Hi All,

I've got a hollow metallic rattle on my '95 X306 that comes in about 1500RPM and seems to go away above about 2000RPM, or at least is drowned out by the rest of the engine. It's not a loud or intrusive noise, indeed you only really hear it when driving slowly with the windows down past fences etc, where the engine sound can be reflected back to you,

The engine starts quiet hot or cold, there's no timing chain noise on startup, it starts quiet and smooth every time. The closest I can describe it is a kind of rattle/scraping noise like if you were dragging a screwdriver lightly against a rotating flywheel.

I don't THINK it's the timing chain as the pitch of the noise doesn't change with RPM, the pitch of the noise stays constant and it disappears completely below about 1500RPM. To me it sounds more like a resonance, something involving sheet, to give it that metallic tone.

I've yet to investigate closely, but wondered whether it could be a heat shield on the exhaust manifold or perhaps a catalytic converter or baffle inside the exhaust broken loose.

Anyone else had something similar?

Here is a video of the noise I'm hearing:

 

I would get the car up on stands climb under it and give everything a good shake. Hopefully you'll find something loose.
Last year I found my exhaust heatshields had a few loose bolts and were causing a kind of high pitched rattle over light bumps and like you only heard when driving alongside a wall.
Finger crossed it's not the catalytic converter.

 

I had been planning on eventually decatting it anyway. Not a legal requirement here. At 27 years old, I suspect the Cats are likely past their best anyhow.

 

You posted in the X300 forum BTW.
I guess we get the same kinds of issues.

 

I've added a video up showing the noise

 

That doesn't sound good. It sounds like the exhaust rattling. But before you order a new one I would check that the engine is playing nice.
I assume you're not getting any DTC codes, but are you able to check what the short and long term fuel trims are and if you are getting the 4g/s from the MAF.
Also what condition are the coils and spark plugs and are the throttle body, EGR and idle control valve clean and working?

 

No codes, car is running absolutely flawlessly, no stumbles or misses. Coils seem good, as far as I can tell everything seems clean and working well. Fuel consumption is spot on so clearly not running out of sorts. Noise seems to be more of a vibration rattle than anything else, sounds louder on the right hand side of the car than the left so would seem closer to the exhaust.

 

Timing chain? What mileage have you done?

 

Only on 120,000km. Has the later upper chain tensioner.

Would have thought the noise was too tinny / jangly for timing chain, and there is absolutely no noise on start up at all. Also only over a 500rpm rev band and it dies away quickly as revs drop below 1500.

Not saying it isn't, but I would be very surprised as it is. I have listened to dozens of timing chain noise videos on YouTube snd nothing sounds remotely like this.

 

I think we likely have a culprit. Definitely exhaust, I think the heat shield around the downpipe, at least that is how it appears.

Need a second person to blip the throttle while I am under there to confirm




If this is the culprit, how easy is it to remove and refit this shield? I can't imagine it is supposed to be that rattly.

 

I didn't remove the heat shields on mine, I just tightened up the loose bolts. I suspect it would be tricky to remove them without removing the exhaust first.
Did you see anything that could have worked itself loose under there?

 

Well it doesn't seem to be the heat shield, had a look under the bonnet while someone else revved the car. Initially thought it could be cam chain as it sounded like it was coming from that area but a screwdriver on the front of the engine seemed to indicate it was pretty quiet. Going to pull the header heat shield off tonight to check for cracked manifold, as that is a potential, and of course it could be a broken primary cat inside the downpipes still. Will investigate further.

 

Well, looks like it is the timing chain after all. Sound confirmed coming from the cam chain underneath the front of the cam cover.

Will get a new set of tensioners and guides ordered. Part of me is tempted to just replace the top tensioner and see how that goes but I think I should probably bite the bullet and make a day of it over a weekend and replace the whole set of tebsumioners, guides and dampers.

 

Great that you found it, It's time to get get inside and operate.
Haven't worked on the tensioners yet, but I'm kind of expecting it at some point.

 

Just to follow up on this, pulled it to bits over the Christmas break and it seems like my cat may have used up one of its nine lives. See the video below. This was the primary (lower) timing chain. Looks like the tensioner has seized.

I was just going to replace the tensioners and dampers but given the chain has been whipping a fair bit, I figured I will replace the chains as well. Think that involves some special tools i don't have so will ask in another post i think.