I'd like to thank everyone for all their suggestions when I couldn't find a good Mercedes machanic in Toronto.
I found one and he is awesome. Turns out the back and hardest glow plug to get to was gone and another needed cleaning for contact. He switched me to a synthetic oil and found that the energy drain was caused by a fuse that probably been added for a cell phone or a radar detector.
Once again thank you Judy
Good to hear it worked out for you. That first mechanic was totally incompetent. Most of us here who aren't even professional mechanics, but work on our own cars, could have found those things very easily. The hardest thing there was probably the battery drain. Even that, unless it's intermittent, can quickly be found to exist by just connecting an ammeter to the battery cable. Finding the actual location of the problem causing it, can be more difficult.. But clearly the first guy didn't even know how to tackle any of this.
We appreciate your letting us know what "the problem" actually was. Appears you have found an able mechanic who will now take good care of your 300SD.
MotorsForum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.