yeah but it forces it all in to the resivior until it can't hold any more

 

then mabe you have something clogging your system Id say. the water pump is trying to run wather through the system but if youre pathways into the motor are clogged the waterpump may be working faster than the water can flow and would therefore force it into the overflow container. ?? just a guess ??

 

ok i'll mention that next time i take it somewhere, or if i feel like ripping it apart myself