Radiator hot at the top cold at the bottom

[swole_badger]

All radiators in the house are roasting hot both top and bottom apart from this one down stairs in the living room. It is only hot at the top and mild warm at the bottom.

I have bled it before but it remains the same.

Any ideas?

 

[Wayners]

Rust and sludge built up at the bottom maybe.
Take radiator off and wash out...

I took radiator off once. I could not get water out of it. While I had the radiator outside a black sausage of sludge oozed out then blackwater. Washed it through and put back on

 

[CountryFan]

Looking at the trv, I’d be exploring the pin operation, they can stick.