We'd recommend first driving your Mercedes 560SL for a few days and conducting a quick inspection at home similar to the smog stations smoke snap test. Ask someone to stand 10 feet from your Mercedes's tailpipe. While in PARK press the accelerator quick to achieve 2000-3000 RPM and release. White (or Black) smoke should not emit from the tailpipe.
Visible white smoke typically indicates water and/or oil seepage into the combustion chambers. Water has an opportunity to enter the combustion chambers via a damaged head gasket, at the junction of an engine's valve head and engine block. This will typically cause overheating and white smoke in the exhaust coming out of your Mercedes tailpipe.
If the white smoke has a blue tint to it there might be a possibility that your Mercedes is experiencing an oil burning problem rather than water. The best test for this is simple measuring the amount of oil loss over a period of time. Anything greater then half a quart of oil loss during a month is too much and may indicate a leak (internal or external). If this is the case, you want to check your Mercedes's valve seals and piston rings, both of which can be tested via a compression test. The administrator of the compression and vacuum test must be proficient in reading these test results.
Excessive white smoke is normally emitted typically on cold days, and when the engine is not properly warmed up. White smoke during startup or during cold weather is just steam, and will not cause a smog test failure.
