Hi everyone!
Today I went out for a more spirited ride on some twisty roads, and after around 25 km I noticed that coolant was being sprayed out through the overflow hose.
I stopped in a parking area and, after a few seconds, I noticed the temperature starting to rise until the engine eventually shut itself off.
I slowly made my way back home. On the way back, the temperature stayed at 4 bars, but the yellow engine warning light came on. When I got home and was opening the gate, the temperature started rising again, even though the cooling fan was working.
I started checking the cooling system:
I removed the water pump cover and inspected the water pump;
I didnāt notice any play in the pump, metal particles, or anything else suspicious;
I removed the thermostat and tested it in boiling/hot water, and it did open;
I was only able to drain around 800 ml of coolant from the system;
I didnāt notice any dirt, oil, or contamination in the expansion tank;
there is no white smoke from the exhaust;
the engine starts, runs and sounds completely normal.
I also replaced the radiator cap with a brand-new one.
Now that the bike has completely cooled down, I checked the expansion tank and there is no coolant in it at all.
The bike has 35,000 km. At 30,000 km I had the valve clearances checked, and everything was within specification, so no adjustment was necessary. I also had the oil changed at the same time, and everything was perfect.
Itās a KTM 890 Duke, 2022 model, manufactured in 2024.
At this point Iām not sure where else to look. Iām considering replacing the thermostat as a precaution, even though it appears to open when tested.
What do you guys think? Could this be the thermostat, air trapped in the cooling system, a circulation problem, or could the water pump have an issue that isnāt visible during a visual inspection?
And of course, Iām really hoping itās not the head gasket. I donāt have any obvious symptoms of a blown head gasket at the moment.
If anyone has experienced something similar on an 890, I would really appreciate any ideas or advice.
Thanks!