GTS Noise on start up

[smg800]

Hi all,

I didn't want to hijack the QP Rattle on start up thread, so here goes;

Does anyone else with the GTS 4.7 get an odd rattling sound coming from the exhaust when first starting the car up? It only happens when it is cold out, and only happens the first time I start the car. To explain that a bit better, I can start her up and then after about 5 seconds I will get a metallic rattling sound from the exhaust for about a minute I guess whilst it also chucks out quite a lot of fumes, then it settles in to normal.

If I then drive off, stop the car, leave it for a few hours and start it again I don't get the same sound. I have only noticed this since it has been really cold! So it is just the first start of the day.....Just me or anyone else?

I got a bit of a weird bang on pulling off earlier too which made me wonder if the handbrake was stuck on, but it wasn't so I am just pretending it didn't happen for now

 

[Felonious Crud]

Hmm.. I'd have said that the pulling-away clunk is almost certainly the handbrake being stubborn about letting go. They're prone to sticking so I tend not to use mine - set it to park brake off when I leave it for any length of time, unless on a hill where belt and braces seems prudent. Why do you think it wasn't the handbrake?

The exhaust rattly thing would sound normal if it lasted for a few seconds. Mine does it and I checked with the main dealer who said all normal, not to worry. I *think* it could be the exhaust valves closing. They do it more quietly when there's a decent build up of pressure. Why it would take a minute I'm not sure. Do they open and close ok with the sport button? Give 'em a blast with WD40 and see if that helps loosen 'em up a bit.

Sorry for the technically inept answer. I'm trying to remember what causes the rattle and all I can think of makes only partial sense. But I wanted to share it anyway.

 

[EXCF350]

For the last few weeks mine has only been driven at weekends and when the temperature has been hovering around freezing. No unusual noises when starting. The brakes do clunk when I set off for the first time as they have seized over the week - and that's with it being sat with the parking brake off - just normal for this time of year.

Is the rattle from the baffles? Have you tried switching to sport mode to see if the rattle stops? Have you given the baffle mechanism a good squirt with WD40 to make sure it operates correctly?

 

[EXCF350]

Sorry for the technically inept answer. I'm trying to remember what causes the rattle and all I can think of makes only partial sense. But I wanted to share it anyway.

Well that makes two technically inept answers then! I was typing mine while you answered with the same conclusions....doesn't mean we are right though!

 

[Felonious Crud]

Maybe two wrongs do make a right. I'm happy with that. We are geniuses! Or even genii.

 

[conaero]

Your rattle is the valves in the rear boxes mine did it too. Clean them up with some WD40 but don't worry about it.

Take it out of sport and the noise will stop.

 

[smg800]

Thanks for the advice thus far;

Adam - it could have been the handbrake to be fair, in fact I imagine you are right! I guess I thought it wasn't as my previous handbrake issue had very different symptoms (you may have seen the thread on it, I had a slight catching sound as I drove along which culminated in a bang whilst driving and it turned out the handbrake had been jammed partially on and the brake pads delaminated - I have had a new handbrake (pads, discs, cables, hub etc) courtesy of Marios since!). The fact this was very different (you summed it up nicely by saying it sounds like the handbrake being stubborn about letting go) made me think it wasn't the same problem, but in hindsight it probably was but with a slight variation if that makes sense. I need to take your advice, a couple of others have said they simply don't use the EPB. My drive is on a slight slope but should be fine if I leave it in gear.

EXCF & Conaero - it does it whether in sports mode or not, I have tried switching between the two to check. When you refer to the baffle mechanism and the valves, do you mean the mechanism that opens and closes/switches between sports mode and normal? If so they have had about a gallon of WD-40 on the weekend as at one point sports mode stopped making a difference to the exhaust, i.e. hitting sports mode put me into MC Shift etc but the exhaust stayed mute. Copious WD 40 fixed that problem, are we talking about the same mechanism or do I need to get back under there and find something else? The rattling existed before the sports mode problem, and has continued after.

Many thanks for the advice again, you may have gathered that mechanics aren't my strong point so apologies for any terminology faux pas's that may have been made

 

[conaero]

In the pipe there are butterfly valves that work like a carburettor, they rattle and that will be the cause.

You can start the car up and push something up the tailpipe and stop it to make sure its this doing it but you can see them rattling too.

 

[bigbob]

Sounds conclusive. I just wish the valve control mechanisms were not exposed as they stop working every winter and need WD40. Is there a way I could enclose them?

 

[Felonious Crud]

In the pipe there are butterfly valves that work like a carburettor, they rattle and that will be the cause.

You can start the car up and push something up the tailpipe and stop it to make sure its this doing it but you can see them rattling too.

Those valves must be in addition to the "volume control" valves controlled by the sport button, is that right Matt?

 

[EXCF350]

Sounds conclusive. I just wish the valve control mechanisms were not exposed as they stop working every winter and need WD40. Is there a way I could enclose them?

I've not looked too closely but maybe some sort of rubber gaiter could be wrapped round with some zip ties. Only thing it would have to cope with the heat and not trap moisture in there. Maybe smearing with grease would suffice

 

[bigbob]

Like the sound of that, surprised no one makes a kit especially for Northern England/Scotland where salt application to the roads is rather liberal.

 

[conaero]

Those valves must be in addition to the "volume control" valves controlled by the sport button, is that right Matt?

Yes mate that's correct.