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Discussion Starter #1
I am in trouble.
Tonight I wanted to check the oil level. So I left the bike on for about 20 minutes. At some stage I saw that the bike was steaming, looking closely I saw the coolant boiling in the compensating tank. Temperature was 122! Switched the engine off and as soon as I did it a huge amount of pressurised steam came off the from around the water pump/hose or perhaps was coming from the cooling sensor/thermostat of the front cylinder.
When turning the keys back on the fan is not working. Checked the fuse and it was blown. Replaced the fuse still not working. All wiring seems to be plugged in.
Dash says Sensor Error which I believe it means that there are different temperatures between front and rear. When I tried again at cold engine that was gone.
I recon I switched the engine quite quickly. It might have been running at that temperature around 5 minutes.

POSSIBLE CAUSES:
Radiator thermostat failure? (but why would have it blown the fuse?)
Fan failure?

DAMAGES
Water pump gasket?
Hoses?
Cylinder water connection plug?
Cylinder Temperaturen Sensor?
Engine???????

What shall I do now? How to test Thermostat and fan. And even when I find the cause what shall I replace?

Thanks

Nic

35165


35166
 

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The thermostat you can test with a meter. The fan is gonna be 12v so could possibly wire directly to battery...

Sent from my SM-N950F using Tapatalk
 

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KTM RC8
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Can you move the fan round by hand? Mine jammed on another bike because a twig was stuck in it, the torque stall of the motor blew the fuse.

I would fix the fan first, then see what happens from there. You could bridge the connection where the relay plugs in. Check wiring diagram.

When mine was leaking it had an airlock but the fan still kicked in so it never got as hot as yours. Hopefully all is OK and you didn't lose too much coolant, but if topping it up again then bleeding is a pain, as you need to raise the front by 50cm to get the air out.
 

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this bike doesnt run a thermostat, from what i remember its an open loop system. if it was showing 122, the sensor must be working. id assume the fan to be at fault, especially if the fuse has blown. do as suggested and check the movement of it, and then jump it with a battery directly.

damage could be bad, or could be nothing.
 

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KTM RC8
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Kind of correct, not 'a thermostat', but two thermostats, both 70 degree C rated. It's possible if jammed shut they would cause overheating but as the fan was not working it must be the primary issue.

There's also one thermo switch that clicks on at 102 degrees. If this was broken then the fan wouldn't come on, or would be on all the time.

The temperatures mentioned are listed in UK spec 2009 bike on Fowlers.
 

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just looking at those pictures again, there looks like a lot of coolant over the engine. could well be that gaskets have blown, especially if you switched it off at that temp. i would be very cautious about starting it up again until you get it looked at, i would worry that the head gaskets have gone and coolant has spilled into the cylinder. if you try to start it, you could bend a rod if it doesn't just hydro lock from the start. potentially a write off engine, with all the inspection work needed. unless you're going to do that work yourself?
 

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Check the fan can rotate, push it around by hand. mine siezed due to water in the bearing. had the same effect, and blew a fuse.
 

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The easiest way to test Rad Fan is to bridge Themoswitch but check Fan for free movement first if the fuse blows it is more likely the fan there is 2 coolant temp units on the RC8 one on each cylinder and on mine fan use to kick in around 106 degrees C U could also check thermoswitch terminals for insulation failure but I doubt it fuse would blow as soon as U switch ignition on (y)
 

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These older types get the fan starting only @ 108°C
The later types start @ 95°C.
What very worying is, the fact that when the sytem hits 105°C , the fuel systems gives signal to jet less fuel, so the heat goes up quite fast. Dunno what the engineer at KTM was thinking that day. These can't be fixed with tunecu of tuneboy.
I can only recomand to go for a RC8R thermostat, or use a switch to turn the fan on and off.
 
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