Comments by "Rick2010100" (@Rick2010100) on "HumbleMechanic" channel.

  1. The oil is so black that it is probably completely worn out. With oil like this, the valve caps cannot last long. Individual ones are usually extremely worn when a piece of metal has become stuck there. The shaft presses it into the valve cover and then the mutual grinding begins. The piece of metal is eventually gone, but the unevenness continues to grind because the surface is specially hardened and the hardened layer is then gone.
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