I am wanting to check the transmission fluid in my Benz. I found a dipstick at the back of the engine but the cap says MB Shop ONLY. It is a round cap with a retangle tab on it. How do I open this and is this what I want to do to check the fluid level and even suck out the fluid from??

 

break the tab and push down the lock. don't lose it for you need to put back the lock after checking

 

Thats not a dipstick. Thats only a dipstick tube cover.