Lately I have had a tick from the engine, and I'm pretty sure it's an exhaust issue. I know some of the exhaust manifold bolts have come loose in the past. I want to replace them. I didn't find anything on gaskets for them so I assume there are none. As for the bolts, should I use extra precaution as they are old and rusted especially in aluminum? This tick is driving me insane. Also if there is a couple small holes in the exhaust pipe back between the center and rear muffler will that cause a tick while driving?

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1984 300SD Orient Red/ Palomino
1989 560SEC
2016 Mazda 6 6 speed manual
1995 Ford F-150 reg cab 4.9 5speed manual