Humming noise

QI have a question about my 2017 Vauxhall Insignia 1.6 CDTI SRI VX line. The car is making a strange humming noise from the rear. The noise and its frequency varies depending on the cars speed and the noise definitely relates to wheel rotation speed and not engine speed.

I have removed the wheel that sounds like where the noise is coming from, and the discs and pads are in quite poor condition. A large lip on the disc and when spinning the disc after removing the caliper and spinning the disc I can see the disc is slightly warped and there is a tight spot and I presume this is what is causing the humming and why the humming varies depending on vehicle speed.

The caliper looks like I need one of those proper brake caliper rewind tools.

I’m considering getting one from Amazon as one is reasonably priced. My concern is the car has one thing I hate on modern vehicles which is one of those awful electric handbrakes. Can I simply rewind the caliper to fit new rear discs and pads or do I need to put the car into some kind of service mode or something?

The disc is stuck on the car well. I didn’t really try to get it off as I didn’t have a new one to put on. What process do you use in that scenario? A puller the size needed to remove a 292mm disc would be quite expensive I presume.

If I do decide to tackle this job myself,

I will probably do the front discs and pads as well – the front discs have a corroded lip as well. Are they straight forward as long as I remove the brake fluid reservoir cap and keep an eye on the level as the caliper is rewound? I presume I’ll need the caliper rewind tool on the front as well.

I think COVID and lack of use of the car due to working from home for a while has contributed to this situation. I do leave the handbrake off though when I know the car isn’t going to be used for a while.

I’m considering paying a garage to do it but I like to learn and do things myself. Sorry to send you so many emails but I really appreciate your help and advice and I like to learn as once the kids are grown up, I plan on buying cars with faults cheaply, repairing them and hopefully selling them for a small profit as a bit of a hobby/beer money thing. Ian Turner

AThe rear brake caliper piston does only need pushing in when replacing the brake pads and should not be turned or wound in. The procedure does not need any specialist equipment and is carried out as follows:

▶ Service mode is activated by switching the ignition on – then firmly depressing and releasing the brake pedal five times. Then depress and hold down the brake pedal and press the EPB switch until the EPB malfunction warning lamp in the instrument pane flashes, then release the EPB switch.

▶ Press and hold the EPB switch for five seconds, then release the brake pedal. The EPB malfunction warning lamp in the instrument panel will extinguish briefly. The service mode can also be set using diagnostic equipment if available. The process of removing the rear brake calipers can now be carried out. When the brake calipers are removed and you have ensured that there is room in the brake reservoir to accept any returning fluid, the caliper piston can be pushed back. This should NOT be rotated.

The torque settings for the rear caliper carrier to hub is 100Nm + 23degrees, and the torque setting for the rear caliper to carrier is 47Nm. Once the new pads and discs are in place and the caliper is refitted then the brake pedal should be pumped up until firm, then the service mode should be deactivated as follows: ▶ Ensure the ignition is switched on, depresses and hold down the brake pedal, pull and hold EPB switch until EPB malfunction warning lamp in instrument panel is extinguished.

Then release the brake pedal and switch off the ignition.

It is quite common for the brake disc to become adhered to the hub flange due to rust and corrosion, the best method to remove the disc is to apply a penetrating oil to the flange and then as the brake discs are being replaced, using a hammer to tap them off, should free them from the flange. This of course would not be possible if the brake discs were to be refitted as the use of a hammer on the face will cause distortion.

When the brake caliper is removed I would also carefully check the hub bearing for any resistance as this is one area that could well be the source of the noise you can hear. A hub bearing will often make a humming noise which is adjusted by the speed of the vehicle.