Knocking Potentially From Servo Or Master Cylinder

[chipstick 382 1 Cars]

My car has developed a knock when braking which sounds and feels likes it's within the bulkhead area.

 

My brake pedal feel has recently become a bit vague occasionally.

 

The knocking doesn't happen with slight pressure, but under standard braking it will do it. I was testing the issue earlier and if I brake and it knocks and then brake again - it won't do it the second time. So it's as if something is moving to cause a knock, and then comes back out of place again a little while after when breaking again.

 

As I can practically pinpoint it to the servo area from feel - which components are likely to cause the knock would people say? Is play from the rod behind the pedal to the servo likely to be the culprit perhaps?

[welshpug 1,655]

check the caliper carrier to hub carrier bolt threads are clean, I've had bolts which have torqued up but not actually clamped the carrier!

[chipstick 382 1 Cars]

Noted. I shall check that The calipers were off when I renewed all the suspension bits a couple of hundred miles ago so they may well have worked loose.

[PhilNW 43]

Check the subframe bolts have not worked loose, esp under the footwells. If they have then loctite them back in

[Slo 283 1 Cars]

I had a clonking sound recently when pressing the brake pedal with no brake pipes on my new master cylinder, checked all the mounting nuts and couldn't put my finger on it. So got my old rusty one out and had a look round it and noticed there are 4 nuts that hold the servo to the pedal box hidden behind the soundproofing sponge so checked these on mine and they were all loose. A quick tighten up and no noise at all, just a possibility to check!

[chipstick 382 1 Cars]

Thanks for the replies

 

check the caliper carrier to hub carrier bolt threads are clean, I've had bolts which have torqued up but not actually clamped the carrier!

Bingo! Checked everything over for movement and one of the carrier bolts to the hub was ever so loose. Nipped it up - no more knocks

[welshpug 1,655]

the silliest of little things eh, lucky it hadn't worked further loose!

Edited August 7, 2013 by welshpug

[chipstick 382 1 Cars]

Yeah I was lucky.

 

Now I know that has sorted the issue I will remove the bolts and clean the threads up before I drive it again.