I was going to remove the anti-freeze expansion tank on my 190E yesterday just to give it a really thorough cleaning. After being filled with coolant for the past 17 years it has gotten kind of slimy inside and I can't see the level of the coolant without taking off the cap and looking inside.

I removed the one nut and the plastic fastener at the end of the tank, but when I tried to remove it I found that the bottom of the tank is attached the the inside of the fender. I gave it a firm pull but I was afraid of breaking something seeing as how the plastic tank is 17 years old. Is there a trick to removing this tank? I looked up the tank in Fastlane to get a better look at the bottom and it looks like it just has a plastic knob that pops into the fender. My tank also has a rubber grommet around the knob that connects to the fender. Any advice would be appreciated. Thanks!