and the coolant recovery tank under the hood, and fill as necessary. If that is OK, then check your serpentine belt for wear and/or slippage around the water pump. Lastly, if you have a temp gage and are noticing fluctuations in the reading, you may need to replace your cooling system thermostat. Good luck.

If the temp gauge periodically rises higher than normal and then falls back to normal, you probably need to change the thermostat as it may be sticking shut and then popping open. It's a good time to change some hoses, coolant and check the belts if they've been on the car for awhile.

Please click this LINK to read a great article on causes and fixes for overheating problems. I can't post it due to copyrighting. Also DO NOT RUN THIS ENGINE WHEN IT STARTS TO GET HOT YOU WILL SEVERLY DAMAGE IT.

the first thing is to check the coolant level, if coolant is full you may have a bad thermostat or a bad coolant temp sensor,when it runs hot, the best way to determine if it is hot is to check the temp at the sensor with temp checking tool.

Hi There
I have had the same problem, if the climate control shows different temps at either side it most possible that the heater valve needs replacing, the valves inside get rusty and sieze up, it is situated at the front o/s at the side of the radiator. If temps are the same could be the control module

Did you bleed the air oout of the cooling system - Their is a bleeding next to the therostat housing.


1 - When the vehicle is cold remove the rad(tank) cap and top up the level if needed

2 - start the vehicle with the rad cap off and leave the car run until you can see that the therostat has openned(look in tank/rad) to see fuild flow then open the bleeder slowly to let any air out of the cooling system. Once you have coolant flowing out of the bleeder close the bleeder and install the rad/tank cap.

NOTE - Be careful with the engine running and hot Coolant.

You make need to bleeding system 2-3 time to get all the all out. Once all the air is out of the system you problem should be solved. If air returns to the coolant system have the system checked for possible head gasket leaking air into the coolant system