Just an update as I forgot to make one last month.
New idler fitted, bloody noise still there.
I am very sure it is coming from the AC compressor.
When I stripped it all down (to do more than the belt etc) I took the compressor completely off so I could access the rocker gaskets etc.
When I took it off it gave me the opportunity to change the O rings too, but as I turned it sideways some fluid leaked out of the holes, a very small amount - maybe 2 - 3 table spoons or so.
Could this be some compressor oil?
Checking Rave it uses 0.32 US pint of Sanden SP10.
I could "put" some back in via the holes it came from, but there also seems to be an oil plug.....
Could anybody advise on this please?
Found this for a Sanden compressor:
Compressor lubrication occurs as the oil which circulates with the refrigerant passes
through the compressor crankcase during operation. The Sanden SD series (not sure if LR uses this) compressor achieves optimal durability and cooling performance when oil circulates through the system at a ratio of 3.3% to 8% oil to refrigerant.
As far as i am aware lube for the drive (eccentric cam) is separate from the lube in the pressure system. That is the usual way aircon compressors are constructed. There are two chambers drive chamber and pressure chamber.