E30 M50B25 Non vanos loud knocking/rattling

[sascha 17]

Yesterday I was on my way to go get some oil and a filter, and when I was about 5mins down the road the engine started making this loud knocking/rattling noise, as well as cutting out whenever I took my foot off the throttle.

I pulled over as soon as it was a safe place to stop, turned it off, and got a tow home in fear of damaging the engine further.

Started it up today to take the video and now it idles, but still has this very unhealthy sounding knock. Sounds almost like there's something come loose that's being thrown around in there.

It's roughly proportional to engine revs, but isn't perfectly regular.

Any ideas what this could be? Trying to organise a tow up to HellBM soon, but in the mean while it'd be great to get some ideas.

Here's the video, sorry I don't know how to embed it in this post. The noise is louder than it sounds in the video, and maybe a little less 'tinny' sounding.

https://www.youtube.com/watch?v=HpHlbiNq1h4&feature=youtu.be


Thanks in advance

[Evo30 6]

Sounds like my e30 1.8 now, after I over heated the engine. The big end bearings wore out.

I hope that's not the same issue you got.

[Allanw 1052]

The symptoms make me think differently, but the video sounds like a spark plug may have stripped and been blown out. Worth a look.

[sascha 17]

Sounds like my e30 1.8 now, after I over heated the engine. The big end bearings wore out.

I hope that's not the same issue you got.

That was what I had in the back of my mind too, hopefully not!

The symptoms make me think differently, but the video sounds like a spark plug may have stripped and been blown out. Worth a look.

Thanks, I'll check the plugs this afternoon.

The timing chain was always a bit rattly, is it possible that it's stretched so much that it's jumped a tooth and now the timing's off? (Not sure if that's a feasible idea, I'd imagine the chain would have to be pretty loose to do that!)

Alternatively, is it possible that this could be an oil pump failure? (Although if that was the case then I'd imagine the oil pressure light would always be on, which it isn't)

[e30ftw 396]

Hmm yikes! Not sounding too good.

Was it low on oil at the time, I had that sump and pickup modified higher when I broke it so it's about 40mm higher and probably lost a litre of capacity so if it was low it could have been lower than you thought, either way that could have contributed to it (seemed like a bright idea back then since it was sitting very low in the front).

[sascha 17]

Nah the oil's pretty much full, maybe 1mm under the 'full' mark on the dipstick.

Ha yeah I'm glad you had the sump modified, otherwise it would definitely be smashed by now!

Edited September 5, 2014 by sascha

[KwS 2378]

The symptoms make me think differently, but the video sounds like a spark plug may have stripped and been blown out. Worth a look.

This is actually the first thing i thought of too when i heard the video. Quick and easy to check.

[yng_750 247]

Is it just me or did the knocking not increase in speed with the engine.

I have had a spark plug blow the center out. Made a hell of a noise but more of a chuffing than knocking. Was in a sohc mitsi so could sound different.

Ive also had big ends go which sounded a little different.

Im taking a random stab at a main bearing.

Check plugs i guess. Then pull sump if you are keen. Main or big end will still have a sump full of metal.

[KwS 2378]

pull plugs and then drain oil, bit easier to drop oil than the drop pan and should be obvious if youre suddenly panning for gold.

Either way, stop running the engine until you know what it is.

[sascha 17]

Cool thanks guys. I've checked the plugs and I think they're okay.

I've spoken to Ray and Sam up at HellBM and I'm arranging a time to tow it up there, so hopefully we can get it sorted soon.