Yes, if you are describing it correctly it is a pressure relief valve. No,,you shouldn't cause any major damage just by over pressuring it.That is what it is for. There are many things that can cause a system to over pressurize,and if it weren't for the relief valve,,you would blow o-rings and seals,,to say the least. One thing I would mention though,,,if you see alot of oil residue,I would think of adding a couple of ounces to the system.