Noise from underneath W211

[milleplod]

There's a really.....really!!.....annoying noise coming from under my E280 CDI Sport, it's driving me barmy! It sounds like the exhaust is hitting against something once in a while - there's a definite resonance to the noise, it's not a bang or a knock, there's a 'ringing' element to it, if that makes sense. The exhaust is fine though , new hangers were recently fitted, it can't catch against anything. Sometimes, the noise is there as I'm just setting off in a straight line, at others it's at very low speed - it does it every morning as I turn left off the drive - there's a bit of a hump between drive, pavement and road....boinggg!! I've not heard it at higher speeds, but I suppose road noise could be masking it.

My mate's had the car up on his lift, we couldn't see anything obvious, nothing seems loose anywhere. I emptied the boot yesterday, nothing rattling around in there. Could it be indicative of a broken spring, for example? Or could some other worn suspension component generate that sort of noise?

Any suggestions most gratefully received!

Pete

 

[Gbrowncls55]

Could be the exhaust just a bit too close to the heat shield. The heat shields are a bendable material (aluminium I expect) and I have found on a number of mercedes, including a 211 E500 that if you go through a flood type puddle at any speed the force of the water can move the heat shield in relation to the exhast causing such a noise when the exhaust moves uner torque or cornering. Just getting under the car and bending it a little away from the exhaust fixed it in each instance. Just my experience.

 

[W1ghty]

I’ll throw a guess at broken spring as well

 

[Grahamcol]

Could indeed be a spring. I've had two rear ones go and in each case my car made a "clank" noise. The second time l had just purchased my CLK and l instantly knew it was a broken spring.

 

[milleplod]

Thanks for the replies chaps. I'd already posted about replacement rear springs a couple of weeks ago, something I was thinking of getting done, so sooner rather than later methinks! As a point of interest, I'd only had the car for about 6 months when, as I drove along a nice, smooth road, I heard a horrendous BANG!!!! from under the back of the car - I wondered what the hell it was, put it down to something that had hit the underside....even though I'd not seen anything in the road....and continued on my way. I had a look underneath when I got home, but nothing untoward could be seen. The sound of a spring going perhaps....?

Pete

 

[bolidemichael]

Could be the exhaust just a bit too close to the heat shield. The heat shields are a bendable material (aluminium I expect) and I have found on a number of mercedes, including a 211 E500 that if you go through a flood type puddle at any speed the force of the water can move the heat shield in relation to the exhast causing such a noise when the exhaust moves uner torque or cornering. Just getting under the car and bending it a little away from the exhaust fixed it in each instance. Just my experience.

This happened to me, however it was a gentle but definite clattering/reverberation audible at low (car park) speeds.

 

[Stratman]

If it sounds like hitting a tin bath with a crowbar, it's a spring

 

[milleplod]

If it sounds like hitting a tin bath with a crowbar, it's a spring

Good analogy! Mind you, I'd have gone for 'toffee hammer hitting a biscuit tin', but we're definitely on the same wavelength!

Regarding the heatshields - the car was at BJ Mason's in Sheffield a few weeks ago. Amongst other jobs, he fixed the heatshields on both sides of the system as they'd come adrift and were rattling/vibrating....another 'driving me barmy' noise!

Pete

 

[milleplod]

Another observation - it doesn't do it all the time....it's not done it at all today, not even when turning off the drive. Why would that be.....does something move that, for a while, stops the noise??

Pete

 

[Stratman]

The banging noise, if it is indeed a broken spring, is caused by the broken ends grating against other. When mine broke, the break was at the bottom of the coil, about two inches or maybe a bit less from the end. The coil sat normally in the lower cup, just maybe a quarter of an inch lower. Every now and then the stars would align and the broken surfaces would catch each other and then release, and this is what causes the noise.

If you do get underneath for a look, if it is broken at the bottom (a favourite place) it can be very difficult to spot. You need a good light and a mirror to see right into the cup. You may need to run a finger along the coil to feel the break, but be very careful as the break can have razor sharp edges.

 

[Smiley]

Check the dust plates behind the discs esp the front ones. The rivets break and then they bounce around. Makes a ringing sound as you describe. I will bet 10:1 it is the NSF plate that's gone so start there first. No need to take the wheel off just jack the car up and see if the plate is secure.