Please help - cold rads downstairs!!!

Just removed one of the radiator downstairs for a quick flush in the garden as it took a long time to get luke warm. Now all the downstairs radiators are cold. The pipes leading to all the downstairs radiators are cold.

Upstairs rads are working fine.

Since then, the boiler in the kitchen is also hisses when the heating comes on.

I've been reading up some of the suggestions posted and think i have air lock in the pipe. I tried closing off all the valve uptairs but has not worked so far. Any other suggestions on how i might resolve this problem?

Thank you in advance!

Bleed at every point you can, including the one by the pump, assuming you have one.

Thanks for the reply. I've bled very rad, but still no use.

How would i know where the pump is in the house? What does it look like?

Thank you in advance!