Intermittent Knock

I have a 2010 with 195k miles it’s the 5.7 flex fuel. It has a knock in the very front of the drivers side head that doesn’t start till after the vehicle has warmed up enough for the thermostat to open and only knocks for approximately one minute then stops and doesn’t return. When it is knocking it comes and goes and seems to happen when something is cycling. Any help would be greatly appreciated. I have a video taken on my iPhone but it won’t let me upload it.

 

Did you ever get this noise figured out? My 2012 is doing the EXACT same thing. Seems like it's coming from the timing chain tensioner but when I pulled the driver valve cover it was still very tight and had no noticeable wear. I cant explain why it comes and goes as though something is cycling on and off. Reminds my of a failing ac compressor, but inside the motor.

 

I can’t listen to the video right now but is it possible that the valve lash needs to be adjusted.

 

Your timing chain tensioners are failing... I had the exact same noise on mine and narrowed it down to that. After it warms up best I can guess is that it is able to hold the tension. Mine started only during the winter and on a cold start then got to where it was a cold start any time of the year. I let toyota fix it, ran about $3000 out of my pocket but it’s cheaper than buying a new truck.