tkamiya,thanks for your response. the old benz goes to 3 bars and then drops off to about .5 bars. When I give it some gas it never goes above 1-1.5 bars and it begins to knock. This all happens within 3-5 minutes. I described this to a dealer awhile ago and he said oil was bypassing some internal bearings.?? though others said it could be the oil pump or something else.
Thanks for your help