Light knocking

[acolella76]

Hi guys, I am getting a little knocking sound coming from my engine. It only happens at light load between 2750-3500 rpm, never at idle and never at high RPM or WOT. As some of you may know I haven't had good luck with M20s and rod knock... but this doesn't sound like rod knock. Or maybe it is. That's why I have you guys!

I've been comparing it to what I remember of rod knock before my M20B28 blew up. First of all the B28 didn't drive for several weeks after the knocking started (I've put well over 100 miles on the car since the noise started). This also sounds a little lighter if that makes any sense. I tried to get a video but you can't hear the knock over wind noise while the B28's knock was very audible. Also it hasn't really hindered the engine's performance at all... it still sounds and drives great, although it does smell a little rich at times.

Now, I am leaning towards rod knock. I am working on getting a motor swap lined up. BUT, I would still like some more opinions. Discuss.

[redlightpete]

I had an a2 jetta with one bad crank journal. One rod would knock at even or light throttle around 3k rpm, kinda like you're describing. I drove it like that for years, until I eventually burnt a valve in that motor. Every time I changed the oil I would replace that one rod bearing and it would get a little quieter. Luckily in that car you could change a rod bearing in under an hour!

[Ether-D]

Yeah, my m20 just started doing the same at light throttle. Big chunks of copper in the oil pickup. I bought a replacement yard motor...

[Wschnitz]

Make sure its not a tranny issue, my i thought i had a rod knock on start/3krpms/letting clutch out but im pretty sure its a loose throwout bearing or uneven clutch wear

[acolella76]

Yeah, my m20 just started doing the same at light throttle. Big chunks of copper in the oil pickup. I bought a replacement yard motor...

Damn... I'm going to change the errrl today. Hopefully it isn't full of metal.

Make sure its not a tranny issue, my i thought i had a rod knock on start/3krpms/letting clutch out but im pretty sure its a loose throwout bearing or uneven clutch wear

That crossed my mind! What's making this difficult is the fact that it only occurs under load and not while in neutral... otherwise I could use a stethoscope to find the noise. But yeah I'd be really happy if it's just something in the tranny.