The radiators heat up to half - It only heats the top of the radiators

The radiators are most likely starved of flow, not air: if the supply is hot and the return stays cold, the water is not passing through the whole radiator, and the cause is usually a silted/clogged valve, blocked branch pipe, or badly balanced piping that makes the pump take the easiest circulation path instead [#11842624] [#11850860] Check that the supply and return valves are fully open, and if there is a thermostatic valve, unscrew the head and inspect the presetting/insert under it; one user fixed a similar half-heating radiator by moving that adjustment, and another reported better heating after replacing the supply valve so more water could pass [#11842100] [#11843156] [#11903240] Try throttling or closing the other radiators to see whether the weak one starts heating better, because the installation may be badly balanced and the pump may be sending water through the shortest loop instead of through both radiators [#11846222] [#11850723] [#11850860] If the pipe run goes up and then down, or has sharp bends and small cross-sections, that can also restrict circulation; photos or a diagram and pipe diameters would help confirm it [#11842506] [#11842336] [#11849017]