Noisy Frig Compressor

[Albro359]

I have an engine driven frig compressor, SANDEN 501.
Recently the system had a leak and emptyed all the gas ...found it, now fixed. System was regassed by a local frig mechanic and now after about an hours running, there's a terrible graunching noise coming from the compressor imntermittently.
The belts are OK, the mounts are good..I know its the compressor, 'cos if I relase the clutch the noise stops.

It just occurred to me that maybe the system has too much gas in it (overcharged) and after an hour liquid refrigerant is getting into the compressor - it can't compress a liquid - and therefore the noise.

Any frig experts out there with some ideas ?

If this is the problem, can I just release some gas out of the Shraeder valves to cure it ??

Cheers
Alan