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Hey all - Here's an odd one that has had me stumped.
Vehicle: 2015 Ford F-150 XLT SuperCab 2.7L eco with 6r80. 173K on odometer. Transmission overhauled at 150K.
Symptom: A slight hum/vibration (Almost identical to a wheel bearing hum) ONLY when brakes are lightly applied. Noise audibly appears to be originating at the passenger front. Other technicians who have ridden passenger front have been able to feel it (again, only when brakes are lightly applied.). Noise correlated with wheel speed. Noise diminishes as more pressure is applied on brakes. Nonexistent under hard braking.
This seems to have been occurring for nearly 15,000 miles and has been to 2 shops already without luck in pinpointing concern.
Tests already done:
- 4WD tests: 4WD system operates 100% normally under road test. Putting the vehicle into 4WD or removing the vacuum from IWEs DOES NOT eliminate this noise. - In air: 2WD / 4WD selection works 100% normally when vehicle lifted and driven in air. At idle, IWE's unlock. Front wheels spin without engaging axles. In 4WD, all four wheels receive power normally. - Stethoscope: Driving the vehicle in the air in 2WD or 4WD did not reproduce the sound at any speed, or at any wheel. Neither when accelerating nor lightly braking. - Vacuum checks: Have vacuum tested system. At the check valve, the peak vacuum was registered at 30 inHg. When lightly braking, the vacuum dropped to 15-20 inHg. So replaced the vacuum check valve. --> No change in symptoms. Checked the vacuum at IWE's and the vacuum level seemed normal. IWE's locks and unlocks normally. - Visual: IWE's under visual inspection have no issues. They are not falling apart nor is their unusual wear on the teeth. No play in any of the wheel bearings. Calipers pins and piston all move with relative ease. No seized brake components. - Parts Cannon: As the vehicle already had 173K, front pads & rotors were nearing the end of life --> Replaced front pads & rotors with Akebono. This did not change the noise. In a last-ditch effort, both front hub bearings were replaced as the noise really does sound like a hub bearing, except for it only noises under like braking. Again, neither of these parts corrected the issue.
Myself and many others are lost. Has anyone experienced anything similar on an F150? Is there something I have overlooked within the IWE system?
Maybe loose front end components: ball joints, tie rods etc. I have seen worn control arm bushings cause rhythmic vibrations while breaking that you would swear are rotational in nature.
Problems with the caliper, sliders or bracket mounting hardware. Maybe even rust built up inside the arch of the caliper that only interacts with the rotor while applying pressure.
Wheel problems like an unevenly worn tire, or under torqued lugs maybe even ovaled out lug holes in the rim.
I have even seen front driveshaft U-joints sound like bearing noise, but the front driveshaft is on the left, you are reporting right front noise.
Yes – double checking the basics is incredibly important. Unfortunately, everything on this truck is tight. Tie rods, ball joints, control arm bushings, etc. Wheels get hand torqued to spec every time they come off. Tires have worn incredibly evenly. No feathering or cupping.
As far as brakes go; calipers compress and decompress freely. No indication of a collapsed brake hose. I always file, or sand blast the mounting brackets and apply fresh sil-glyde to the caliper pins.
Friday, I disassembled the assembly and manually vacuumed the IWE operation. It locks and unlocks properly. Lines will even hold a vacuum long enough that I do not suspect them as being leaky.
I will keep digging into this periodically as I have time. Although universally everyone agrees the noise / sensation is primarily felt in the passenger's front's feet – I wonder if this is a case of noise resonating from possibly the rear through the frame. Perhaps I should just invest in chassis ears.
You can pinch off one front brake hose at a time and see if the noise/vibration changes or goes away. Do this at your own risk, of course. Do the same for the rears if you still think the issue might be resonating from the rear. I don't love pinching off hoses, but I have yet to damage one while using a clamp like this:
Thinking along the same lines as chassis ears, there's also NVH For Android. The app won't localize the noise to one corner of the truck or another, but it'll give you a better idea of the noise frequency and where to start looking.
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