Knocking noise under gentle braking

[guest4015]

Hi,

I have a knocking noise that occurs under gentle braking below around 20mph. The sound is coming from the ns wheel area. A mechanic has checked the suspension and everything looks ok, the torque settings on the lower wishbone have been checked and all the bushes lubricated but the noise is still there. The noise only starts to happen after around 10 to 15 minutes driving so once the car is warm and the brakes/suspension have been in use, the volume of the sound varies and is a rythmic knocking sound. If stopped for more than 5 minutes the noise will again take around the same length of time to be audible.

The car has done 129k, recently had two new front tyres, pads replaced on the front 10k ago and rear pads and discs replaced a few weeks ago due to a stuck caliper. It is also going in today for a new exhaust middle section.

Does anyone know what could be causing this noise as it has been going on for around 4 months now and driving me mad!

Thanks

[olduser1]

I would suspect a CV joint at that mileage, try the vehicle on both locks, then drive in reverse.
Ideally you need the car on garage brake test unit.
A second person to inspect/detect will greatly help.
Let the forum know how you get on.

[chrisc]

A quick look would be to check for damage to the rubber boot around the CV joint near the wheel itself.  With lubrication in place, wear is unusual but if the stuff leaks out, then they are ruined in weeks.  Fortunately cheap to replace

[culzean]

because it happens under braking could it be something to do with ABS ?  the noise on CV joint should be worst when over on full lock and accelerating at low speed.

[Jazz Hands]

your "mechanic" needs a refresher course

I suppose its horses for courses these days, if it cant be plugged into a computer most dont have a clue 

[guest4015]

Hi guys,

Thanks for the replies.

The mechanic in question has been going for years and is very much not into plug and play. Prefers to get underneath and actually look plus won't charge if he can't find an issue (had the car three hours looking at the suspension and lubricating the bushes etc for nothing).

CV joint is fine, no noise at any other time including driving at full lock or in reverse plus no sign of leakage. First thought i had was the droplinks or else a warped disc.

[Jazz Hands]

sorry if it seems like I'm having a go [and I guess I am out of the apparent lack of skills these days and the security of the interent ],

but come on, surely a mechanic should be able to diagnose this issue, there can't be that many component parts to go through.

firstly you need to be able to replicate the noise in the presence of your chosen mechanic, then you need to find someone with some rollers to get car up to temp and dig around with a stethoscope to home in on the offending area

otherwise your gonna have to get lucky in here with someone who has had a similar problem.

you checked the obvious things like a distorted dust shield around the disc, stone jammed in the caliper, sticking caliper again ?

a cheap investigative where your mechanic could check all the calipers, pistons and followers are free and properly located shouldn't cost the earth and rule out some more items.

[culzean]

i had a warped front disc once and it was way more than a gentle knocking - even the slightest out of true and it is as though someone is shaking the steering wheel when you brake. And it gets worse as you apply the brakes harder too,  and it happened straight from cold as well, didn't have to wait for it to warm up.  If you think it is a warped disc ask your mechanic to swop front discs side to side - brakes may not be the best if you do that because the pads bed into the disc and you will have different pads on the disc surface now,  but a short (careful) drive may tell you if the noise has moved over with the disc, (if the disc is warped you should feel a pull or judder on the steering as well as judder feeding back through the brake pedal).

[madasafish]

It would appear to likely be a brake component which is stuck.. hence the noise when warm.. and rotating. Most likely a rusty brake slide.

Wheels off, pads out, check for corrosion, copperslip all slides and replace. Probably all 4 wheels but start with front nearside where the noise is.  I have had similar problems on my 10 year old Yaris..and it is normal on cars >3 years old: usually starts in winter with salt corrosion.

[guest4114]

hi there

did you get to the bottom of this problem? i have excatllly the same problem it started about 4 weeks ago after i had the tyres changed, my car has been into 2 garages and they cant find anything wrong, spent over 3 hours stripping it all done and lubracting, couldnt find a problem and its still doing it.

[guest4114]

the above is on a 55 plate 1.4 auto car has done 63k if anyone has any ideas would love to know thanks

[guest4015]

Hi all,

Sorry for not posting on this for a while, still not got to the bottom of it as haven't had the time to get it back into the garage. Noise is still coming and going, coincidentally happened shortly after changing the front tyres on mine as well.

Now developing a squeak in the clutch when its depressed audible from outside but not inside so something else to look into as well.

[guest4015]

Well have just changed the front brake discs and pads today and seems fine. Rear caliper is sticking though so gone through a set of rear pads in six months

The clutch just needed lubricated so easy fix.