Mystery sound on my 2.2

[James S]

My 2.2 (non-sport) is making a sound somewhere between a creak and a rattle with wide open or near wide open throttle between 1600 and 1800 rpm. It's happening in all forward gears (not in neutral), but it's hard to tell where it's coming from when driving. I'd say under car (driver's seat) if I had to place it. No noticeable effect on performance.

I thought someone on here might have an idea what it is. I'll update this thread if I find a solution off the forum.

 

[mrscalex]

I get a noise like a bird chirping. And I’m fairly sure that’s my rear drop links.

That could easily sound like it’s coming from under the driver seat.

Although your noise sounds more aggressive. Broken spring?

Anyway, if it’s really coming from that area it’s not going to be the engine unless it’s throwing the sound.

So I would think suspension (might be front) or possibly propshaft.

 

[James S]

The sound was there around the time of the last MOT and it's only under those particular engine conditions so I don't think it can be a broken spring.

Something to do with the prop shaft maybe? My gut feeling is that it's drive train related because of the link to high engine stress and that rpm range...

 

[Jack Ratt]

I'd check all fasteners are fully tightened. I had a rattle on my Merc at low revs and on tick over. It sounded like loose exhaust baffles so I was preparing myself to buy a new exhaust.
I was doing some pre MOT checks and when I gave my rear box a good shake I noticed that the heat shield above my exhaust was a little loose. Once everything was tightened it's been as quiet as a church mouse

 

[James S]

Thanks for the suggestions. I'm getting the car up on axle stands this weekend so will check for anything broken or loose.

 

[Cooper]

It could be the start of what developed in 'tunnel slap' for me. Exact same conditions but far worse than what you are experiencing. This can be caused by a failing Guibo disc [flex disc], failing central support bearing for the prop shaft, or in my case it was actually the U joints in the prop shaft that were starting to bind.

Not that I went through everything and as a last ditch effort I pulled the prop shaft out and took it to a professional. He fiddled with it and said it seems fine to him. I demanded that he put it under full load and test it which he did, that was the problem! Rebuilt it and I all those issues are gone.

I noticed that many people went down this road and when they say they are taking the shaft in for repairs the thread went dead - a sure indicator that it fixed the issue!

Cheers.
Cooper