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Knock in front left after moderate to hard braking 

 

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 Post subject: Knock in front left after moderate to hard braking
Posted: Sun Jun 12, 2011 9:07 pm 
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Hi, I have an au2 that has a knock in the front left.

The pre condition for it is moderate to hard braking. Then when you accelerate it knocks again.

If you brake lightly, it won't knock. You can also accelerate as hard as you like and it won't knock after light braking.

I noticed it also does it when hitting big bumps like a pothole.

I went to my usual mechanic, who put it up on the hoist and said visually everything looked fine.

Car has done 100,000 kms

Thought on what I should try first?
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 Post subject: Re: Knock in front left after moderate to hard braking
Posted: Sun Jun 12, 2011 9:10 pm 
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Ball joints? tie rod ends?

 

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 Post subject: Re: Knock in front left after moderate to hard braking
Posted: Sun Jun 12, 2011 9:12 pm 
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Ride: BA Falcon XT

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Front Hub, Front lower ball joint and then lower control arm bushes and upper control arm bushes. Have all the bolts and nuts been tightened on the front? Are your Calipers ok? does it look like you need new pads?
Have you looked at BOTH side calipers and seen if the wear on the pads is about the same?
Check to see if your Calipers are moving free?

Wouldn't hurt to have ALL of that checked and while you are at it, check the Shocks and springs.
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 Post subject: Re: Knock in front left after moderate to hard braking
Posted: Sun Jun 12, 2011 9:18 pm 
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[flash=][/flash]Thanks for the quick responses!


Mechanic says ball joints are fine.

Cars had new rotors, pads, shocks, shock mounts and d bushes in last 2000kms. It knocked before and after those changes were made. Upper arms done about 20k ago.

I immediately thought lower control arm, but these are expensive so don't want to change for the hell of it. Aparantly the front is hydraulic and whilst they can look ok they can be split.

How do you test things like hubs and lower arms?
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 Post subject: Re: Knock in front left after moderate to hard braking
Posted: Sun Jun 12, 2011 9:26 pm 
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Spinning the Hubs will tell you if there is any wear in the bearings in the hubs, when they are work they will give a kind of grating sound or will have free play when you put load on them.

With the Ball joints, did he TEST them or just a visual? The lower Control arm bushes can be a pain and DO necessitate removal to change. Did anyone check that the guide pins on the Calipers were greased and free moving? some people just change pads and never check things like that.
One other thing, check the sway bar links, they can attribute to a front end knock.
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 Post subject: Re: Knock in front left after moderate to hard braking
Posted: Sun Jun 12, 2011 10:10 pm 
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Papa Smurf wrote:
Spinning the Hubs will tell you if there is any wear in the bearings in the hubs, when they are work they will give a kind of grating sound or will have free play when you put load on them.

With the Ball joints, did he TEST them or just a visual? The lower Control arm bushes can be a pain and DO necessitate removal to change. Did anyone check that the guide pins on the Calipers were greased and free moving? some people just change pads and never check things like that.
One other thing, check the sway bar links, they can attribute to a front end knock.



Yeah he tested them.

Will check bearings and guide pins tomorrow. When you say check sway bar links, is it just that they are tight or is there something else to look for?
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 Post subject: Re: Knock in front left after moderate to hard braking
Posted: Sun Jun 12, 2011 10:40 pm 
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I could bewrong if this will matter but hey the link pins to sway bar are weak as a b**ch C***.

 

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 Post subject: Re: Knock in front left after moderate to hard braking
Posted: Mon Jun 13, 2011 12:36 am 
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Sway Bar link are the double ended ball joint type link that secure the sway bar to the lower control arm. Has this vehicle been involved in hitting the gutter on the left hand side?
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 Post subject: Re: Knock in front left after moderate to hard braking
Posted: Mon Jun 13, 2011 9:34 am 
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Papa Smurf wrote:
Sway Bar link are the double ended ball joint type link that secure the sway bar to the lower control arm. Has this vehicle been involved in hitting the gutter on the left hand side?


It's funny you asked that Papa smurf...I noticed a chunk out of the side wall of the tyre so I would say it's a possibility (it's my wife's car). She couldnt tell me when it may have happened so can't relate it to when the knock started.

Could this be the culprit?
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 Post subject: Re: Knock in front left after moderate to hard braking
Posted: Mon Jun 13, 2011 11:12 am 
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Well, the brackets that hold the sway bar to the body can get damaged very easily and you really have to take a look sometimes to see it, the brackets are easily changed as they are only held on by bolts, either hex head or allen key.

Part number for R/H BA2 5B482 A $31.00 and L/H AU2 5B482 C $32.85.
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 Post subject: Re: Knock in front left after moderate to hard braking
Posted: Mon Jun 13, 2011 1:08 pm 
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Papa Smurf wrote:
Well, the brackets that hold the sway bar to the body can get damaged very easily and you really have to take a look sometimes to see it, the brackets are easily changed as they are only held on by bolts, either hex head or allen key.

Part number for R/H BA2 5B482 A $31.00 and L/H AU2 5B482 C $32.85.



Bearings are ok. Guide pins are lubed.

Brackets look fine, although there Is a slight bend in them on both sides. Should they be dead straight?

thanks for the part numbers.

Last edited by hot_eb on Mon Jun 13, 2011 2:27 pm, edited 3 times in total.

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 Post subject: Re: Knock in front left after moderate to hard braking
Posted: Mon Jun 13, 2011 1:27 pm 
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AU's don't have castor rods like early Falcons do they? i was thinking castor rod bushes. but they changed the lower arm design in AU

 

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 Post subject: Re: Knock in front left after moderate to hard braking
Posted: Mon Jun 13, 2011 2:20 pm 
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WILDEB wrote:
AU's don't have castor rods like early Falcons do they? i was thinking castor rod bushes. but they changed the lower arm design in AU

No castor rods - they have the ba style lower control arm.

I read the front bush is hydraulic and even when worn can still look like new. I am not convinced it is the arm though as it sounds like a high knock, but the fact it happens after moderate to hard braking makes me feel it could be lateral movement in the lower arm.

Was hoping someone else had a similar problem to confirm it for me before I give up a few hundred tokens on remanufactured arms!

Anyone know what the service life of the lower arms is?
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 Post subject: Re: Knock in front left after moderate to hard braking
Posted: Mon Jun 13, 2011 9:03 pm 
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I got 170,000 klms out of my original arms before I changed to the BA lower ones. It might be worthwhile to take it to a suspension place, they have more experience.

Short of that, I can recommend one guy who won't screw you, he is a sponsor on this site and is at Liverpool, Joe from Crescent Motor Sport.
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 Post subject: Re: Knock in front left after moderate to hard braking
Posted: Tue Jun 14, 2011 6:25 pm 
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Papa Smurf wrote:
I got 170,000 klms out of my original arms before I changed to the BA lower ones. It might be worthwhile to take it to a suspension place, they have more experience.

Short of that, I can recommend one guy who won't screw you, he is a sponsor on this site and is at Liverpool, Joe from Crescent Motor Sport.



Thanks Papa Smurf. I took it to pedders - they did a safety check and said lower arms and $1100 to do it.

Out of interest, how did you know your arms needed replacing Papa Smurf?
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