2002 W208 Slow Trunk Unlock (Vacuum?)
 

When I unlock the doors using the remote on my 2002 CLK430 the trunk takes about 20 - 30 seconds longer then the doors and then finally unlocks. I disasembled the lock itself and its greased well with white grease and moves freely, is this a vacuum problem or maybe a cracked vacuum cable? The car has almost 45K on it and its in very new condition.

Did you check the vacumm line for leaks?

I have traced the problem to where I believe it is the device that locks the fuel door. It seems like it may need lubricated. If I lock/unlock 3 or 4 times the trunk and fuel door start to work ok. If it sits again for 30 minutes in the garage (about 40 degrees) it is then slow to release again.

Does it sound like a vacuum or lubricate issue?

Could that small black plastic piston on the back of the trunk lock have a cracked housing ?