Knock Sound

[flintlock]

Hey guys, I have a 1997 k1500 cheyenne 4.3 nv3500, I got the truck 2 years ago this month. When I got the truck it had 196,000 miles on maybe original motor. I noticed from the bat a light knock heard moreso on the passenger side. Changed the oil with 10w40 and lucas additive. Noise mostly goes away until the oil breaks down and gets thin. Ive driven the truck over 15,000 miles and do not baby it but Im also not hard on it at all. I'm assuming this is a rod bearing knock. It goes away with increased rpms. It isnt a ****, ****, **** noise more of a **** ****....****...**** **** ****...**** ****...**** noise. Upon startup when warm, it makes a dunkah, dunkah, dunk noise same sound and pitch. This noise is only heard when the oil is hot. The truck holds good oil pressure, 60 at start up 30+ crusing down the road at operating temperatures and 20 at warm idle. What do yall think? I'm starting to believe it is not a bearing knock. I've accelerated over 3000 rpms many times and I have red lined it in neutral once or twice for giggles and my mechanic squalled tires once. I would assume it would have spun a bearing and locked up by now, or are Chevys this tough? Lol

 

[flintlock]

Edit* the noise has not gotten any louder not a single bit it is now at 211,***.

 

[Fuzzy]

If you could get a video of this sound that would help a lot. That said it sounds like a Rod Bearing, I will tell you from my own truck that I drive very hard, (Also a 97 K1500 4.3/NV3500) with the stock engine (Running 5W-30 Full Synthetic 6k Changes) and 279,000 miles on it now, your oil pressure is a bit low. At cold start I'm at 50, Warm Idle 40 and 60+ on the highway. Though your truck is above GM's minimum of 5psi, that engine with healthy bearings should make much more than that.

 

[flintlock]

It sounds exactly like a rod bearing knock Fuzzy, and thats really neat you have the same truck setup. I'll see about a video sometime soon. We have a perfectly maintained 07 yukon nnbs 5.3 that doesnt hold any better pressure with the same amount of miles (200,000+). I am simply curious though how this truck has not blown up yet. Has anyone else had a vehicle knock for a long time?

 

[flintlock]

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[flintlock]

This is the video guys, this sound is most prevalent on the passenger side fender well, quietist when under the truck. I'm beginning to wonder now if it is related to the timing gear balancer or something in there. The timing chain sure makes fuss and it spark knocks like crazy. I guess it could be getting thin oil and create this knock sound. I hear the same spark knock sound when the truck is about to stall out or die. I appreciate the help folks, and please nobody tell me to rebuild the motor or replace right away, just want opinions and yes I know how to ground out the plugs, just don't feel like it yet. I have way to much on my plate and way to many vehicles to drive to worry about this hunting truck.

 

[cookseyb]

Piston Slap, 10-50 Mobil one, Hi Mileage oil will help.