I've drained the coolant out of my bike and found that my expansion tank is coated with dark deposits, making the level hard to read, so I removed it and filled with a mild detergent and boiling water. After leaving overnight I mananged to clean it out with a bottle brush. What I'm thinking now is that the water ways in the engine and radiator are also coated. Has anyone any experience with flushing out the system ?
The deposits could be from a previous water pump failure allowing oil into the coolant, usually leaves a grey deposit. Black bits are from coolant hoses breaking down. Backflush if you can, but be careful that you don't get any particles in the pump it can play hell with seals. The coolant passages should be fine. Remember to refill with de ionised water, this reduces the formation of limescale.
