Radiators cold at the top, also low pressure

[JingleBellaTheGymnast]

We have GCH. Radiators downstairs and one upstairs are fine. The other two upstairs are cooler at the top than the bottom. We bled one, and air came out, but although it's improved it isn't totally fixed.

We can't turn the key in the other, even with WD40 it won't budge.

The pressure on the gas boiler is right at the bottom, in the red zone.

Have looked at the manual, and there is nothing mentioned about how to regulate the pressure. Any ideas? Button options are Reset, Eco, and one with a spanner symbol. Do we need to call someone out?

We can live with the heat issue, but are we in danger of damaging the boiler?

Try and get a bigger radiator-bleeding key. You might break the pin off though. If the screw is set in a hexagonal or square socket, the socket is part of a plug that can be unscrewed with a Radiator Wrench and a new plug and bleeding screw fitted in. More modern plugs can be taken off with an ordinary spanner. It is absolutely essential to tightly close the valves at both ends of the rad first, or water will squirt out. As your pressure is currently low, it's a good time to do it. If you are not fond of plumbing, find someone who is.

Repressurising the system is done with a filling loop. It should be described in the manual. Usually a metal-braided flexible hose with a valve at each end. It is absolutely essential to close the filling loop at both ends after topping up, and preferably disconnect it at one end to prevent leakage which will cause excess pressure. Do not overfill it.

If there is any sign of dripping or water staining on the outside wall behind the boiler, the pressure relief valve has been dripping, and will probably need to be replaced or dismantled and cleaned. Once they have opened they often fail to reseal tightly.

Fen the sounds of the buttons you have a Worcester greenstar boiler. The system on this boiler is filled via a key which is slotted in from underneath. There is a handy how to video on YouTube. No link but search greenstar filling loop and it will come up! If you don't have a greenstar this will be meaningless however! If you do have a greenstar then please please please do not overfill the system. The pressure valve mentioned by pj is the most difficult part to remove on this boiler and will cost a fair bit to replace.

Success! It is indeed a Worcester boiler, found the filling loop, turned the tap and the radiators are hot to the top!

Daft user manual, MN is the place for advice.

Yup, broke the spindle off the radiator key.