Hot rads upstairs cold down

[Rogerf]

Customer has an ideal logic 35 with heating working upstairs and no heating downstairs, have tried shutting all rads upstairs but rads downstairs still cold, I did find some stuck trvs but still no difference once released, I’m thinking system is sludges up.
any other opinions

 

[Gasmk1]

pump not working properly

 

[snowhead]

As above or maybe separate zone valves upstairs and downstairs.

 

[Rogerf]

If it is the pump i would of thought rads would still get some heat downstairs as all on drops from above, no zone valves on system

 

[SimonG]

Either as said pump or downstairs on a second zone.
[automerge]1589384552[/automerge]
Gravity hot wont gravitate down hill.

 

[SJB060685]

I'd be checking the pump first mate