Yaris 2003 - Breaks noise

[BartSimpson]

Hello everybody,

My Yaris (2003 TS sport, 1.5 petrol) has a strange problem. There was a knocking noise coming from the rear during light/smooth breaking. It was diagnosed as crooked discs, so the mechanic replaced the rear discs and pads.
A few days after the replacement a similar knocking noise came from the rear of the car, but this time during normal driving. When gently pressed the break pedal, the issue dissapeared.
The mechanic replaced 'springs' (I assume the springs holding the pads). The problem remained.
Then the mechanic replaced the set of discs and pads again. It was fine for 1-2 days. Eventually the knocking during driving appeared again.

Alternative garage could not diagnose the issue. Please let me know what you think it could be.

 

[Notoyboy]

With such a noise as that, which I assume is related to road speed, something is not right, and to my mind something sounds to be catching.  Odd no-one has found the problem.  Not sure I'd want to drive the car far without identifying the problem. 

Does the handbrake operate on the front or rear wheels?  My Corolla had the handbrake on the drum part of the rear discs (if you see what I mean).  Any work done on the car recently?  Are the wheel bearings OK?

[BartSimpson]

Yes, the noise frequency depends on the speed only. Driving on a gear or idling does not change anything - the noise is still present.
The manual handbrake does not affect the noise (this is a drum part of rear discs, as you mentioned) - when driving and slowly pulling the handbrake, the noise is still there (while when using normal brake, it disappears).
 

[Notoyboy]

Hmmmm....listening to the video again, reminds me of a practical joke someone played one mischief night, slackening the wheel nuts.

You've not said if any work has been done on the car recently.

Not sure if applying the brakes is a coincidence.  Sounds can travel around the car body - have you checked nothing untoward with the front end?  Is the noise worse when turning a sharp bend? 

Try jacking the car up yourself, and spinning each wheel, 1 at a time.  You might not hear the knocking, with the wheel rotating so slowly, but try keeping your hand on the wheel to see if you can feel/pick up a definite "hit"

Takes a little nerve to try it, but I have in the past jacked a car up, and put it into gear with engine running, to check/spin the driving wheels.  Car well supported and chocked of course!

Can't believe the garages haven't found it.  Maybe if you said it was a brakes issue, they didn't look any further?

[flash22]

If the sound changes with speed its usually rotational

Have you had the wheels balanced ? i assume the bearings have been checked

what condition are the handbrake shoes in ?

[BartSimpson]

No other work was done than changing the rear tires when the pads and discs were replaced. The tires were balanced.
The mechanic mentioned all wheel nuts in rear tire (don't remember which side) were loosened (strange!). I did not do anything with the rear tires for years. Now I regularly (nearly obsessively) check the nuts and they do not get loose.

The noise is audible straight after starting rolling. The faster I drive the less distinct it gets. The noise gets worse when turning a sharp right bend.
I will try to roll the wheels with the car jacked, but I did it after the first discs/pads replacement when the noise started and found nothing strange.

The original garage assessed themselves it must be something with the breaks. After such a saga I started thinking that it may be something else (wishbone, bushes), but an alternative garage said it MUST be breaks... They suggested trying again with the original garage before I bring my car to them.

To me it does not sound like bearings. I do not know the handbrake shoes' condition - when the original garage changed the discs, they mentioned the handbrake compounds are fine.

 

[flash22]

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[flash22]

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[Notoyboy]

2 hours ago, BartSimpson said:

The mechanic mentioned all wheel nuts in rear tire (don't remember which side) were loosened (strange!).

Not sure I understand what the mechanic was saying.  I'm presently trying to keep an open mind as to the problem/cause.

I wasn't suggesting wheel bearings could make that noise, but I'm wondering if a worn bearing could cause something to not run true, although I'd have expected the garage/mechanic to have picked up a worn bearing.  Interesting it's worse on a sharp right hander, meaning that an increased load on a particular wheel is making the problem worse.

The wheels: are they originals or has someone changed them in the past?   I assume it's got wheel nuts (rather than bolts).  Could one of the studs in a hub have been damaged during the tyres being changed, and someone has bodged the repair.

Another possibility, though I can't see it making so much noise, but I once had a regular scraping noise develop on a Citroen, which turned out to be a front brake disc catching on the brakes dust shield.  i assume it started once the wheel bearing had some minor (imperceptible) wear. A little bending of the dust shield fixed it!

You'll get there in the end - hope we are helping!

Edited September 9, 2020 by Notoyboy
extra paragraph added

[Bernard Foy]

This comment may be of no help or related to your knocking sound. I had a vauxhall 01astra. Which sounded exactly like the one that you have, turned out it was a fault in the gearbox. Got a second hand box installed, end of speed related knocking sound

[Madasafish]

Check the rear springs have not broken. jack up each side and look carefully at the ends of each spring. Will give odd sounds (been there)

[flash22]

The sound is rotational like shoe in a washing machine the sound could be travelling from the front end

Sounds like the pads are loose and are not being held by the clips

replace the pad hardware and make sure the caliper bracket is free and clear of debris

i would get the rear brakes tested by a MOT place to rule out any imbalance (roller or a skid pad) that should rule out a stuck caliper or blocked/crushed line, also to see if the handbrake shoes are doing their job

[stantheman1]

If you've still not found the cause try looking to see if the holes for the wheel nuts are still round and not out of true, also make sure the wheel nuts are flanged and not tapered and while the wheels are off have a tug at the threaded studs to see if there's any movement.

Good luck, please report back with your findings.