Sorry help needed with my winter hack!

[Acidicall]

Ok so now its cold icy and sh*t i put the storm away and get the piaggio x8 250 (yes i know embarrassing) out for work. It has got a problem that i really cant get my head around so thought i would ask you guys for some help!

The bike has not been used for a good couple of months and i ran it for the first time to find it overheating. The problem is the coolant has no air bubbles in the system, i have checked, the temp gauge goes all the way up to max and the fan does not come on. So i unplugged the thermostat wire, started her up and the engine management light came on (like i thought it would) and the fan came on! So i know the fan now works. plugging back in the thermostat wire the engine light goes out and with it the fan turns off even tho the gauge says red hot still?

So is the thermostat buggered and not opening etc or sending correct signals, even tho it is telling the gauge it is hot? or is the gauge buggered and the bike is not as hot as its saying and that is why the fan is not on?!

So im sorry this is a non-vtr question but could do with the help!!

[fabiostar]

id be checking the thermostat first incase its stuck having been sitting around doing nothing. at least it rules it out.

[Acidicall]

ok well i started her up again and started tapping at the thermostat to see if that would move it if it was stuck. Noticed as she got warm that the exit hose from thermostat to the rad was getting hot, but the inlet hose from rad to water pump was cold. bike started overheating again and the inlet hose was still cold, where the exit hose was very hot. This is telling me that the thermostat is opening (as the exit hose would only receive hot coolant if this was the case) but the water pump is not pumping through the system allow the cool coolant from the rad to do its job. I also think the fan is tiggered by a sensor on the rad (think i saw this when the bike was stripped last time) due to the distance between engine and rad the designers probably thought this was a good idea. So fan wont cut in as the rad has not got to temperature.

So this means the water pump is buggered. But how can i check the water pump to see if that is the problem, or do i just replace?

[Wicky]

Hot water test thermostat

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[mayfay]

Hello you dident say how long engine needs to run befor the gage sayes its overheating, when it dose say its overheating put a good rag over the cap to remove and see what happens, if it is overheating you'll know. If its got an exspantion tank is that Hot and full.

[lowside]

I would put money on the thermostat being stuck closed, not allowing water to pass through the radiator. Conduction will cause the top hose to get hot, but if the rad and bottom hose are cold then water is not circulating. Even if the water pump was not working the system would still thermosyphon and circulate slowly through the rad.

[fabiostar]

what he said ^^^^^^^^

[Acidicall]

Thanks for your Posts i have taken out the thermostat and tested it. It was opening but at around 100 - 105 C, So the bike was not overheating (but the scoot was at max on the gauge, so probs not good) i have removed it and the bike runs fine, maybe a little cold due to the cold weather but i guess that better then hot! i will get a new thermostat soon. The fan still wont turn on when it should so the remote switch must be dead? or would that be the thermostat sensor?

At least i can use it for work for the time being