Wierd metal "hissing" noice from the Engine (M42

[frankiez]

Hello,

Could you please advice me regarding this wierd noice that can be heard when driving 3000-4000 rpm. It's sounds like metallic hissing against each other.

It can be also heard during idle speed.

I already swapped the timing chain tensioner, no help. Then I tried to listen the source of the noice with a screwdriver. I placed it directly to the timing chain area (cover) but I don't think that the noise comes from there.

As I was moving my head over the engine block my finding was that it was around middle of the engine top of intake manifold?

IS it necessary to adjust manually valves in M42?

Can anyone help, where is that noice coming and is it serious?

[Templ8e30]

The valve clearances are automatically adjusted on the M42 with hydraulic tappets.

It's not an air leak is it ?, I had a hissing sound on my 2.7 and it was a collapsed intake manifold gasket.

Cheers,

Iain T

[cliffybabe]

i was gonna say inlet manifold gasket

[frankiez]

Ok, lets assume its manifold gasket. However, should not there be somekind of signds of bad idling if the is a airleak in the manifold

few questions; if the timing chain is worn or the nylon thing that that pushes, should it be heard clearly with a screwdriver? I'm not sure if the word Hissing is best to describe the noice since english is not my native language.

Anyway it sounds like two metallic parts is parts are touching is other, not a scricing sound. Hard to describe.

More ideas or comments?

Thanks!

[Chris-W]

The metal shield for the HT leads above the exhaust manifold - is it fastened on tight?

[frankiez]

The metal shield for the HT leads above the exhaust manifold - is it fastened on tight?

"The metal shield for the HT leads" hmm, what is this one`and where it is located, pic anyone?

E30 (and m42) is totally unknown to me, so I really appreciate your efforts to help!

[Chris-W]

Exhaust side of the head, above the manifold; just follow the HT leads from one end to the other and you'll find it in the middle.

Held on with two nuts/bolts. Can cause a high pitched rattle if loose.

[Templ8e30]

http://www.realoem.com/bmw/showparts.do ... g=12&fg=05

Number 3.

Cheers,

Iain T

[frankiez]

I found something:

1) I tried to tighten the nuts in the heat plate --> no effect. I think it was tight already.

HOWEVER, when I put me hands on the top of the intake manifold and leaned on it (almost all my weight, 200lbs) it went silent, the hissing sound disappeared?? If I pressed left or right side of the manifold, no effect. Only by pressing from the center it went silent?

Wierd? But relief I think? So, it is not anything serious and I can go to track tomorrow? ;)

[dodgem]

Weird that you can hear it at idle....

My 318iS makes a metallic noise at 2500 to 3500 revs but i've never noticed it at idle. Thanks for the diagram Temple, i'll check that when it's back from the garage as i've heard people suggest it before but never knew exactly where the heatshield was.

If you figure out what's causing it any further frankiez then do please post here

[frankiez]

Well, have ever tried to listen it hood open? I did not notice it at first time?

[Brianmoooore]

HOWEVER, when I put me hands on the top of the intake manifold and leaned on it (almost all my weight, 200lbs) it went silent, the hissing sound disappeared?? If I pressed left or right side of the manifold, no effect. Only by pressing from the center it went silent?

Sounds even more like an inlet gasket - sealing up when you lean on it.

[frankiez]

HOWEVER, when I put me hands on the top of the intake manifold and leaned on it (almost all my weight, 200lbs) it went silent, the hissing sound disappeared?? If I pressed left or right side of the manifold, no effect. Only by pressing from the center it went silent?

Sounds even more like an inlet gasket - sealing up when you lean on it.

Well, just one thing worries me. Could it explain the noice when revving in 3000 and upwards?

To my logic in might since the flow and leak grows when rpm gets higher?

[dodgem]

It might be two different noises....

As i said, i've never noticed the noise at idle, but a "metallic hissing against each other" noise describes my mid-rev-range noise quite well. Maybe the gasket is damaged and that's what you hear at low revs, at higher revs, teh sound of air escaping may be drowned out by the engine but then at 3000rpm you hear the new noise?

[frankiez]

Well, it might be so...It's just my wishful thinking.

Well, I'm heading to the race track today, lets see whats gonna happen!

[Martinaston]

Are you sure its not just the hissing noise of the air squeezing past the throttle ?
It tends to echo inside the inlet manifold.