2005 GMC Sierra 1500 ticking/knocking noise?

[Flying_Lavey]

So his current shop has not been able to hear or replicate the ticking/knocking noise but...he found that one or two exhaust manifold bolts are broken off. My son didn't remember exactly if the mechanic said one or two bolts. That might be something that is an issue on a cold start, sometimes and goes away as the engines warms? It doesn't happen on every single cold start but most of them. It sometimes happens a couple of minutes after the cold start then goes away 5-10 minutes later.

These engines are also notorious for popping exhaust manifold bolt heads off at the corners. The manifold will warp afterwards and usually need to be replaced or machined or else it will happen again. Usually it doesnt cause much of an issue when they are broken though.