Couling system problem

[sasasvara]

I have just bought GPz 400 (1990 Ninja) that has not bean used for 4-5 months and I am lousing coulant from overflow pipe( the one that comes underneath the bike near back tire. I have remouved thermostat thinking that that is the problem but I am still lousing coulant. This hapens when I stop after bike is driven for 15-20min and the coulant that comes out is not hot.
Any ideas?
Someone told me to bleed the couling system ( how to doo that? I have tried to do that trough bleed nipple on water pump but I am not sure for how long shuld I do this or how !? ) Could it be that there is a blockage in the system ( how can i unblock it?)

HELP

[southjersey636]

Pull off the radiator cap while she is cold, then undo the little bolt on the water pump and let her flush out, then if you want, take a hose and run water through where the radiator cap is until you see the water turn clear coming out near the water pump.

Afer you do this, if you can remove the overflow tank and clean that out cause its probally got gunk in it.

Now your all set to fill her up, start adding coolant to the radiator until you see it come up to full and add up to the line on the overflow tank. Go out take her for a ride and when you come back, let it sit for awhile then remove the cap and top off the radiator if it needs any more coolant.

Let us know if this fixes the problem. Also is the gauge showing warm?

The overflow tank is ment to do what it says, to purge out some excessive system pressure and this sometimes will show by seeing drops of coolant on the ground where the hose is.

[sasasvara]

I have try that all but taking owerflow botle out ( I clean it with lots of water ) but I still have the same problem. In the begining water is not hot but second or third time when comes out it is. Sometimes steam come out as well and then I top up water in the radiator. Gauge is newer showing more than half between C and H but that can be because there is no water in the radiator. Could it be blockage, faulti owerflow botle or is my bike ower heating to much from other reasons. By the way this hapens only in town rides and newer on open roads.