I had this identical issue in the last month - new freewheel, admittedly it was only £10 - but within a week it was creaking & making all sorts of noises. I thought my spokes had snapped at first. LBS took it apart and it had come from the factory with barely any grease - it was also surprising how small the bearings were - in other words the freewheel was cheap & nasty - a fairly well known brand as well. They filled it with grease and yes, there was an improvement once the grease had worked itself in but after seeing the cheapness I decided to change it anyway. I've since splashed out on a Shimano freewheel - much lighter and the quality is excellent - and it makes a very reassuring clicking noise.
Load the one you've got as had been said above, it should be resolved with some additional grease / oil.
Rick Powell 753 Track / Ribble Gran Fondo / Colnago Asso / 1975 Harry Quinn TT / 1990 Concorde Prelude / Vitus 992 / Keith Coppell Lo-Pro / 1986 KAS Vitus 979 / 1995 Mercian Strada Speciale / 2011 Raleigh GAC Militis 3 ex Graham Briggs / 1995 Ribble 7005 / 1986 Alan Super Record / 1985 MK1 Vitus 979 /
On the bench: Sirius 853 TT / Sun Solo Chrome / Ciocc Designer 84 / Giant TCR0 Pro Compact / Ribble 653 Tourer / Daccordi Lo-Pro / Look KG96 / Bottecchia Equipe / Look KG231 Credit Agricole / Contini Grand Prix / Aende Lo-Pro / TVT / Langdale 653 Pursuit /