Technical What's that new droning noise?

[bugsymike]

What an interesting way to approach this. I'd never have thought to do this. Do take some pictures so we can all understand better how you're doing it.

Some years ago at an garage closing down auction I bought a case with all the professional kit to do just that, it wasn't wireless back then, but had four microphones and lengths of wire connected to a control box and speakers so it could be fixed to various parts of the vehicle and then you could isolate where the noise was coming from.
Sadly as I never used it I sold it on.

 

[bugsymike]

The sound effects on the Bullit car chase are amazing, they're dubbed on of course but who cares when they're that good! lol

Now if they used that on EVs to artificially make them sound like real cars...........
Mind you probably get a few more speeding tickets.

 

[Pugglt Auld Jock]

Now if they used that on EVs to artificially make them sound like real cars...........
Mind you probably get a few more speeding tickets.

Nah, forget all that, Just listen to this:



Possibly one of the all time great engine noises!

Did you notice the fly off hand brake? wonder what an MOT tester would make of that today?

 

[bugsymike]

Nah, forget all that, Just listen to this:



Possibly one of the all time great engine noises!

Did you notice the fly off hand brake? wonder what an MOT tester would make of that today?

Did sound great, even though a very nervous driver, although not as nervous as I was, when a young apprentice around 1970 when after fitting a new metal brake pipe and unable to bleed brakes on the outside fixed ramp made it necessary to reverse it down a concrete slope, whilst pumping the brake pedal, unable to adjust seat to reach pedals properly and yanking the handbrake on only to find it was the "fly off" racing type and rolled the car over the edge of the slope so both rear wheels were hanging in fresh air whilst car sat on it's twin silencers!!!
The really nervous bit was explaining to my boss what had happened, fortunately for me we managed to get it back on the concrete using some planks of wood etc. the only damage was a couple of creases in the silencer boxes.
Sadly I never got to road test.

 

[Zardo]

I recorded the four wheels, however the wireless microphone pair unfortunately only records mono, so I had to record one wheel at a time, and the quality wasn't as good as expected. The left rear wheel was a bit louder than the others and the humming noise was easier to hear in both rear wheels rather than in the front where it was basically absent.

Also, while driving down a hill, I pulled the handbrake, this made disappear the droning noise completely whilst the car didn't slow down (the rear wheels still spun), and when I released it, the droning noise came back at the same level and frequency.

But braking with the foot brake slows down the car and the droning noise and frequency both get weaker respective lower and stay weak at the same volume and frequency when the brake is released.

I now think that for a third time in 250 000 km, the rear wheel hub bearings have gone bad, especially those of the rear left wheel. The fact the noise appeared suddenly when accelerating hard is counterintuitive, however it's possible that when accelerating hard in 4th gear at almost maximum RPM the weight of the vehicle shifts to the back so maybe this contributed to it.

I ordered a pair of SKF VKBA 6541

 

[bugsymike]

I recorded the four wheels, however the wireless microphone pair unfortunately only records mono, so I had to record one wheel at a time, and the quality wasn't as good as expected. The left rear wheel was a bit louder than the others and the humming noise was easier to hear in both rear wheels rather than in the front where it was basically absent.

Also, while driving down a hill, I pulled the handbrake, this made disappear the droning noise completely whilst the car didn't slow down (the rear wheels still spun), and when I released it, the droning noise came back at the same level and frequency.

But braking with the foot brake slows down the car and the droning noise and frequency both get weaker respective lower and stay weak at the same volume and frequency when the brake is released.

I now think that for a third time in 250 000 km, the rear wheel hub bearings have gone bad, especially those of the rear left wheel. The fact the noise appeared suddenly when accelerating hard is counterintuitive, however it's possible that when accelerating hard in 4th gear at almost maximum RPM the weight of the vehicle shifts to the back so maybe this contributed to it.

I ordered a pair of SKF VKBA 6541

If pulling the handbrake on made the noise disappear surely that indicates it is a a fault in the handbrake side rather than a wheel bearing?
Possibly a broken cable if vehicle didn't slow down, I had something similar on a Skoda 4x4, it felt like a broken handbrake cable as the hand brake lever came up a long way, but it turned out to be the rear brake caliper self adjusting mechanism had failed, so a new brake caliper.

 

[Zardo]

If pulling the handbrake on made the noise disappear surely that indicates it is a a fault in the handbrake side rather than a wheel bearing?
Possibly a broken cable if vehicle didn't slow down, I had something similar on a Skoda 4x4, it felt like a broken handbrake cable as the hand brake lever came up a long way, but it turned out to be the rear brake caliper self adjusting mechanism had failed, so a new brake caliper.

Thanks. The caliper on the left side (rear) was replaced about 6 months ago with a refurbished one because of zero braking action on the left rear wheel, because the self-adjusting mecanism was broken. The handbrake braking action was tested afterwards and passed the official test just fine (I posted a thread on this in this forum).

Pulling harder on the lever did make at least one tyre screech on a rainy downhill road and this screeching noise isn't helpful when assessing the droning noise, that's why I didn't pull the lever of the handbrake too hard. I also didn't intend to lose control when pulling the handbrake at 65 km/h going down a hill in the rain.

Also the goal was to avoid slowing down the car since the droning noise decreases in volume and frequency with decreasing speed. So it would not be clear if the droning noise diminished because of decreasing speed or because pulling the handbrake. That's why I had the car rolling down a hill in neutral and pulling the handbrake a bit kept the speed steady.

The car has disk brakes on all four wheels, pushing the caliper against the disk might stabilize play in the wheel bearings and therefore decrease wheel bearing noise as long as the handbrake is pulled whilst driving.

And the forces acting on the wheel also shift when braking.

 

[bugsymike]

Thanks. The caliper on the left side (rear) was replaced about 6 months ago with a refurbished one because of zero braking action on the left rear wheel, because the self-adjusting mecanism was broken. The handbrake braking action was tested afterwards and passed the official test just fine (I posted a thread on this in this forum).

Pulling harder on the lever did make at least one tyre screech on a rainy downhill road and this screeching noise isn't helpful when assessing the droning noise, that's why I didn't pull the lever of the handbrake too hard. I also didn't intend to lose control when pulling the handbrake at 65 km/h going down a hill in the rain.

Also the goal was to avoid slowing down the car since the droning noise decreases in volume and frequency with decreasing speed. So it would not be clear if the droning noise diminished because of decreasing speed or because pulling the handbrake. That's why I had the car rolling down a hill in neutral and pulling the handbrake a bit kept the speed steady.

The car has disk brakes on all four wheels, pushing the caliper against the disk might stabilize play in the wheel bearings and therefore decrease wheel bearing noise as long as the handbrake is pulled whilst driving.

And the forces acting on the wheel also shift when braking.

Surely if brakes working correctly both wheels should try to lock on applying the handbrake?
Hopefully all will be revealed on inspection.

 

[Pugglt Auld Jock]

Surely if brakes working correctly both wheels should try to lock on applying the handbrake?
Hopefully all will be revealed on inspection.

Hmm? yanking the handbrake on at 65km/hr on a wet road surface whilst going down hill could have resulted in a very "interesting" experience?

 

[bugsymike]

Hmm? yanking the handbrake on at 65km/hr on a wet road surface whilst going down hill could have resulted in a very "interesting" experience?

Where is your sense of adventure?

 

[bugsymike]

Where is your sense of adventure?

Many times over 50 years ago as youngsters we used to do handbrake turns with our old cars and a bit of accelerator, obviously rear wheel drive and old cross ply tyres, plus empty roads helped a lot. Mind you I did get caught out one morning doing that on a stony lane, got back on the main road, van driving strange, checked and I had caught a sharp stone which had caused a cut right through the tyre around a good 18 inches of the tread right through the tubeless, so instant deflation and time to fit the spare. All part of the learning curve.

 

[Zardo]

Is there any improvement for mitigating the design error which causes premature rear wheel hub wear and tear by water and dirt ingress in some Punto Evo cars? I can't believe that this issue hasn't come up more on the fiat forum. Does it only concern cars with rear disk brakes, which are not too common for Fiats?

The original bearings (car was new) lasted not even 50'000 km, they were replaced and a lot of lithium grease was added at the time, but the second set also got destroyed after another 50'000 km. (Mileage by memory) Therefore a third set was installed, using the approach mentionned in this german-speaking Abarth forum, which cited a solution found for Opel which apparently shares the same platform (as pertaining to the real wheels), and their Opel-internal solution is called "Feldabhilfe 2500". So when my car had around 100'000 km I ordered those O-rings from Opel (as shown in the solution) and installed them to help prevent water and dirt ingress. I also lubricated those O-rings with plenty of Castrol LMX lithium grease (green stuff) and put additonal grease into the bearings. This helped to increase the lifespann of my rear wheel bearings to 150'000 km.

But now they are gone again.

Now in the german forum someone argued that putting an O-ring in isn't the best solution because of the lateral circular shape, the lateral contact area isn't 2-dimensional and he proposed to install a flat seal instead, like this (I don't know if it really fits well): https://www.kugellager-express.de/v-ring-ringdichtung-va-70-63x75x11-mm

Anyway, I'm now wondering if I should go for the flat seal instead, or just re-order those O-rings. Will it really matter since the car has 250'000 km and other stuff might fail before it reaches 400'000 km?

 

[AnthonyH]

Is there any improvement for mitigating the design error which causes premature rear wheel hub wear and tear by water and dirt ingress in some Punto Evo cars? I can't believe that this issue hasn't come up more on the fiat forum. Does it only concern cars with rear disk brakes, which are not too common for Fiats?

The original bearings (car was new) lasted not even 50'000 km, they were replaced and a lot of lithium grease was added at the time, but the second set also got destroyed after another 50'000 km. (Mileage by memory) Therefore a third set was installed, using the approach mentionned in this german-speaking Abarth forum, which cited a solution found for Opel which apparently shares the same platform (as pertaining to the real wheels), and their Opel-internal solution is called "Feldabhilfe 2500". So when my car had around 100'000 km I ordered those O-rings from Opel (as shown in the solution) and installed them to help prevent water and dirt ingress. I also lubricated those O-rings with plenty of Castrol LMX lithium grease (green stuff) and put additonal grease into the bearings. This helped to increase the lifespann of my rear wheel bearings to 150'000 km.

But now they are gone again.

Now in the german forum someone argued that putting an O-ring in isn't the best solution because of the lateral circular shape, the lateral contact area isn't 2-dimensional and he proposed to install a flat seal instead, like this (I don't know if it really fits well): https://www.kugellager-express.de/v-ring-ringdichtung-va-70-63x75x11-mm

Anyway, I'm now wondering if I should go for the flat seal instead, or just re-order those O-rings. Will it really matter since the car has 250'000 km and other stuff might fail before it reaches 400'000 km?

What you'll find with after-market parts is that sometimes they fix/mitigate for known design faults.

You could buy several bearings manufactured by different companies and you'll likely find some brands have done the fix.

Recently i replaced a strut mount on my Fiat 500X, the original strut mount had a rubber band around it that in this case allowed the ingress of sand. The after market strut mount i bought didn't have this rubber band, it was replaced by a solid plastic construction.

I can't answer your question with any precision, but I think getting 150,000KM out of bearings is actually good so i'd be using the O rings again.