What's this sound? 97 850R (Video)

ArchieBrown · Post by **ArchieBrown** » 27 Jan 2012, 22:04

Hi contributors,

Ever since I've had my R it's had this little rattle. It comes on when its the car is hot, generally after some highway miles - and now I think I've finally captured it on video.

It's loudest when listening from the bottom of the engine, which I hope you will hear in all its little rattle glory in the second half of the clip.

Video here

There are no other symptoms other than this sound. The car still has ballistic acceleration and blows no smoke under power (or not). The sound isn't there on start-up or while the engine is cold.

Its got regulation level oil (synthetic) and its been serviced regularly but seeing as I'm about to spend some tax return dollars at FCP I thought that if this noise is due to a part I can easily replace, its best I do so now.

As always, your responses are greatly appreciated.

Thanks

Arch

Post by **rspi** » 27 Jan 2012, 22:20

It's hard for me to tell. Does the sound go away when you rev the motor or does it get faster as the rpm's rise?

ArchieBrown · Post by **ArchieBrown** » 28 Jan 2012, 02:03

I've just got back from checking to find it does both. The sound increases in frequency and pitch up to about 2000 revs and then quickly disappears.
It doesn't seem to get louder as the engine gets louder.
Could it be a loose shield or covering or something similar?

Post by **rspi** » 28 Jan 2012, 12:22

Sad to say but it sound like a low end cam train rattle to me. You may have a cam bearing going out. Be gentle and ride it out as long as you can.

You can always take it to a shop or two to get a few other opinions.

ArchieBrown · Post by **ArchieBrown** » 29 Jan 2012, 02:07

Thanks RSPI.

I've been googling solid looking for some kind of similar problem that may give me a parts list to consider, without much luck.
Both the R and my wife's 850 SE are due for a service, so I guess the shop will have the final say.

Thanks again.

Arch

Post by **precopster** » 29 Jan 2012, 05:54

Hi Arch, Would almost say it's an exhaust leak, possibly at the flexible coupling or the flange gasket.

If you run your hand around the flange with the engine running can you feel exhaust leaks? Hope it's a littly for you.

I have a spare flange gasket here if that's the issue and they're not too difficult to DIY if the car is allowed to cool.

Cheers Mike

glowbug · Post by **glowbug** » 29 Jan 2012, 16:36

it was a rather short video but it does sound like a exhaust issue, you can take a soild piece of wood or a extra long screwdriver and place it on the valve cover while holding the other end up to your ear, work your way around to each cylinder listening for (out of round) or not a smooth running top valve train. You will be able to pick out a bad valve, cam bearing or other right away. I am almost sure it is a exhaust issue, as you accelerate the engine torque causes the engine to slightly twist and apply pressure to the exhaust and therefore sealing the crack or leak? It is a longshot but like I said it was a short video. Let us know the out come. thanks and good luck