5.3 Knock/rattle

Vmax53 · November 23, 2015

Ok guys, I am at the end of my rope. I have a 2005 5.3 Silverado z71. Vin code B. I have developed a rattle/knock under the truck. The engine does not make one sound until it reaches around 180-190 degrees. I can crank it and sit by the ground and wait for it. It starts out subtle. tap....tap tap......tap tap ting tap.....tap tap tap tap tap tap. Very repetitive. Loudest at the bellhousing. Here are a list of things that I have investigated. First thing was i drained the oil. No metal on the plug but from what i could tell, looked like a little GOLD GLITTER in the old oil. Put fresh oil with a quart of trans fluid hoping it was a lifter issue. No change in noise after 2000 miles. Drained oil, went with a 10w30 oil, no change in noise. Oil pressure never below 40psi even in 100 degree louisiana weather. Beat with rubber mallet on CATS hoping to hear a rattle, no rattles what so ever. No exhaust leaks or broken manifold bolts. Unbolted the starter and checked all torque converter bolts. All were tight with OEM loctite installed. Went ahead and took the torque converter bolts loose, pushed the converter back, and cranked it up. Same noise, same time, same temp, everything was the exact same. Didnt change at all. Bolted everything back up and this is where i am. My next plan is to take the valve covers off sometime this week and spray down the bush rods to the lifters. Maybe one of the ports are clogged on the lifters. My fear is that it is a bearing of some sort. But TYPICALLY with bearing slack, it does it all the time correct? The noise goes away AS SOON as you push the gas pedal. Any increase in RPM the nose disappears then reappears after a few seconds of idling. Any help would be greatly appreciated guys. I have attached a video. Hope it works.

00Silverado4x4 · November 23, 2015

Hate to say it but the gold glitter sounds like you may have a bad bearing in the crankshaft area. Unless you're really handy, I'd get it to a shop and have them look over the engine internals on the lower end.

Vmax53 · November 24, 2015

Thanks for the reply. I am pretty handy when it comes to these engines. I tend to agree with you on the bearing issue. My only confusion is as to why it doesn't do it until it warms up. Maybe its all due to the viscosity decreasing that much that it increases the tolerances within that worn bearing. That is why i tried a thicker oil but didn't seem to have any affect on it. Ive even tried some oil stabilizer on my last oil change before i changed it. No difference.

00Silverado4x4 · November 24, 2015

If you have the ability I'd be pulling the oil pan and get a real good look at everything on the lower end for sure. Worst case that I can think of would be a loosing connecting rod and that could lead to full break down if not corrected.