Hello, so I have a 2000 CLK320 with 155k Mileage on it it’s been taken care of really good previous owner has had it for 11 years took good care of it. I step on it every now and then but not always. I have a muffler delete. SO THE REAL ISSUE, Recently there’s a ticking noise coming from the passenger side of the engine, the day it was loud turns out my oil was a little low I had to add 1qt of oil. I read on the forums that it may be from the purge valve but I touched it today it was beating same time the ticking noise came from the passenger side of the engine then the beating went away but the ticking is still there. Is it something serious? What can it be? Is it expensive to fix ? I’m scared that my engines messed up or what the issue is. Please help in any way possible thanks