My Evo is making some noise. I'm worried about spinning a bearing. I'd like to hear what people here think are the symptoms of rod knock and a spun bearing. I'll describe my symptoms after I hear a few opinions.

Thanks.

 

Hmm, probably the easiest way to describe rod knock is that it sounds like someone is lightly tapping the side of your engine with a small hammer; a very metalic knock. It will also happen with the same frequency as your RPMs (fasters revs = faster knocks). The last part is that it usually gets louder when you stress the engine and will quiet down when the engine isn't being pushed.

Once you've heard it and know what it is, it's hard to mistake for something else.

 

Thanks for the input. I'm still not sure if I've got a problem or not.

I spun a bearing on an old '85 911 I used to have. That motor had 118,000 miles on it. When it developed a problem I could hear knocking just as the engine was unloaded after accelerating. In other words I could modulate the throttle at pretty much any RPM point to get it to knock. But that engine was a flat six, maybe it showed slightly different symptoms.

In the case of the Evo I *think* I'm hearing a knock above 3K RPMs and it's pretty much constant regardless of load condition unless decellerating, then I don't hear it. For all I know the noise has probably been there since the beginning and I learned to tune it out. Recently, since I've installed my mods, I've become more paranoid and far more sensitive to the noises the engine makes. I guess it will get worse if I truely have a problem.

Anyone have any idea how much a new crankshaft costs?

 

Sorry about over explaining, I wasn't sure how mechanically inclined you were. Guess I shold have taken a better look at yor mod list. If you've had the head or valvecover open I'd ask about cam knock or a collapsing lifter.

I had an Acura V6 engine develop a cam knock on me once; it was like rod knock only much quieter. Unlike your issue, it went away at higher RPMs and was more noticeable at idle.

 

If it's a rod knock, there's no way you could miss it. It's a loud clunk, clunk, clunk sound. It sounds much better when you wine up the throttle a little, that clunk-clunk noise gets louder and faster.

 

Thanks for the advice guys. You're right, the rod knock in my old 911 was unmistakable. I think I'm getting paranoid. Oh well, paranoia is just a heightened state of awareness.