Coolant Leak

FaNaTic said:
No. Never remove it.
The bike has 4000 km.
Just change the cooling liquid for water due to racing rules.
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Probably good that it was at the races and only water, or it may have been very slippery for your back tire or anyone behind you.

On my 401 the hose to the thermostat got a leak too, which is why I put samco hoses on it.
 
Thanks for the advice, I’ll put Samco hoses too.
I have check : no water in oil or the opposite.
Maybe the races season last year that weakened it.
 
FaNaTic said:
No. Never remove it.
The bike has 4000 km.
Just change the cooling liquid for water due to racing rules. Maybe bad bleeding.
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Today I changed the coolant on my 701 Svart. Surprising how long the engine needed to idle until the thermostat fully opened and released all the air. The lower boiling point of water and an air bubble left in the system could have blown the hose on your bike. Better a blown hose than an blown head gasket and better water on the track than coolant.:geek: Good luck for your next race!
 
I fixed it last week with an OEM hose. Everything seems to be ok.
At the fifth bar of temperature, the fan starts and stops when it goes down to the fourth bar. Is it the same for you?
The Samco hoses are somewhere on the way.
I will test Wednesday for a track day and if all is OK, first race of the season at the end of May.
Thanks for the good luck.
 
FaNaTic said:
I fixed it last week with an OEM hose. Everything seems to be ok.
At the fifth bar of temperature, the fan starts and stops when it goes down to the fourth bar. Is it the same for you?
The Samco hoses are somewhere on the way.
I will test Wednesday for a track day and if all is OK, first race of the season at the end of May.
Thanks for the good luck.
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Most important when bleeding a closed cooling system is to have the radiator cap open and run the engine at idle. You will see that some bubbles will come up. At a certain point, (four bars in my case) the thermostat will open and an huge amount of air will escape. The coolant level in the radiator will drop significantly and fluid needs to be added. Then you close the radiator cap and the expansion tank at max. level is reconnected to the closed system. Shut the engine and watch the fluid level in the expansion tank. If the system is working like it should, the level will drop from max close to minimum when the engine cooled down. If you followed those steps all should be fine. Go for a ride and check the fluid levels one more time on the the cold engine. Radiator should be still full and the expansion tank approximately 1cm over minimum level. If not top up. I think this is the safe way. It’s a bit messy but outdoors with a large bowl it’s not a problem and coolant drops can be washed. And yes my fan also cuts in @ the fifth bar. Ride safe!
 
Thank you for your advice. I applied the Husqvarna procedure.
Unfortunately, my test this morning lasted only 10 laps. All cooling water goes into the expansion tank.
It's clearly the head gasket that is failing.
I’ll have it changed but it’ll be too late for the first race in two weeks.
I’m gonna ride with my old 690 Duke.
 
FaNaTic said:
Thank you for your advice. I applied the Husqvarna procedure.
Unfortunately, my test this morning lasted only 10 laps. All cooling water goes into the expansion tank.
It's clearly the head gasket that is failing.
I’ll have it changed but it’ll be too late for the first race in two weeks.
I’m gonna ride with my old 690 Duke.
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Oh no! Is the coolant/water coming out the overflow tube?
 
As long as the radiator cap works, and the fluid was not too full than it does point in that direction... is there black carbon inside your cooler?
 
After my last ride I also saw some fluid marks on the ride side of the bike from the front (cooler) till the exhaust muffler. First I thought that I was running through something but then I recognized that my expansion tank is over max level (even with cooled down engine).

Do you have some advices for me? E.g. what should I check/try next?
 
When I bought my bike the reservoir was filled to the max, on the first ride, the bike leaked coolant from the top of the reservoir. The level dropped to about halfway up the reservoir. Then it stopped leaking. At the first service, they topped it up to max. It spat it out on the way home.
Then stayed at half full reservoir without leaking again.
 
Mine is at half too, the first few rides when I first had it new it came out the lid and splashed on the header.

My 401 was also the same, when the fluid got filled more than half it would splash out until low enough again.
 
Vatte said:
Are you thinking of the waterpump wheel?
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I was talking to an old ktm guy at the dealer and they said when the head gasket has a small leak over time its blown exhaust to the coolent will build up, which you can see easily by sticking the finger in the radiator where the cap is to see if carbon is on the metal of the cooler, when its cold of course.
 
It was the head gasket. Destroyed at the exhaust side (according my mechanic).
He changed it but I haven’t tried yet the bike.
 
Thanks for your replies!

My reservoir was not overfilled. It was always little over minimum then cold.
I sucked coolant from the over the top level of reservoir and filled it into the cooler. Then it was like it should be with cold engine, cooler full and reservoir at minimum.
I did also a warm up cycle in idle. The level in the reservoir was increasing but back to the starting level with cold engine. (y)

Next test will be a ride tomorrow. For that I filled the reservoir to the max level. I prefer some spill over against an engine with too less coolant.
 
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