CH header steaming after new radiator fitted?

[carling_black_label]

Summary: I fitted a new radiator in a 15 y/o Y plan system now steam comes from header tank when CH called.

The method:
1st i drained system to nearly empty.
i fitted new rad.
i bleed lower rads
i bleed upper rads
i bleed pipes in loft
for some reason i put 3 way switch into manual (?)
i switched heating on
warmed up nice
hot water too
i put 3 way switch to auto
worked fine for a day????
noises in loft steaming etc from header tank
pump ran for a while
now bottom rads cold but still dont need bleeding
upper rads hot - bleed one or two again
still sauna in loft.
i turned down boiler a bit.

Any ideas?

Looking at forums my guesses:

blockage in system - sludge?

What setting for 3 way switch / valve (man or auto)?

Conclusion:
Confusion!

 

[doitall]

Where's the steam coming from, over the vent pipe or up the feed and expansion.

The valve should be the manual position when filling.

 

[kirkgas]

check the pump is free from air and turning, by removing middle screw and manually turning spindle with flat blade screwdriver

 

[twgas]

i would think a blockage in or near the cold feed/open vent connectios, thats if its plumbed in right in the first place.

 

[carling_black_label]

the steam was from the 'overflow' pipe, the one that just points in to the header tank,

went around the rads again, let some more air out a couple of them and it appears to be working ok. for now.

im certain pump is working fine, lower rads nice n warm,

is there a bleed valve on the pump? looks like a standard grundofus.

if i take out the center screw on pump, what am i looking for? free spin or resistance?

thanks for your replies.

 

[carling_black_label]

Ok so after all the f**kin about, every other day or so i need to bleed system?

Why am i getting build up of air in upstairs rads?

I put anti[-corrosion stuff in, i can hear water running through rads every now and again, it goes when i bleed?

is there a set way im missing to bleed, is it build up of gas in system?

any suggestions welcome.