Rattle - help!

[halbe01]

Hi all,

I thought this problem worth throwing out there as its driving me nuts!

On a 2005 4200 CC I have a rattle which is rather spoiling an otherwise lovely car. It comes from outside, somewhere under the car. It's a tinny metallic fast clanking sound which happens at about 1400 revs. Above that it seems to pretty much disappear, though not completely. Oddly its pretty unpredictable - sometimes it's loud and sometimes it's quieter, and sometimes (rarely) it not there at all. Once the car gets properly hot its pretty much gone though. As many of my journeys are short I spend a lot of time listening to the rattle. It's certainly easily loud enough to be heard by passing pedestrians who might otherwise have been thinking 'nice car'... so a little embarrassing in town centres.

The car has been in to the local shop (Autofficina) a couple of times and they've spent some time investigating and trying fixes, including designing and fitting a bracket to the exhaust heat shield,that being a likely culprit. However it's not fixed the problem.

Has anyone else had annoying rattles which might be similar? Any ideas appreciated as if I can't get this resolved I'll probably be looking to get rid of the car (which won't be cheap as I'd then need another car and a GS would be the obvious purchase!)

Cheers,
Ben.

 

[Emtee]

Ben, does it rattle with the car stationary? I take it Autofficina have checked the exhaust mounts as well as the heat shield?

 

[halbe01]

Thanks Miles - a very interesting point - I don't think it happens when stationary however it's entirely possible that it does and I just never rev the car in neutral. Will test it tomorrow. One other part to the puzzle is that the ratle is definitely worse when pulling away from stationary and turning at the same time - ie when pulling out of a junction.

I'll mention exhaust mounts when it next goes back in, but they do seem to know their stuff so my expectation is that anything obvious (assuming that is - I'm no mechanic!) they'll have checked.

Cheers
Ben.

 

[Parisien]

The other dangerous type of noise from under the engine area is a noise like small stones rattling around inside a tin can.....meaning a catalyst break up......I too had the vibrating heatshield, which my mechanic, experimented on over the space of an hour....6/7/8/9/ different positions etc and it eventually cleared....it too was only noticeable when at idle.........and when you mention "clanking" then it sounds more mechanical/transmission.....need it seen to again Ben, hoping its nothing much!


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[conaero]

It sounds like the cats to me too. As the car gets up to temp, the metal expands and the rattle stops. You need to get this looked at ASAP as there has been the odd issue with the material from the cats breaking up getting sucked back up into the engine, and I am sure you can work out what happens then.

Best to be safe than sorry with this one.

 

[Parisien]

If it is...all is not lost, instead of putting on very expensive Maser exhausts/catalysts, will have the excuse to up-grade to larinis!!!!


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[halbe01]

Larinis a little expensive for me - but on the Performance Italia site they also have the FD ones which are considerably cheaper. Any experience of those anyone? (I'm jumping the gun here, but still very curious as to the differences). The sound I'm hearing is much more "bit of metal resonating and hitting something else metal" than "stones rattling in a tin" so I'm not expecting it to be that.

B.

 

[conaero]

Not heard of FD producing their own exhaust before, just checked it out on PI, very interesting.

Might be worth a trip over to Maseratilife.com in the states to see if anyone has fitted them.

Larini are expensive but worth it IMHO.

 

[Emtee]

Larinis a little expensive for me - but on the Performance Italia site they also have the FD ones which are considerably cheaper. Any experience of those anyone? (I'm jumping the gun here, but still very curious as to the differences). The sound I'm hearing is much more "bit of metal resonating and hitting something else metal" than "stones rattling in a tin" so I'm not expecting it to be that.

B.

Hi Ben, Did you find out whether you have the rattle when stationary in neutral?

You mention it occurring at around 1,400 rpm. Is this true regardless of gear when moving? If so then it might point to some sort of resonance. Can you tell whether it's front or rear of car? Do you get it only with the engine cold?

 

[dem maser]

Surely if its the cat then "that" garage would have noticed it.....id be ****** if so....

Im not technical so ill leave these guys with you on this one but hope its not expensive....

 

[BennyD]

I've goy Larini cats on mine and they seem to work well. Even with the inordinate amount of crackling, popping and banging it does on the overrun they seem to be hanging in well. As Matt said; expensive but worth it, especially with the life time guarantee.

 

[halbe01]

Morning all,

So having not been certain if it does rattle when stationary, I checked last night and it definately doesn't. So it's only when moving, and while the loudest noise is around 1400 revs, it does do it a bit at other revs - with another (quiter) spike in rattle noise around 2-2,500 revs as well. So resonance makes sense there, it's just figuring out whats resonating being the challenge!

To be honest I can't really tell where it's coming from - I think it's nearer the rear, but that's my judgement from sitting in the drivers seat and I'm not sure you can really tell when the sound has to travel forwards to get in through the window anyway!

The noise does disappear when the car gets properly hot - after 30 minutes or so of driving. It didn't do it at all round the track in Llandow (though at full revs it'd be drowned out by the engine anyway, despite only having the stock exhaust!).

One last piece of the puzzle - the rattle seems worse when turning corners! So something obviously shifts a little with the g-force of cornering - or perhaps something (correctly) bends slightly - and the rattle is more pronounced.

Any other thoughts or ideas would be very welcome - I'll print off a copy of the thread to give to Autofficina in case any of the ideas from here might be something they've not already thougth about.

Many thanks,
Ben.

 

[NoC]

My car is currently in the shop for the same tin rattle. One of my precats is rattling. Check your cats or shield.

 

[Gixerboy]

Hi there, sounds like Loose baffle to me, if u have a rubber mallet, try gently hitting the tail pipe, I had a similar noise on my QP, the noise travels along the exhaust making it difficult to place. The fact that it is more noticeable when pulling away & turning , would support the resonance theory when under load.
Hope that helps
Dave

 

[Parisien]

Welcome to the UK forum NoC..........

A bit early there isn't it??!!

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[Emtee]

Yep, from your additional information I'd agree with loose exhaust baffle. As Dave mentions (backed up by not getting it whilst stationary) it's load related. Once warm, the sonics of the exhaust change considerably. I have the Larini's so I can hear the effect more and the sound when warm is completely different to when cold.

 

[NoC]

Haha, thanks
Always up late cuz I do a lot business in china.. I am on mlife but it seems like the uk forum has lots of great info. I am glad I am here!

Welcome to the UK forum NoC..........

A bit early there isn't it??!!

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[Parisien]

Excellent......China is the way to go........ML is a good site too, some very passionate and able Maseratisti on there too!


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[halbe01]

Thanks for all the ideas guys - will see what they find when it's back in the shop. Not sure whether the idea of it being inside the exhaust pleases me or not - it means a simple exhaust upgrade will solve the problem, but then again that's not a cheap thing. I'm still spending quite some brainpower on what exhaust changes to make - but that's a whole other topic! Larini backboxes are too loud at idle for me, I've not yet seen a valved Larini backbox to judge if that would be right for me, nor a Tubi though Loz did offer to come listen to his, and I see differing opinions on the sonic qualities of replacement cats and H and X pipes. Still, half the fun is in the research... and the other 90% is in the driving of a car with just the "right" sound.

Cheers,
Ben.

 

[conaero]

Halbe, if you take the day off and go to ProSpeed in Wales, he will build you an exhaust for about £600 in stainless. PM Pat/MaserSod for details.

http://www.sportsmaserati.co.uk/showthread.php/1905-My-modified-GranSport?highlight=prospeed