I'm sorry fellas, I know these get posted and it's damned near impossible to diagnose a sound from a video. Still, I'd appreciate it if you'd give it a listen and offer an opinion (even smart-alecky ones)

It only does it after the blazer has sit at least overnight. It does it worse in colder temps, naturally. Usually it quits within a few seconds, so it's very hard for me to diagnose. I've had my wife start it while I was under the hood with a listening stick and I'm about 80% sure it's coming from the passenger side of the upper part of the engine. It usually doesn't make the sound long enough for me to really get a good listen.

In this video, it makes the sound for almost a full minute. It will do that occasionally, but it's rare. It never makes the sound again once it stops. I've had the blazer about a year and a half and it's made the sound since I got it.

Blazer specs: 1997 Blazer, 4.3, 125,000 miles, serviced regularly.

The video: http://tinypic.com/player.php?v=2w6rrf9&s=7


Thanks!

 

hard to tell in the video, if you take another one, have the hood open and the camera near the engine compartment.

but from what you said if its coming from under the valve cover it could be a loose rocker arm, bad lifter.

what kind of noise is it?

 

Isn't that the check engine light that's on? What codes does it have? Yeah get under the hood when it starts & take a vid. Also you may want to invest ($5) in a mechanics stethoscope with the ear plugs to pin point the area.

 

The check engine light is because the cat is gutted and I need to buy one of those spacers for the o2 sensor to keep the light from coming on. Yeah, I need to buy a stethoscope. I live an hour away from the nearest place to get one, so I'll have to wait until I need to go over there.

 

Very commonly when engines get cold the pistons shrink and expand at a different rate then the engine block. I am 95% sure what you are hearing is called piston slap. My truck does it, it's not exactely great for the truck but it can't realy be helped. So what that noise is, is the piston ratteling against the side of the bore while they are heating up, and expanding. They heat up very quickly given what environment they operate in. Now if it were to do this when speading up or slowing down after it's warmed up(all the time), that would be compression ring noise and signals a rebuild in the future.

 

I appreciate the opinions. Thor, I've suspected piston slap. I guess I'll have to pick up a stethoscope to be sure. Even if I pinpoint it, there's not much I can do about it.