My CBR900rr has leaked coolant from the reservoir

[jonathan26]

My cbr900 fireblade 1999 has leaked coolant from the pipe connected to the top of the coolant reservoir. This pipe has an open end which leads to the bottom of the fairing. I had been out on the bike, no apparent problems with over heating. After parking up the bike, I noticed coolant coming out of this pipe till the reservoir emptied. when the bike had cooled I opened the radiator cap to find the coolant 2-3 cm below the overflow pipe.

What could cause the reservoir to do this?

Any ideas appreciated.
Jonathan

[Pete.]

The most common cause is over-filling the expansion bottle. It should be no higher than the line when stone cold.

Might be it just needs a coolant change.

Other than that you might have a failing pressure cap. If the system doesn't get up to pressure it'll boil and the excess will expand into the expansion bottle - the lower the pressure the more expansion.

Similarly, if the bottle level has been allowed to get too low it might have drawn air into the system when cooling, instead of drawing the coolant back in.
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a.k.a 'Geri'

132.9mph off and walked away. Gear is good, gear is good, gear is very very good

[jonathan26]

Ok thanks for that, since the coolant has recently been changed, look like it might be the filler cap.

[Pete.]

[andys675]

the "reservoir" is a catchment tank for coolant expansion, once sorted I would run it at the minimum mark to help avoid overflowing in future
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Some people feel the rain, others just get wet.