steam radiator replacement

difficult?

You would need to put a reducer in the supply (or if 2 pipe either supply or return), and then have an accumulator pump with an accurate gauge, or a compressor with a regulator on it that will measure in ounces. Then couple the source of air to the reducer (if 2 pipe, seal the other end) slowly apply the air, and spray with a leak detector solution, ie. dish soap diluted with a good bit of water. Where it bubbles it is leaking. I would check for a minimum of 2 psi, but since the safety check valve of the boiler is set to blow at 15 psi, a pro might want to see it tested up to that range.