My wife has a 2000 Blazer ZR2 4.3. About a few weeks ago I had blew #5 rod bearing. Being unemployed I had to go the cheap way out. I found a junk yard offering a used 4.3 with 90k for 500$ everything looked well so I bought it and installed it.


A few days ago i was finished installing I did a really clean install everything came out real nice. Yesterday I was driving around testing everything making sure everything was good. I Noticed this funny rattling like noise it almost sounded like the left side exaust manifold heat shield was rattling. The noise started about 1500 and only with a load on it. Without a load everything was perfect and quiet as can be. I double checked every single thing nothing was loose. It almost sounds like it was internal. Could it be some kind of odd detonation noise? I am so stumped and not sure what to think..


In my tons of research on the internet i came across this (#03-06-01-024C: Rattle Noise In Engine (Install Timing Tensioner Kit)
What would this sound like and what exactly happens for this to cause noise? Also the tsb said 1800-2200rpm mine is more like 1500-2000


Thanks
-Bri

 

Well as for the TSB you mention that is more of a knock, I still really dont see how but at the 1800-2200rpm range the timing change apperently gets slack and causes the knock, hence why they tsb says to install the tensioner like the newer 4.3s have. They claim it doesnt damage anything but only time will tell on that note. Did you check all the plugs when installing that engine, if the previous owner went strictly by the maintance schedule recommendations those plugs are almost due to be changed.

 

I finally got around to checking the spark plugs. It was just about time to replace them so I did. No change in noise. The engine now has 400 miles since i dropped it in. It hasn't got any worse or better.

I just wish I knew what it was so i know if I have to pull this engine again or not lol.

 

not a chance that it is another spun bearing is it? I'm having that issue with my 98 right now and about to drive me crazy. Not looking forward to the irritating removal of the oil pan.

 

haha I thought I was the only one with that rattle. My 1996 has the exact same thing but its around 1700-2200 rpm. I think when it gets warmer and I have free time il do the timing chain and tensioner, Mines been doing it for over 30k

 

Its been 12k and 6 months since I have replaced the engine. Still running ok haven't had any major problems so far.

As far as the noise goes i have learned to just pretend its not there. I can still hear it I just don't think about it. It never was really loud and it has not changed in 12k miles.

I plan on not fixing it unless it gets louder in fact I think this summer ill put on a flow master and drown out that noise.

 

I know that it is a pain trying to find out what is wrong with the motor knocking but if ya don't fix it eventually it will get worse and with you just putting a new motor in it would it not be pointless to sit here and watch another one go to the wayside? Like i said I have the same problem with mine right now and I have found that the connecting rod bearing that sits between the crank and the connecting rod has moved over and began making it knock. It is VERY CHEAP to fix. bought the part for 3.00. Just drop the oil pan replace the bearing, and put the new one on.....If it is the bearing and you don't get it fixed it is just a matter of time before you score the crankshaft and it locks up on you completely. Be smart, take care of it while it's small before you have to go get the crank resurfaced.Pain in the A$#...

Got a question just PM me.

 

The thing is that its not knocking, its more of a rattle. Almost like a heat shield was loose or something but everything is tight and the rattle appears to be internal. Its only while the engine has a load on it and only at 1500 - 2000. Its not very loud at all and besides that the motor sounds very healthy. The motor that I took out had a #5 rod knock and sounds nothing like that.

I have searched long and hard for that noise. I gave up a long time ago. 6 months later the noise has not changed one bit. If the engine blows again that's fine I'm ready. I just hope its nice weather if I gotta replace it again

Personally I think its ok but I do have a feeling that TSB in the first post has something to do with it .

 

Mine has the same noise and it's being driving me crazy for months now. Like you say, you can't hear it unless the engine is under load. If you do find out what it is then please post it on here 'cos I'd love to know.
Cheers. Lee

 

Ours also does the same thing or close to it. We have driven ours for 51,000 miles with it. We just drive it carefully. We are getting ready to take it on a 3000 mile trip. We drive it off-road in areas that are hundreds of miles from people. Ours has never gotten any worse YET.