Another water mystery.

Hi i have a 2006 990 with 19k miles on it. I losing a quarter of a mug of fluid on a 30 mile ride out of the expansion tank. i noticed the tank was empty, topped it up and marked it then went out on a ride. when i parked up the water level was the same but as it cooled the level dropped by roughly 2 cm. The level was in between min and max.

Before the ride i cleaned the radiator valve and there was a little crusty build up on the seals. i have checked the oil and it isnt creamy, its nice and clean. the radiator is full to the top and i am being very picky but there is the occasional spot on the surface but definitely no custard creamy stuff there. No knocks bangs or rattles. goes like hell. engine sounds sweet as anything. not using oil. no funky smells our obvious leaks. The bike came with loads of recipts and a full service history and i cant see any major work done to it, i also cant see any evidence of the waterpump seals being done.

Have just read the newish post on this and seems like a similar problem but please please please dont say cracked head.

Any ideas what to attempt first?

Sounds to me like there is air in the cooling system and that's why its using water from the over flow tank.
When you go for a ride is the engine temp hotter than normal?
It should be around 6 to 7 bars on the temp gauge.
You might just need to burp the radiator.
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4 bars. occasionally 5 in traffic. plenty of heat comes off in traffic but not enough to trigger any warning lights.

does the front wheel have to be 50cm off the ground to burp the bike? will try the cheap things first. new rad cap is in the post.

If you have a steepish drive way that will work also plus when you do it take rad cap off engine not running and give the lower rad hose about 10 to 15 squeezes to push air out of the system.
Don't forget to loosen the bleed screw

If it gets worse, check the oil again. I had a 950 and the water pump shaft seal is a very common failure. Started slow at first, then eventually it was dumping a lot of oil into the coolant.

Burped the tank and while i was at it i split the airbox to see if there was anything in there and lo and behold we have cheese!!!!


if i am not mistaken this is water pump knackerage right? the cheese came from that breather pipe.

Yes you need the water pump repair kit, no biggie to do yourself.