Ln106 Brake knocking noise

[JP106]

Hey guys,

I recently changed the rear wheel cylinders on both sides as well as the brake shoes. I have bled the system 2 times starting from the master cylinder then to rear left etc etc as according to the manual.

Now i have a weird noise that is coming from what seems to be the front of the vehicle. I have power in the brakes ie able to lock them up on a dry newly resurfaced road with 31's.

The noise seems to be a mechanical knocking, when I push the brake pedal in really hard. It's not the brakes as I have listened around the vehicle while someone pushes them in, it seems to be coming from the brake master cylinder or the pedal or thereabouts..

Do I possibly need to adjust something else?

Thanks,
John

[thehanko]

so when you put the brakes on there is a clunk?

could be lots of things - i have seen a brake caliper with a loose or missing bolt go clunk when the brakes were applied.

coming from the master cylinder? that would be weird. is it a single thunk each time or is it a repeating noise like thunk thunk thunk?

does it do it when the brakes are applied in a stationary vehicle? when running and when turned off? or only when running and moving?

[JP106]

it happens when the car is sationary and moving. happens when i push the pedal alllll the way in.. hard and medium.. not when soft. i took apart the rear brakes again today and see if i could see anything that was damaged or moved in the mean time.. couldnt see anything.

bought a brake line clamp and clamped so there is no braking to the back.. brakes a nice and strong and no noise coming from the front..

[Rory]

are ur rear u bolts tight? might be the diff rolling under braking.

[thehanko]

sounds weird mate, but if it happens any time you push the brake hard, then get someone to do it and you follow the sound, something must be loose, a bolt on the booster or something.

good luck

[RaeNTroy]

I have the same problem at the moment with my 80

[trains]

Hey guys,

I recently changed the rear wheel cylinders on both sides as well as the brake shoes. I have bled the system 2 times starting from the master cylinder then to rear left etc etc as according to the manual.

Now i have a weird noise that is coming from what seems to be the front of the vehicle. I have power in the brakes ie able to lock them up on a dry newly resurfaced road with 31's.

The noise seems to be a mechanical knocking, when I push the brake pedal in really hard. It's not the brakes as I have listened around the vehicle while someone pushes them in, it seems to be coming from the brake master cylinder or the pedal or thereabouts..

Do I possibly need to adjust something else?

Thanks,
John

Ok
Inside your brake booster assy , Between the push rod that is moved by the brake pedal, and the pushrod that actuates the master cyld, there is a rubber disc called a reaction disc.

Every now and then, when bleeding brakes, this disc can fall out, and results in a knock, and much more sensitive brakes when brake pressure is applied to the pedal.
In most cars, its downright dangerous, very little between off and sudden full brakes.

Take mcyld off, remove the pushrod carefully, and inspect for the rubber disc, if its missing, get a new one, and problem should be addressed.

Not alot of people are aware of this, but it comes up every now and then.

T

[RaeNTroy]

mine was a missing bolt in the top of the caliper and a loose bolt on the bottom...note to self-CHECK ALL BOLTS!!!

[JP106]

Hi guys,
I have taken everything apart again. Checked bolts twice, even up the front where the master cylinder is etc etc..

I went and bought a hose clamp and I locked out each section of brakes step by step.

It turns out that the noise is coming because of the back brakes.. At first i thought it was a mechanical noise (as i was sitting in the cab pressing the brakes most of the time) but i got my dad to swap places with me and it seems to be more of a air in line/going through a tight hole when under real pressure..

Happens only when i slam the brake pedal in... Doesnt effect the braking of the lux. I am able to lock it up on a dry road.

I took it to a mechanic and they could not be bothered or didnt want to find out exactly what the noise is and they said they couldnt find anything wrong blah blah blah.. didnt pay for it but they just wasted my time.

I still think there is something wrong.. I think i'm going to have to take it to a brake specialist

Any one friends with or know a good brake specialist around the st george region in sydney?????

Thanks for all the replies... This is bugging the sh*t outta me..

john