heater not working with new rad

hi, i have a disco 300tdi i have just replaced the rad because the old one was leaking and now the heaters blowing cold. it worked before the new rad. also i lost the expansion bottle cap so have put a rr one on which doesnt fit to well could this be the prob?

wrong cap wont help , Id say you still got air in the system , did you bleed the air out at rad and thermostat housing and take your time , it's not a 2 minite job to do properly .

no i didnt know you need to, how do you do that?
i filled up with water took for a drive then filled up again and it hasnt gone down since

many different method's , but mine is , engine off, fill rad at the plug use the correct size socket , brass plug will take some stick plastic one wont . when full replace and then fill at therm housing . when full , remove small pipe on left of housing , held on by a jubilee clip fill expansion tank until water leaves end of pipe , put you finger on the outlet the pipe fit's to or you will loose water . refit pipe top up tank run engine and check for leaks . be careful of the fan , open heater to hot as you start engine . you may need to get correct tank cap to ensure you don't loose pressure when engine is building up temp
this should help as i stated different people different method's , they should all add up to the same thing , cool running and heaters

be careful with those ****ty plastic bungs - they tend to break. Replace with brass ones.

and use the correct coolant bottle cap, or it could well overheat.

The Mad Hat Man said:

be careful with those ****ty plastic bungs - they tend to break. Replace with brass ones.

and use the correct coolant bottle cap, or it could well overheat.

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do i detect a bit of spam to follow shortly

not necessarily - but if yu are offering?

thanks got it sorted now was a bit of a mission to bleed it with the wrong size cap but got there in the end, the caps not permanent its just until i get a the right one delivered