Overflowing coolant


This has me stumped. I cant seem to keep coolant in my radiator without losing it outthe overflow. I have just replaced the seals in the waterpump (all other parts were good) hoping it would fix the problem but hasnt. Im hoping that its simply just the incorrect radiator cap and just allowing coolant to pass before it gets to pressure. Bike isnt overheating as it happens just after it gets to temp. I have noticed the overflow tank is filling but not sending fluid back to the radiator.

Has a new head gasket in and almost all parts are in great cond as its done less than 1000kms.

Also managed to get a massive oil leak from where the oil line bolts to the engine after taking it apart for the waterpump. Im hoping thats just the o ring.


You say it isn't overheating, but you say coolant is coming out the overflow.....


Have you tried a new cap? Go to 1.6 instead of 1.1,

Going to a 1.6 cap isn't solving the problem you have

A 1.1 cap is fine, if there is no other problem.

Golden rule of problem solving is don't change something to fix the symptoms of a different problem - fix the original problem!


Assuming you haven't got an airlock in your system, try a new 1.1 cap

If that fails, head gasket is suspect as combustion gases are getting in to the coolant system and blowing past the rad cap as the pressure is too high

Another thought


your water pump repair went wrong and the pump isn't flowing any water, so it is locally boiling the coolant around the cylinder causing excess pressure


If it was fine before you repaired the water pump, then I'd start there as its the only thing thats changes

You say you put a new head gasket in it. Did you test the cylinder head for warpage or cracks? Is the cylinder warped? Can you smell combustion in the coolent?

Or better yet, coolant in the combustion (exhaust) - along with steam if that's the case.

Pressure test the cooling system


a few recent threads with similar problems ended up being head gasket related

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