[Grumpymonkey]

Good morning all,

We purchased our I30 two years ago and have thoroughly enjoyed the driving experience even though it has over 100000 miles now it drives beautifully. We have an issue that it is very concerning. When driving for a small distance, approx 4/5 mile at speeds over 50/60 mph a very loud knocking sound becomes evident. Drive 30/40 mph all week and it is silent. Very difficult to pinpoint the location however the knocking decreases/increases with the speed of the vehicle. After being stationary(lights/roundabout) when setting off again the noise disappears! Had a mechanic look and the wheel bearings are all silent, bushes in good order nothing obvious underneath nothing loose. The noise is VERY loud and alarming.

Grateful for advice and comments in advance.

Craig (Grumpy and getting grumpier)

[TerryT]

While waiting for one of the forum's tech gurus to post, do you have a sense of where the noise is coming from, e.g. front, middle or rear of the car?

[TerryT]

Random thoughts. If you can beg, borrow or steal a 6-channel automotive electronic stethoscope (google it) and hook its six transmitters under the car you will likely locate the source through its headset while driving.

In the old days, troubleshooting would also include checking the tailshaft and universal joints . Did your mechanic check them (or equivalent for i30)?  Presumably you bought the car secondhand?

[Shambles]

I'd also check the exhaust fittings.

[TerryT]

I'd also check the exhaust fittings.

Yes . I should have thought of that to say.  Loose/broken exhaust hangers can let part of the system bang against something...can be as noisy-as.  As can loose/worn swaybars and end links.  But it sounds like Grumpy's mechanic has hand-checked the obvious things and should have found anything loose or picked up on any damage or shiny marks/scuffs from something rubbing/hitting underneath. Maybe it's a vibration issue at certain revs?

Here's a link to an automotive electronic stethoscope I mentioned previously.  I have the same brand, mine is wireless with 6 transmitters.  How to Find Car Noises Fast - YouTube .  The video author (Scotty Kilmer) sounds a bit over the top in his presentation, but I think he knows his stuff.

These stethoscopes sound gimmicky but I've used them on mine and on mates' cars many moons ago and they can be useful for quickly locating those hard-to-find noises that occur only when driving.  They beat having someone lean out of an open front/rear door while driving at speed and listen for the noise.  The Highway Patrol here do not like that...neither did my wife when I suggested it.

[TerryT]

Good morning all,

We purchased our I30 two years ago and have thoroughly enjoyed the driving experience even though it has over 100000 miles now it drives beautifully. We have an issue that it is very concerning. When driving for a small distance, approx 4/5 mile at speeds over 50/60 mph a very loud knocking sound becomes evident. Drive 30/40 mph all week and it is silent. Very difficult to pinpoint the location however the knocking decreases/increases with the speed of the vehicle. After being stationary(lights/roundabout) when setting off again the noise disappears! Had a mechanic look and the wheel bearings are all silent, bushes in good order nothing obvious underneath nothing loose. The noise is VERY loud and alarming.

Grateful for advice and comments in advance.

Craig (Grumpy and getting grumpier)

Criag (Grumpymonkey).  Did you identify the problem?