Knock-knock, who is there?

[my1stgn]

So im getting some major knocking/rattling noise at idle (engine is a 3.8 Series II used on the W-Body cars) Above 1500 rpm it goes away, at idle its pretty loud. Sounds like marbles or something. As you rev it it goes away. In gear above 1000 rpm it is pretty much gone. Still drove the car and it drives fine (but obviously there is a problem) thought it was the supercharger coupler so I took it off and tore it apart. Looked good, already has green upgraded coupler. Re-installed, same noise. Took of the s/c belt. Still makes noise. Cylinder walls look good and compression is over 150 on all cylinders. Taking apart bottom end. My question is, how much does the rod bearings have to be worn before they start making noise? Im going to put in new bearings but the stock ones have some unusual wear but I dont know how bad this is. The rods where the bearings ride still have the hatch pattern on them so very little oil is back there. Anyone know how bad the rod bearings have to be before they make crazy noise? I will post up pics in a few. Thanks!

 

[my1stgn]

Okay so I doubt its the rod bearings. They look worn but not noisy worn. Ive seen worse bearings on these engines with no noise. But Ill take a second opinion from you guys. Also, where else could a knock at idle and not about 1000 rpm be coming from? Cylinder walls look real good and crank turns smoothly. Ive attatched some pics of the worst bearings, but they are pretty much all the same.

 

[jimski]

maybe cracked flywheel??

 

[86GN-862+2]

I just had a rocker shaft break. Before it broke, I could hear some knocking. I do not hear it after replacing the rocker shaft with another stock unit. My guess is that you only hear knocking at lower rpms which equal lower oil pressure. Lifters may be bleeding to fast down below and they get nice and tight after 1000rpm when oil pressure is up. I am not a mechanic but this would make sense. G/L!

 

[KL Mallender]

If it's the Harmonic balancer!!, do I win a cookie?

Kevin.

 

[jmendlik]

Knock

Does this happen when it's cold or only after it warms up? Does it lessin if you use thicker weight oil (20W-50) ??

 

[rmar]

Converter........

 

[WHEEZER]

Converter........

I'm thinking loose torque converter bolts too..

 

[87gnturbosix]

Piston

Did you check the wrist pin area. I had a hair line fracture that gave me a similar knock.

 

[Steve V]

Did you check the wrist pin area. I had a hair line fracture that gave me a similar knock.

Seen some pistons come part on these motors at work. People are uping the boost and not changing anything to compensate.

 

[drturbo69]

Knock Knock

Hows There Second Balancer-take Belt Off And Grab Balancer -see If Rubber Seperated.if So Balancer Is There Or Not.
Frank

 

[my1stgn]

I'm thinking loose torque converter bolts too..

Thats what I though before I pulled the engine. Checked them when the engine was still in but it was good. Im thinking balancer too and I had someone else mention this. If you want me to mail you a cookie, then yes you get a cookie! :biggrin: .... if its the balancer. Other items found worn was the timing chain wearing into the tensioner and the balance shaft had a lot of play. So I will keep you guys posted! Let me know if you have any other suggestions. Will check rods again tonight.

 

[86GN-862+2]

If I get it right, can I get a nice steering wheel ring for my '86 GN I say valvetrain is the culprit.

 

[my1stgn]

If I get it right, can I get a nice steering wheel ring for my '86 GN I say valvetrain is the culprit.

Umm, If I had an extra one and you were a little more specific like the lifters or rockers arms, then yes! but if your right, the most I could do is a cookie or something! lol