What could this noise be coming from the engine?

- Only does it on idle. When i accelerate it goes away

- Does it more frequently on a cold start

- Coming from intake side of the engine

First few seconds of the video the car is being slightly revved.



Any help is much appreciated. I'm hoping someone knows exactly what it is so i can order the parts ASAP..

Thanks
Steve

Use a hose (like a 5' section of garden hose) as stethoscope and isolate the source of the sound.

Of the things that make a sound on intake side, I can really only think of the disa rattling. I don't think that's your sound though. I'd say maybe check your tensioners/pulleys. It doesn't sound like a pulley, but check it out. If you notice the belt hopping up and down between pulleys, it probably is a tensioner.

Might be that something which was replaced got loose. What work did you have done most recently?

Very odd sound...never heard anything like that.

HTH

Possibly the PCV / crankcase, or one of the pipes partially blocked, maybe that's whats causing that pipe sucking sound?

Thanks guys. Damn I'm legitimately worried now that DMAX said he hasn't heard that sound before. The last thing I've replaced has been the intake Camshaft Pos Sensor. I had to move the intake a little but didn't take anything apart (followed the DIY on doing this). I havn't yet tried to locate exactly where the sound is coming from but from memory it sounded close to/around the oil filter. It's going in to the mechanic very shortly for a major service so I will get him to look at it..

Don't be worried that I haven't heard that sound before. Try the hose idea. Around where you think the sound is coming from is the ccv, as mentioned, and maybe it is that, though it sounds like the sort of sound I'd expect a bad bearing to make...sort of.

Also, if you've got a 'major' service coming up, maybe this is the time to try your hand at diying. There is lots in a major service you can diy quite easily.

Thanks Dmax, I swung past my mechanic so he could hear it and he too said it is most likely a bearing. I'm pretty sure this is an easy fix so I'm hoping its that. I have a major service coming up, I think it's at 100,000 kms. My car has 80,000kms but I've just put it up for sale so I'm going to get it serviced before I sell it for peace of mind. Bought a fuel filter, oil filter, spark plugs and Camshaft Pos sensor headers side. Going to get my mechanic to do it as I just don't have the time.

Good luck man, hopefully it's not something major

Have you taken out the disa to inspect it? It sounds like the butterfly's just dangling in there.

Originally Posted by udm-e46 enthusiast

have you taken out the disa to inspect it? It sounds like the butterfly's just dangling in there.

+1 disa

I don't even know what a disa is, I need to do some research. Car goes in to the mechanic tomorrow so I will let him know

Ok so had a look at a few other E46's with a Disa valve problem. I'm almost confident that the disa valve needs replacing as symptoms are low rpms on the odd occasion which is what I am also experiencing. Thanks for the help guys. I will let my mechanic know.

You should take out the DISA and inspect it before coming to any conclusions. It is literally a 5 min job to check and even replace.

Yup, DISA is super easy to check. I checked mine the other day for the first time at 122K and amazingly it's still going strong!

See DISA section in the first link below in my signature.

Thanks for the replies guys. My mechanic got back to me and he's located the sound - he said it is a bearing/tensioner from one of the main drive belts. Apparently my main belt had hairline cracks in it and needed replacing asap. Anyway, hes replacing the tensioner and the belt. Pick up the car in the next two days so hopefully my mechanic was correct. He said he pulled everything apart and could hear/see the loose bearing where the noise was coming from.