Rattling Noise.

[jsoden]

Hey all. Quick question. When I fire up my truck (00 Sierra z-71 5.3L) first thing, I have this weird rattling noise from under the hood. (it's not the piston slap/dieseling sound). It goes away when I rev the engine, but when the idle drops down after the rev, you hear it more. When the truck warms up, it seems to go away. I replaced my AC belt and tensioner because it sounded like it was lower and I noticed it bouncing more than I thought it should. The bounce was made better, but I still have that sound. I was thinking maybe the pulley on the water pump?? I will replace my tensioner and serpentine next to be sure, but just wanted to see if anyone out there has had a similar problem. It's not a loud noise, or a clanging noise. I can't really describe it, but more like a vibrating kind of noise. Engine runs at constant temp with no fluxuation on the needle, so I didn't think the water pump was going bad at all. It sounded to me like the sound a pulley would make when the bearings in it start to go. Any ideas before I spend a lot of money and time to yank out the pump? I'm not one who likes replacing things that aren't broken. Thanks!

[drknow90rs]

Idler pulley? About the only thing I can think of...

[jblakeney]

Valve train?........... Lifters tend to make noise if they loose prime till they are primed back up. My 99 5.3 has done it since I have had it....

 

Jbo

[Wires]

Hey all. Quick question. When I fire up my truck (00 Sierra z-71 5.3L) first thing, I have this weird rattling noise from under the hood. (it's not the piston slap/dieseling sound). It goes away when I rev the engine, but when the idle drops down after the rev, you hear it more. When the truck warms up, it seems to go away. I replaced my AC belt and tensioner because it sounded like it was lower and I noticed it bouncing more than I thought it should. The bounce was made better, but I still have that sound. I was thinking maybe the pulley on the water pump?? I will replace my tensioner and serpentine next to be sure, but just wanted to see if anyone out there has had a similar problem. It's not a loud noise, or a clanging noise. I can't really describe it, but more like a vibrating kind of noise. Engine runs at constant temp with no fluxuation on the needle, so I didn't think the water pump was going bad at all. It sounded to me like the sound a pulley would make when the bearings in it start to go. Any ideas before I spend a lot of money and time to yank out the pump? I'm not one who likes replacing things that aren't broken. Thanks!

 

 

My guess is the core in one/both cats right off the manifolds let loose. My '00 had that the ones under the cab. It had a rattle when idling, slight increase in throttle/load, and it went away.

[grogman45459]

Hey all. Quick question. When I fire up my truck (00 Sierra z-71 5.3L) first thing, I have this weird rattling noise from under the hood. (it's not the piston slap/dieseling sound). It goes away when I rev the engine, but when the idle drops down after the rev, you hear it more. When the truck warms up, it seems to go away. I replaced my AC belt and tensioner because it sounded like it was lower and I noticed it bouncing more than I thought it should. The bounce was made better, but I still have that sound. I was thinking maybe the pulley on the water pump?? I will replace my tensioner and serpentine next to be sure, but just wanted to see if anyone out there has had a similar problem. It's not a loud noise, or a clanging noise. I can't really describe it, but more like a vibrating kind of noise. Engine runs at constant temp with no fluxuation on the needle, so I didn't think the water pump was going bad at all. It sounded to me like the sound a pulley would make when the bearings in it start to go. Any ideas before I spend a lot of money and time to yank out the pump? I'm not one who likes replacing things that aren't broken. Thanks!

Maybe baffle(s) that have broke loose inside the muffler?