jeffers

Hoping someone can help with this - just went out at lunch time and the car has started making a rattling noise when coming off the throttle. Havent had chance to look at it properly yet but I'm hoping its not a TCT issue.

Its a metallic rattling noise which appears when coming off the throttle - i.e. when the engine returns to idle. Happens when out of gear when stationary and whilst driving. It disappears once the revs stabilse. Almost sounds like an old diesil van for half a second, if that makes sense.

Will check it a bit more in depth when I get home but does anything spring to mind? Its a UK MY04 with ~45k on the clock.

Thanks
Jeff

PedroHicken

Does it happen around 3000rpm?

jeffers

hmm, havent checked. what would that indicate?

Looking at some of the tech forums it could be something as simple as the cat/exhaust rattling.

PedroHicken

Im not exactly sure. I have the same so you wont be alone if it is, im quite interested to find this out myself.

Btw, probably completely irrelevent but my car runs fine.

jeffers

Yep, my car seems to be running fine too - although I did only go a few miles out to get some lunch. Hoping its just something loose and rattling. I'll report back once ive had a look.

If anyone else has any suggestions in the meantime they'd be much appriciated.

Jeff

sound_wave

Mine makes a resonance at 3k, which i think is a cat heatshield.
It also makes a noise similar to the one you describe (sounds like a playing card in a bicycle's spokes) but mine happens if you are either sat in no gear with you foot lightly on the throttle, or if you are slowly moving off.

NineBolts

Cat...

Does it do it from cold?
if not how quickly does it start happening?

The exhaust will heat up quite quickly so if it's OK when cold but starts happening within a minute of starting then look towards something exhaust related.

with a gloved hand if doing it on the hot car, give the various stages of the exhaust system a good slap, enough to wobble the system not enough you hurt you hand. heatshield, cat or centre box would be my guess>

If you have an oem exhaust system then I would say there's a good chance it's the cat breaking down. if an aftermarket exhaust might be the baffles in the center section or rear boxes.

jeffers

Difficult to say but i think its worse when hot.

Just got home and got the car over the pit - noise seems to be related to when the gearbox/manifold vibrate. Happens at different parts of the rev range but does seem reasonablly constant at 3.5k rpm. Oddly it cant be heard when the bonnet is open - no idea why, sound deadening?

Checked and the oil was slightly low but the noise is the same after a quick topup. Cars booked into my local specialist on Friday (Mike at R-motion) but I'm getting a bit worried. Not sure if I should stop driving it.

Any advise?

GaryB

The cat heat shield is the most likely cause. It doesn't sound like something to worry about.

s2k4tony

If it was the TCT, there would be the noise on idle. An ailing TCT can also make the chain rattle on the guides as you climb the rev range, perhaps if the oil is very low or poor quality from degradation.
My TCT makes a slight noise after being ran for a while when the oil drops to the halfway point on the dipstick. Soon as I top up, the noise goes. Sometimes though, I swear I can hear it whilst driving down the motorway next to the fastlane barrier (any car noises rebound off the barrier... try it!). Paranoia is a horrible thing when it comes to timing chain noises.
I'm considering sandblasting the wormgear and inside the piston myself, I will get my own sandblasting kit I think, instead of hastling a bodyshop to do it for me.
Like Gary says though, not much to worry about there for yourself