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Mystery Knock


eric_454
04-05-2011, 03:53 PM
I have a 97 3.1 here that knocks just like a rod knocking. I dropped the pan and the rods didn't look bad, but showed a little wear (no brass) so I slipped in a set. Knock is still there and it gets louder (REAL loud) when you pull off the #1 plug wire. If it ain't a rod what is it? Piston wristpin? I can actually FEEL the knock with my hand on the intake but can't really hear it well; I'm a little bit on the deaf side. This little engine runs great and never gives any trouble at all, I'm even still driving it. Just knocks like crazy and sounds like it's gonna fly apart at any second. Any insight?

inafogg
04-05-2011, 05:07 PM
did you use a stethiscope or simular,oil pressure ok?

eric_454
04-06-2011, 10:08 AM
Not a stethy but I got a tire iron I use for that. Best I can say is it sounds like a hammer on the bottom of the intake. EVERYONE around here says it just has to be a rod, but I've just been there it's not a rod, least not the big end. Pulled the rod bearings out to look and they seemed fine. I slipped a set in thinking it might just tighten it up but the noise didn't change. It does hold good oil pressure by the guage. Sure gets loud when you pull off the #1 wire, though, and only on #1. I guess I'm just gonna pull it out and tear it down.

thephantom1492
04-06-2011, 05:35 PM
What about the hydraulic lifters?

eric_454
04-06-2011, 06:01 PM
Well, pulled the head off after work and #1 has enough piston-to-wall clearance to drive a truck through! I'll get the pan off in the morning and knock out the assembly for a better look, but I'm pretty sure as of right now the noise was a piston slap from Hades. Looks like I'll be boring this one. I don't know how it didn't just smoke like a chimney.

inafogg
04-06-2011, 06:56 PM
think you found the noise!
how many miles are on the engine Eric??

eric_454
04-07-2011, 11:12 AM
Odometer reads 144,174 miles. Pulling the pan as we speak, pretty close.

eric_454
04-07-2011, 04:24 PM
Well, Got the #1 rod and piston out. There was a little noticable play in the wristpin to piston (enough that I'd think it would make noise) so the local engine guy got me another piston on and I'll be slammin' it back together in the morning. His used piston was about a thou bigger than mine and should take out some of that slack too. I know it's a Band-Aid but I really didn't wanna bore this little jewel anyway. If it lasts a couple three more years or till the trans quits I'll be very pleased!

eric_454
04-13-2011, 04:58 PM
Well, it's not fixed. Got all the stuff and put it back together and the noise is STILL THERE! Resized rod w/piston, new rod bearings throughout, and it still has the same noise. Absolutely unchanged. Knocks like a rod then knocks REAL loud if you pull off #1 wire. I don't know what could possibly make a noise like that besides a rod, but it sure ain't a rod. They measured right on the money and like I said the bearings didn't even look bad to start with. Mains looked great. Didn't see anything that looked bad in there maybe the cam is broke, I dunno. I'm done with it though, not spending anymore money on it. Auction time. Thanks for the input and opinions.

inafogg
04-13-2011, 05:25 PM
SORRY TO HEAR ERIC,
it did sound like you were on the right track
any chance for a video or audio?

inafogg
04-13-2011, 05:49 PM
Eric, read this bullitin #57-61-24A
making sure you read the entire bullitin
or until it gets your attention!!!!

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