rattle or slight knocking noise in engine

[bscoffey]

Now that i have the brakes fixed i'm gonna move on to the next problem. I have a noise in the engine area that i can only hear at or around 1500 rpms thru the 2000 rpm range. It sounds like a piston rattle but only at those rpms. When it gets above 2500 rpms it dosent rattle anymore and it dosent rattle at idle either,dosent rattle at start-up. i dont think this is doing any damage to the engine ,there is no metal in oil . just wondering if anyone has had this problem or has herd of this problem. I read somewhere the flywheel might be cracked or it might be the torque converter, i just dont know . I thought i might try to get some of these problems taken care of while everything is slow and i had some extra time.

[Gus_Mahn]

It's hard to say for sure without hearing it in person, but the 4.3 vortec is known for making balance shaft noise. My '97 does it a little. My brother's '99 makes a lot of noise. To me it sounds like main bearing noise. It's really never changed much over time on either of our vans and doesn't seem to be an issue in any way.

GM had a kit to fix the noise, but I believe it's been discontinued. I know one guy who disabled the balance shaft to stop his noise. The engine ran a little rougher at low rpm, but the noise stopped.

Here's a link
http://www.s-10crewcab.com/og1/modinfo/ ... eshaft.htm

[01safari]

I have the noise also. It sometimes is annoying, but as long as it is not causing any harm, I plan on leaving it alone unless I have to replace the front cover.

[bscoffey]

thanks gus im thinkn that the prob. if i get froggy i might remove mine. Sometimes i wonder about these engineers.i think they should have to work on what they design. i have a misfire problem now.

[Casey]

I suspect I have this same issue with my '95. I checked out the bottom end when I had the oil pan off, and everything checked out fine, but I can't seem to narrow down the specific location of the rattling as it sounds like it coming from inside the engine. It doesn't seem to be coming from one side more than the other, but my hunch was on the driver's side based on what I'm hearing in the driver's seat (which I know isn't always 100% reliable for diagnosing). I suspected a stretched timing chain or possibly a loose rocker arm, but the engine has only 95K on it, so that would be a bit early for a stretched timing chain IMO.

Is there a way to check the balance shaft for excessive play with the timing cover removed? The FSM simply tells you how to remove it and install a new balance shaft and the bearing at the rear of the block, not how to check for excessive wear.

Now I'm curious how much vibration the balance shaft dampens out...

[bscoffey]

im not sure if you van check the play in the timing chain area. I checked mine when i replaced the intake gaskets.It did have some play in it but i thought it wasent much. Apparently it was too much. There is a tsb on thr rear bearing on the bal shaft that would wear but not enough to warrant a replacement according to GM. Which GM uses the public for a test market. Anyway it hasent gotten much worse so im gonna drive it till it drops. If i have to tear it down i will rebuild it to tighter specs that what GM recomends. Your problem prob is the noise you r hearing .I think (this is just my opinon) that the engines built at one plant has more problems the the engines built at the other. The 4.3 is built at two different plants and my opinon is that one plants workers are lazier than the other plants. therefore the quality is lacking. I has a 95 model and ran the crap out of it from day one and it never gave me any trouble. It is a completely different story on this one. As soon as i fix one thing something else tears up. I just replaced a lazy TPS and the van runs great at WOT but now my gas milage is now in the single digets. Oh it did take care of the misfire problem i had at WOT.But now i have a miss at part throttle. I think if i could kill , skin & eat this thing i would .

[tedanderson]

Thanks! This is good to know. I've been considering buying a 99 (it belongs to someone who I house sit for) and I have been a bit reluctant to buy it because of that knocking sound.

[bscoffey]

yea if the bearing problem was addressed by GM along with a grocery list of othe things i wouldnt hesitate in buying the 99. But there are too many issues with these vans that GM WILL NOT deal with. If I buy another GM it wont be a lower line : s-10 , astro ,colorado etc. It will prob be a silverado , or GMC brand.Seems like they take a little more pride in those when they put them together.

[bscoffey]

yea if the bearing problem was addressed by GM along with a grocery list of othe things i wouldnt hesitate in buying the 99. But there are too many issues with these vans that GM WILL NOT deal with. If I buy another GM it wont be a lower line : s-10 , astro ,colorado etc. It will prob be a silverado , or GMC brand.Seems like they take a little more pride in those when they put them together.

[bscoffey]

yea if the bearing problem was addressed by GM along with a grocery list of othe things i wouldnt hesitate in buying the 99. But there are too many issues with these vans that GM WILL NOT deal with. If I buy another GM it wont be a lower line : s-10 , astro ,colorado etc. It will prob be a silverado , or GMC brand.Seems like they take a little more pride in those when they put them together.

[moneymaker]

That's pretty funny being the chevy, gmc, and caddy go down the same assembly line!

[bscoffey]

I didnt know the Silverado went down the same line as the Escalade? Are you sure about this? Didn't know the Astro went down the same line as the Serria. Are you absolutely sure about this? I didn't know the Camaro went down the same line as the CTS. Are you positive about this?

[Leeann_93]

Don't know about the rest, but the Astro was built in a plant that only built Astros.

[Jasen]

It used to be, when a German dropped a heater knob for an 911, he would just pick it up and put it in the Beetle that was next in line.

[Leeann_93]

Just found this looking for something else...

http://www.enginebuildermag.com/Article/47866/gm_43l_v6_owners_rattled_by_engine_noise.aspx