97 SL320 how dare you interject math into my dummy thread hahah.

Your right....I just went out to the garage and Ill be darned.....schrader valve. Leaned something today, thanks. So school me this, #1 cylinder can be verified TDC with valves closed by looking though the oil cap. How do you determine valve position on the other cylinders? Perform test with the valve cover off?

Bright side of the story, no more leak. Well there was one coming from the heater control valve which I knew was bad and a new one will be here early next week. I used a piece of double ended barbed nylon splice tubing to test the pressure. Took it up to 100c to test the thermostat / fan etc. No leaks coming out of the overflow tube.