Harmonic Balancer moving

[rommaster2]

I'm posting this question for a friend who lives hours away and have limited experience working on an m20 so excuse me if this seems like a stupid question. The m20 has been making a terrible noise that sounded like it was coming from the bottom end, similar to a rod knock. After inspecting it closer it appears that the harmonic balancer has been moving and striking the timing cover.

The question that I have is what could be causing that? The engine runs fine apart from the the sound of it hitting the timing cover. Is there a bearing in there other then the crankshaft bearings that could allow that play or is it the harmonic balancer? My friend already replaced it with a used one and both make the noise so that doesn't necessarily rule it out since they were used.

Any help would be appreciated.

Oh and its an 87 325is with a stock m20b25

[digger]

There is a rubber portion bonded to steel that probably has partially failed delaminates. Stress, heat and time do that. It's not a big job to change it

[Kershaw]

I'm surprised your engine is still running. The CPS needs an accurate signal off the harmonic balancer for engine timing.

[rommaster2]

Yeah i'm surprised that it works still, literally my friend removed the lower timing cover and the damn thing runs perfectly pulls fine no issues at all apart from the slight movement allowing it to hit the timing cover and make a banging sound.

My friend is now thinking it may be the hub, for some reason this issue seems to be the one time i can't get it through to him to keep it simple and eliminate the basics for sure before you assume its something else.

[jeffnhiscars]

You'd think he would throw a belt