You are correct, you have air in your caliper and that's not good.

You need to get a bleeder kit (cheap), and bleed the snot out of your lines. MB recommends replacing brake fluid every two years, so why not take this opportunity to do so?

I would start by using a very clean hose to siphon as much fluid as you can out of the brake fluid reservoir. No point in pushing it through the system in order to replace it. Get some nice new brake fluid (check the fluid specs).

Flush and bleed the system at the same time, and when you are done you've completed a maintenance item.

Don't wait to do it, do it now. You don't want that air in there (with its moisture) to cause any rust in your caliper.

Also, based on your questions, I'd say you need to read a Haynes manual on brake bleeding to get the general principles involved. You will also need to look up your model car and find where the bleeder screws are near the master cylinder.

If you're not sure that you can do this, get a qualified brake mechanic to do it. It's not an expensive job, and after all your life is on the line.


-tp