Re-fitting central heating radiator

Look for the spur marks on your backside as you are being taken for a ride.

The choice now is between DIY and Vaseline.

Cheers Andy. Of the two options DIY seems the most palatable!

Not necessary

You just have to be careful to open up the flow side isolation only, and bleed the bugger before opening up the return, or you will have a massive bleeding exercise..combi may need repressurising also. I am not a combi expert...so maybe I am wrong there.

You should be able to fit without problems. You will probably need to re-pressurise the CH circuit, but that is also trivial. You should have a filling loop and tap from the mains water, probably near the boiler.

It is worth adding corrosion inhibitor if you are not sure that you already have it. Conveniently it is available in gel form in cartridges for a mastic gun. Refit the radiator, tightening the unions. Squirt the contents of the inhibitor into the empty radiator and close the vent. The instructions on the cartridge usually talk about squirting it against the pressure of the system. Messy and you don't need to do it.

With the vent on the radiator closed, open the valves to admit water. Add more water through the filling loop until the pressure on the gauge reaches 1.5bar or so. Vent the radiator and repeat.

Run the system and the pump and vent remaining air. Adjust pressure so that it is around 1.5bar cold or 2bar hot.

That's it. The inhibitor will cost £20 or so and you will have a better outcome than John Wayne could achieve.