coolant expansion tank

[remember1t]

I am finding rusty water leaking from the cap of the expansion tank.
There is no rubber washer on the cap. Could this be the reason why - or should there not be a washer and my symptoms are indicating something more sinister ?
Any advice welcomed.
Thanks
Geoff

[onzarob]

But a new cap,flush the system and see how it goes, its an old car there is going to be a lttle bit of crud, coolant should be changed every 2 years

[remember1t]

thanks, I'll try that rob - if a new cap is available. (is there a separate rubber washer - or is it just a plastic (nylon ?) cap
Regards and thanks for replying so quickly;
Geoff

[onzarob]

the cap should have a rubber sealing ring