I have a 88 560SEL. I converted to 134 about two weeks ago. The conversion was done by a guy that knows his stuff I believe. He put in the Ester oil to make sure the different oils within the system mix decently. Now, though, the compressor is making a "grinding" noise that it never did before when it still had r12. It didn't do it when he converted it but I think it has gradually gotten louder and louder since then. It starts as soon as I push the a/c button and stops as soon as the button is turned off. It still blows really cold but the sound worries me. I haven't talked to the guy that converted it yet. Thanks.