Diagnosing front axle vibration

Hi all! We are having a pretty unusual vibration whose origin my mechanic and I can’t pick up. In the following video I go at 60mph(100km/) and is already vibrating, then I brake and it shakes wildly. Down below what we have done so far (without getting to a conclusion yet)



Symptoms:
• Nasty outback highway, very hot and dusty, frequent potholes therefore frequent sudden stops and bumps, car loaded. Suddenly the brakes go fluffy, the pedal reaches the end. I stop for 1 hour, gets dark and fresher; the brakes are still softer than usual but work. I get back to town.
• Go to the mechanic, change the pads. The front axle now vibrates strong when breaking at 60mph and over. After that, the vibration stays for a while, then goes, then comes back (always when breaking, but sometimes even not breaking, just out of the blue, always around 60mph)
• after the pads replacement and the rise of the vibration, I also changed the hydraulic rack and the brake disks (rotors). We reviewed the callipers (which were dirty) and the lines, no visible issue. Also unplugged the ABS. The vibration reduced, but still arises sometimes - always at around 60mph and when breaking first, then stays for sometime- so that I guess it source hasn’t been fixed yet. If I stop the car 30minutes it would generally go away, but then as I speed up on the highway comes back.

What the heck could it be?

 

Did the mechanic swap the rotors? Warped rotors will cause that vibration

 

we did rectify them twice and it didn’t work, so I put new rotors but the issue persists

 

Tossing out a few ideas...

You didn't mention if you checked the tires for balance. Also, did the vibration just start all of a sudden or has it slowly gotten worse and worse? For example, say you went off-roading and afterwards thats when the vibration started, maybe you have mud stuck to your wheels causing them to be out of balance? Something along those lines.

The brakes going soft means the calipers are overheated and the fluid is starting to boil in the brake lines down by the calipers, the brake fluid vapor in the lines is what makes the pedal spongy. You have to find out WHY your brakes are overheating. Constant use with a heavy load could do it, but when driving they should get plenty of airflow to cool them down quicker than parking the vehicle - but ya, safer to park it than driving with soft brakes.

After you replaced the brake rotors, did you follow the break-in procedure for them? If you just started normal braking immediately (or in your case braking heavily), you might have warped the new replacement rotors, causing the same problem. Also, the hubs might be damaged enough to be out of round a little, causing vibration.

And lastly, if your front suspension or steering (tie-rod) bushings are badly worn, it could be causing oscillation in the steering, resulting in a vibration as well. You can check for excessive play in the wheels by (with the front wheels jacked up off the ground) grabbing the wheel in front and back (9 oclock and 3 oclock positions) and push and pull back and forth as if you're trying to turn the wheel by hand. You should not be able to see any perceptible wheel side to side movement. While you're there, do the same test but grabbing the wheel at 12 oclock and 6 oclock position, to see if the wheel bearing has excessive play, is less likely since if there's enough play in the bearing to move like that, it's probably already making audible noise indicating it's bad.

Hope these ideas help.

 

Hi! Thanks for your very valuable feedback, I appreciate that.

The rotors had been already rectified a few times so it was anyway a good idea to change them.
I did a complete balancing of the tires, alignment included. After I put the new rotors, I had the mechanic to put back the old pads (after being sanded and evened out) to see whether perhaps the new pads were defective and.. still there is the issue.
I am observing very closely to what happens, which really is that something does get heated up as I drive. It might be the calliper, it might be the wheel bearing?
As the issue worsen I am observing a progressive friction into the front axle, there’s a resisting force caused by friction, heat and swelling of a mechanical part. It goes slightly humming as I drive and get to the highway at 50-60mph, and when I brake it makes the steering wheel vibrate. Once again Injust changed the hydraulic rack too, so it must be something in the calliper or wheel bearing. We checked the brake lines and are soft. I had unplugged the abs.
Everybody says is not the wheel bearing because there’s no play, but might that just be lacking lubrication and then heat up and swell? I asked the previous owner and he hasn’t touched it in 10yrs/100k km and me neither in my 30k km to date. What do you guys think?