2001 silverado - My engine knocks for a few

You may have a bad intake manifold gasket, which is leaking the antifreeze in to your engine. Note" Antifreeze is corrosive to the engine bearings" and the knocking your getting from the engine may be worn connecting rod bearing and the pistons are knocking till it warms up and expands to take up the space the worn bearings created. Replace the faulty gasket, change the engine oil and filter as much as possible to till you address the leak and add Restor engine treatment and Lucas oil treatment for now. This may stop or slow the knocking for now, but your going to have to tear the bottom end down and replace the crankshaft and connecting rod bearings if the knock has not gone away. As the weather starts to get colder, your going to have to warm up the engine before you start to drive, getting hard on the engine while it's still cold may cause the bearing to slip and then your looking at a bigger and more expensive job. Good luck and keep me posted.