Single Knock When Braking

MadBrit · June 12, 2017

I have a 2006 IS220D I have recently had all new brakes pads / shoes Including hand brake and discs.

It is now making a CLONK when I brake, just one CLONK, O/S Front I think, I took it back and that said there is nothing wrong

Now it makes a nasty metallic knocking when i drive along and the slightest bump sets it off, if I put my foot on the brake when I drive along it seems to get better.

I took the wheel off and was surprised that the wheel is the only thing keeping the disc on, I presume this is right.

The caliper nuts are tight, but a bit of play in the sliding caliper part.

What can this be, do I need a service kit ?

Thanks

G

The-Acre · June 12, 2017

Something has to be loose/worn/ not fitted properly. The fact that it makes one clonk when you apply the brakes suggests it. In many cars the wheel holds the disc on, sometimes there's a countersunk screw.

Farqui · June 12, 2017

Did this knock occur before the recent brake changes?

Some brake pads aren't such a snug fit in the caliper and can knock.

Does your car knock when braking going backwards, then again when going forwards? I've had this on other cars and found changing the pad and pad manufacturer solved the loose pad knocking.

Linas.P · June 12, 2017

5 hours ago, MadBrit said:

I took the wheel off and was surprised that the wheel is the only thing keeping the disc on, I presume this is right.

The caliper nuts are tight, but a bit of play in the sliding caliper part.

So you already identified your problem - knocking most likely is resulted by loose slider pins.

That is right disc is only held in place by the wheel, as such it is very important to properly clean your hub before putting the disk on (with wire brush or if you very pedantic with medium sandpaper). This is something many indies skips on - I know because I usually stand by their side while they are doing it (so they do it properly).

Another point - did they replaced anti squeal pads/shims? That could result in pads being slightly loose, but I guess you would have extremely annoying squeal as well.

is 220d owner · June 12, 2017

brake pads fitted incorrectly , is it originals or cheap ones? do you allways hear the noise when braking? or is it just after leaving the car over night?

Shahpor · June 12, 2017

Does the noise only occur under braking or does hitting a bump also set it off?

If it does it when hitting a bump, then it could indicate that the problem could be suspension related.

Of course, a loose brake pad is also just as likely

MadBrit · June 13, 2017

In answer to questions, it only happens when going forward and it only started after the brake service, I have taken the wheel off again and I noticed that the top pin on the sliding part of the caliper, is a little loose in its sleeve, can I just replace the pin or is it a complete caliper ;(

Thanks for all your help

MB

MadBrit · June 13, 2017

does anyone know of a good workshop manual I cam buy / get for this car ?

MB

is200 Newbie · June 13, 2017

You have said the knocking is from the front brakes.

There is a rubber grommet/washer installed on one of the pins on each or the front calipers. If the wrong type of grease is used then it will react with the rubber grommet over time and it will be impossible to get it back into its housing if taken out and anyone servicing the brakes may leave it out. I actually think its there to prevent knocking.

If you reverse and brake and then move forward and brake then I am guessing you get a slight knock - this is more that likely the brake pads showing they have a bit of play in the guides. Its not an issue and just something to expect if using non OEM brake pads. Some don't make the noise, some do.