cooling system expansion tank

[mickeyflyn]

just solved my temp light flashing problem light was flashing intermittent ,reason needed topping up in main tank at rear.my expansion tank was nearly full though at cold.
i have now drained the expansion tank to the max mark.

brought van up to temp until fan kicked in ( first time i`ve ever heard the fan ) bled a little air from rad topped up again and all seems fine.

any input would be good ?

[Wychall]

Not an expert on these things but I am sure that I have seen previous threads which suggest that the problem may be the "dalek" pressure cap on the main tank. Is it failing to suck water back in from the expansion tank?

[mickeyflyn]

sounds plausible but i don`t have a cap like that. i have a normal steel flat cap .

mickey