Metallic like rattling noise when pressing hard on accelerator

[kasku25]

Hi All. Hope you are well. I have bought my Mercedes A200 2013 back in August 21. Recently, it has started making metallic like rattle noise when I press hard on accelerator. The noise is not there when car is parked or idling. The noise is not there everyday, it seems like when I fuel up the car to like 3/4 then the noise is not there at all. Any ideas what it could be? I have got this car serviced (major service) back at the end of October 2021 and they haven’t told me about any issues at all with the car.

Thank you in advance!

 

[LostKiwi]

Probably a loose exhaust heat shield

 

[Droverunner]

Yep my first thought LK even before I scrolled down to see your comment. Hope it's so as a cheap easy repair compared to many "what's that rattle" issues.

 

[joderest]

Is the vehicle a petrol ? if so could be "pinking" caused by weak mixture (air leak ?)

 

[mioba]

Yep my first thought LK even before I scrolled down to see your comment. Hope it's so as a cheap easy repair compared to many "what's that rattle" issues.

my thought too reading the post.

you can either take off offending part of the shield, or any exhaust place will weld it if good metal.

 

[LostKiwi]

Pretty common for the heatshield to corrode around the clamping washer. The 2asher grips a metal stud and push fits in. VW do an oversize one that pushes straight on to fix it.

10x Volkswagen Metal Locking Star Washers- VW Underbody Heat Shield Fasteners | eBay

We try to make sure our photos are as clear as possible so you can identify the correct parts.

www.ebay.co.uk

 

[kasku25]

Is the vehicle a petrol ? if so could be "pinking" caused by weak mixture (air leak ?)

No, it’s a diesel

 

[Manc Rick]

Try to pinpoint where the sound is coming from. Sounds extreme but I pinpointed a noise recently by sitting in the boot while my son drove the car carefully. Immediately became obvious.

Is it coming from the front (turbo area?) or the fuel tank (you mention it seems ok when full of fuel) or the rear (pointing towards exhaust)?

It’s not easy to pinpoint noises as sound travels and can be very deceiving but I would try.

Just some non-expert ideas from someone who has spent a lot of time chasing noises over the years!

I agree it does sound like it’s likely to be heat shield / exhaust related, although that doesn’t explain why the noise appears to not be there when 3/4 full of fuel.

 

[brandwooddixon]

I'd vote for a loose heatshield or exhaust clamp at first. If you can get under the vehicles its easy to check. Tap the clamps with a small hammer as often they'll rattle into a position where they get wedged until they work their way lose again.
I've fixed heatshields in place using "old penny" washers, typically 25-30mm diameter with a small central hole, liberally coated with instant gasket on the heatshield side and pushed into place over the holding stud.

 

[00slk]

My lose exhaust heat shield was an easy find, rattled at idle and when slowly accelerating. Though you could hear the noise from outside the car. Tried the o/s rear shield first, bingo, the washer had worn through so fitted a larger washer and all is well

 

[brandwooddixon]

Yes. The rears tend to go first as they don't get heated and thus dry out as quickly as those further towards the front, hence exacerbating the electrolytic corrosion that takes place between the aluminium heatshield and the steel retaining fixing.