If the 560SL is like the 560SEL, there are o-rings galore in that system... SIX on the compressor alone. Three on the low side hose to the compressor with that fuel cooler, one high to condenser, one condenser to dryer, four at the expansion valve, two dryer.

Chances are your 25 year old o-rings are causing your grief. An o-ring kit is about $10 from AC kits and about $5 for the o-ring lube (looks like snot). I suggest this before you go around and around. I had a cracked o-ring on my 560 at the compressor causing my leakage.

At that point I just opted to flush the entire system and start fresh, new dryer too. No telling what oil(s) had been added over the years. I added a good syn compressor oil that is 134A/R12 compatible and my choice of refrigerant. I would go with R12 unless you update the condenser as memory serves that the R107 has a fairly small system.

Hope it helps.

__________________
I'm not a doctor, but I'll have a look.

'85 300SD 245k
'87 300SDL 251k
'90 300SEL 326k

Six others from BMW, GM, and Ford.

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