Rattling rear of Yaris

[Bernard Foy]

Hi guys, I went for a little bit of a drive today after having Covid, the car not being started for eleven days. Started up perfectly and reversed out of driveway unto the road. Into D and away I go nice and slowly, but I felt a loud slap on every turn of the rear wheels. So I stopped and the slapping noise stopped, into D again and as I gained speed the slapping noise increased in relation to the speed increase. So I drove on increasing in speed and within the space of about half a mile the slapping noise disappeared 🤔🤔. Drove on a couple of miles and parked up for an hour, came back the car behaved normally and I drove home. It sounded like something was stuck to a rear wheel and walloped against the body every time that the rear wheels turned, it totally disappeared and I’m left wondering what the heck caused it. The only thing that I can think of is that due to the car being parked up for so long one of the rear pads had somehow stuck to the rear disc and it some time to rattle back to its proper position. Any thoughts from other Toyota owners??.

[TonyHSD]

15 minutes ago, Bernard Foy said:

Hi guys, I went for a little bit of a drive today after having Covid, the car not being started for eleven days. Started up perfectly and reversed out of driveway unto the road. Into D and away I go nice and slowly, but I felt a loud slap on every turn of the rear wheels. So I stopped and the slapping noise stopped, into D again and as I gained speed the slapping noise increased in relation to the speed increase. So I drove on increasing in speed and within the space of about half a mile the slapping noise disappeared 🤔🤔. Drove on a couple of miles and parked up for an hour, came back the car behaved normally and I drove home. It sounded like something was stuck to a rear wheel and walloped against the body every time that the rear wheels turned, it totally disappeared and I’m left wondering what the heck caused it. The only thing that I can think of is that due to the car being parked up for so long one of the rear pads had somehow stuck to the rear disc and it some time to rattle back to its proper position. Any thoughts from other Toyota owners??.

Hi, 

very likely to be from the brakes. You can have look the discs surfaces if they have some traces of rust or any lines on them most likely is a surface rust and a marks from where the pads been holding the discs while parking brake was applied. It will disappear with the time and mileage. You can do some continuing slow downs let say from 50mph down to 20mph in N neutral to accelerate cleaning process but even without few more stops and they will get back to normal. 👍

[Cyker]

Usually if it's brakes it's more of a rhythmic grinding sound.

Maybe there was a Bag for Life stuck to one of the wheels!  

 

[bathtub tom]

Is the car garaged, or parked outside? If the latter, try driving with the handbrake on for a few hundred yards, that should remove any corrosion on the brakes.

[Cyker]

Don't think you can do that on the Mk4...

 

[Roy124]

I'm with Cyker, sounds like something picked up, making a sound at each revolution and more rapidly as you go faster.  Eventually it wore out or it came off.  If it was worn you might find traces. 

[Bernard Foy]

41 minutes ago, Roy124 said:

I'm with Cyker, sounds like something picked up, making a sound at each revolution and more rapidly as you go faster.  Eventually it wore out or it came off.  If it was worn you might find traces. 

No can’t be anything picked up Roy, or it would have manifested a rattling before the car stopped last, before my isolation for Covid. It has be because of being in P for a long period of time. I wondered if any other Owners experienced the same.?? Still less than 600Km on the clock, that may also have a bearing on it.

 

[flash22]

as above surface rust on the rotor, hot days and cold nights, one of the pads hung up, no rust where the pad would have been with the handbrake on leaving a clean spot

grind where the rust was, then slap when it got to the clean part, hybrids are very light on the rear brakes, so it takes a while to get heat in them

[Roy124]

Bernard, I was thinking something like plastic bag while it was laid up. 

Of Covid i hope well on recovery.  I am on day 6 and the car laid up for.  Feel fine since yesterday but get tired very quickly

[Bernard Foy]

12 minutes ago, Roy124 said:

Bernard, I was thinking something like plastic bag while it was laid up. 

Of Covid i hope well on recovery.  I am on day 6 and the car laid up for.  Feel fine since yesterday but get tired very quickly

Roy it was more a clunky sound made by something solid than anything of that nature. Yes I’m over the hump now and have tested negative for two days in succession, but I had a really bad experience. Thankful I didn’t have to go to hospital and recovered at home. Yes it takes its toll on energy levels. My bride of almost 55 years now has it but thankfully symptoms not severe. But still testing positive. Caught it from me of course. Hope you feel better soon 🙏

[TonyHSD]

Hand brake on while driving will cause more trouble than help. I have done that previously and what happens is even worse, best not to do it. Few harder and longer slow downs will clean the discs nicer. Doing handbrake on and driving cause a lots of heat and drag and at the end you smear more pad material onto the disc surface and causing more permanent uneven surface and more issues.,and you also might not be able to as cyker mentioned, you have electronic parking brake aren’t you. Get well soon all.👍

[bathtub tom]

2 hours ago, flash22 said:

hybrids are very light on the rear brakes, so it takes a while to get heat in them

I thought hybrids applied the rear brakes before the fronts.

Braking:

1:  First brake pedal pressure, re-generative.

2: Second brake pedal pressure, rear brakes (because the fronts are already being retarded by re-generation and you need retardation at the back for stability).

3: Further brake pedal pressure applies the front brakes.

Or have I mis-understood it?

[AlJ]

I had the same thing, apart from it sounding like it was from the front wheels, after a lay up for about ten days. It's just brake binding, though I agree it does sound more alarming on the Mk4 Yaris Hybrid than any other car I've had! 
It sounds like something has come loose and is flying around with the wheel and yes, the rhythm increases with the speed. It's nothing to be concerned about and will clear after a short distance's driving. I mentioned it to a couple of people at my Toyota dealership, independently and the answer from both was along the lines of "Yes, they do that if the brakes have been on for a while". 

[Cyker]

50 minutes ago, bathtub tom said:

I thought hybrids applied the rear brakes before the fronts.

Braking:

1:  First brake pedal pressure, re-generative.

2: Second brake pedal pressure, rear brakes (because the fronts are already being retarded by re-generation and you need retardation at the back for stability).

3: Further brake pedal pressure applies the front brakes.

Or have I mis-understood it?

I wouldn't think so; For safety reasons the front brakes are always engaged first AFAIK; Never heard of any car that would engage the rears first (Discounting e.g. faulty brake balance).

I don't think the regen counts towards that as it has no danger of locking the wheels like friction brakes are (Regen resists turning motion, but requires turning motion to work so theoretically the slower the wheel is turning the less regen braking there is; If a wheel locks up there can be no regen braking - In a way it's the ultimate ABS!)

 

[TonyHSD]

20 minutes ago, Cyker said:

I wouldn't think so; For safety reasons the front brakes are always engaged first AFAIK; Never heard of any car that would engage the rears first (Discounting e.g. faulty brake balance).

I don't think the regen counts towards that as it has no danger of locking the wheels like friction brakes are (Regen resists turning motion, but requires turning motion to work so theoretically the slower the wheel is turning the less regen braking there is; If a wheel locks up there can be no regen braking - In a way it's the ultimate ABS!)

 

He is correct 👌and also most if not all Toyota hybrids wear out rear pads and discs first. I had a couple of Priuses from new and that was the case with all of them. My auris has twice full set of brakes changed because was a low mileage school runner before I had it and brakes got rust and needed new but now when I drive it rear once seems are going faster than front one, definitely regenerative braking counts as proper braking and front discs brakes comes to life third unless you slamming the brakes  all the time 😅👍 Also rear brakes are used often with stability control too. 👍

[TonyHSD]

47 minutes ago, AlJ said:

I had the same thing, apart from it sounding like it was from the front wheels, after a lay up for about ten days. It's just brake binding, though I agree it does sound more alarming on the Mk4 Yaris Hybrid than any other car I've had! 
It sounds like something has come loose and is flying around with the wheel and yes, the rhythm increases with the speed. It's nothing to be concerned about and will clear after a short distance's driving. I mentioned it to a couple of people at my Toyota dealership, independently and the answer from both was along the lines of "Yes, they do that if the brakes have been on for a while". 

To prevent that from happening you can disable automatic parking brake and leave the car in P only if parked on level ground. Here you can see on the discs the mark left from the brake pad while car been left with parking brake on. 👍

[Stopeter44]

9 hours ago, bathtub tom said:

I thought hybrids applied the rear brakes before the fronts.

Braking:

1:  First brake pedal pressure, re-generative.

2: Second brake pedal pressure, rear brakes (because the fronts are already being retarded by re-generation and you need retardation at the back for stability).

3: Further brake pedal pressure applies the front brakes

Do you have a source for that ?

[CPN]

11 hours ago, bathtub tom said:

I thought hybrids applied the rear brakes before the fronts.

Braking:

1:  First brake pedal pressure, re-generative.

2: Second brake pedal pressure, rear brakes (because the fronts are already being retarded by re-generation and you need retardation at the back for stability).

3: Further brake pedal pressure applies the front brakes.

Or have I mis-understood it?

I'm pretty sure that it is not quite so simple as that. Using Hybrid Assistant all the time I am driving, I can actually see when regenerative braking is being applied or not and to what degree. It also depends a lot on the speed of the vehicle, loading and a fair few other factors that the ECUs are measuring.

I have quite often approached a set of lights or a roundabout (where I perhaps needed to stop a little more abruptly than normal because of a sudden change in conditions) and the first pedal pressure has not initiated regen braking at all. If I then lift off and re-apply gently (if I have time), regen kicks in and slows me down without having to use the mechanical brakes. It's worth pointing out that the Mk3 responded in a similar way to this too, so I don't think there is much difference to the braking regime versus the Mk4.

Toyota's Hybrids are much cleverer than you think and the only way to see what is going on in real time is by observing what is going on using Hybrid Assistant (which I would thoroughly recommend) on a smartphone whilst driving.

[Hadrian1]

15 hours ago, Cyker said:

Don't think you can do that on the Mk4...

 

That's right, the brake is either on or off.

[flash22]

mk4 - pull the switch up of 5-10 seconds releases the handbrake if you want to leave the car with the brake off

A little of the braking system description

• 1. Electronically Controlled Brake System

     1. Upon receiving signals from the skid control ECU, this system effects hydraulic pressure control at the 4 wheels.

  2. Regenerative Brake Cooperative Control

     1. Controls hydraulic braking in order to recover electrical energy by utilizing the regenerative braking of the hybrid system as much as possible.

  3. Cooperative Control with EPS

     1. Effects cooperative control with the power steering ECU assembly in order to provide steering assist in accordance with the operating conditions of the vehicle.

  4. Anti-lock Brake System (ABS)

     1. The ABS helps prevent the wheels from locking when the brakes are applied firmly or when braking on a slippery surface.

  5. Electronic Brake Force Distribution (EBD)

     1. The EBD control utilizes ABS, realizing proper brake force distribution between the front and rear wheels in accordance with the driving conditions. In addition, during braking while cornering, it also controls the brake forces of the right and left wheels, helping maintain vehicle stability.

  6. Brake Assist (BA)

     1. The primary purpose of brake assist is to provide an auxiliary brake force to assist a driver who cannot generate a large brake force during emergency braking, thus helping draw the vehicle's braking performance.

  7. Traction Control (TRC)

     1. The TRC helps restrain the slippage of the drive wheels if the driver depresses the accelerator pedal excessively when starting off or accelerating on a slippery surface.

  8. Vehicle Stability Control (VSC)

     1. The VSC helps restrain sideways slippage of the vehicle during a strong front wheel skid or strong rear wheel skid, during cornering.

  9. Hill-start Assist Control

     1. When starting uphill, this control maintains the brake hydraulic pressure to the 4 wheels, in order to momentarily prevent the vehicle from descending backward.

  10. Emergency Brake Signal

      1. An emergency brake signal is used. This function automatically flashes the hazard warning lights in 4 Hz cycles during sudden braking, in order to alert vehicles behind and reduce the risk of an accident.

[Cyker]

10 hours ago, TonyHSD said:

He is correct 👌and also most if not all Toyota hybrids wear out rear pads and discs first. I had a couple of Priuses from new and that was the case with all of them. My auris has twice full set of brakes changed because was a low mileage school runner before I had it and brakes got rust and needed new but now when I drive it rear once seems are going faster than front one, definitely regenerative braking counts as proper braking and front discs brakes comes to life third unless you slamming the brakes  all the time 😅👍 Also rear brakes are used often with stability control too. 👍

Interesting! You learn something new every day!

Is that what you've inferred from experience, or is there some sort of official source for that?

It's just a bit of weird choice for them to make, and I might have to change the way I brake if the rears engage first. Reason that the fronts come on first, traditionally, is to reduce the chance of triggering a rear lockup - The idea is if the surface is bad enough, the fronts would start sliding first, which in the worst case would start to cause understeer and is easier to recover from (i.e. just brake less), but would give you early warning.

If the front is regenning I don't think you'd get that early warning, so if the rusty rears engaged next, there is a higher chance the rears will lock up because of the weight transfer to the front from the regen and extra friction from the rust (I already feel the latter with the fronts when I'm gently braking to a stop - When the fronts cut in it's much sharper than it used to be and I have to back-off the brakes; When the car was new the transition between regen and brakes was almost undetectable! Suspect it's because of the rust...)

 

5 minutes ago, Hadrian1 said:

That's right, the brake is either on or off.

Just to clarify, what I meant is I don't think you can drive with the 'handbrake on' to clear rust in the Mk4, as it will disengage it when you apply power. (At least I think it does, now that I think about it I've never tried! I just have it tied to P/not-P because it's so awkward to use manually)

 

[TonyHSD]

1 hour ago, Cyker said:

Interesting! You learn something new every day!

Is that what you've inferred from experience, or is there some sort of official source for that?

It's just a bit of weird choice for them to make, and I might have to change the way I brake if the rears engage first. Reason that the fronts come on first, traditionally, is to reduce the chance of triggering a rear lockup - The idea is if the surface is bad enough, the fronts would start sliding first, which in the worst case would start to cause understeer and is easier to recover from (i.e. just brake less), but would give you early warning.

If the front is regenning I don't think you'd get that early warning, so if the rusty rears engaged next, there is a higher chance the rears will lock up because of the weight transfer to the front from the regen and extra friction from the rust (I already feel the latter with the fronts when I'm gently braking to a stop - When the fronts cut in it's much sharper than it used to be and I have to back-off the brakes; When the car was new the transition between regen and brakes was almost undetectable! Suspect it's because of the rust...)

 

Just to clarify, what I meant is I don't think you can drive with the 'handbrake on' to clear rust in the Mk4, as it will disengage it when you apply power. (At least I think it does, now that I think about it I've never tried! I just have it tied to P/not-P because it's so awkward to use manually)

 

Hi, 

i have not read any official documents how the system works, not available to me, I am talking from my personal experience as owner and driver of these cars plus some experience from maintenance as you know I do the service myself and I have chance to look up closely what is going on under bonnet 🚗🔧⚙️.  I also use this hybrid assistant app which CPN recommended, it’s really cool indeed 👍. That’s true that the car ecu controls the brakes and can send stopping power to each wheels independently and as per the occasion, sometimes goes to the front , sometimes to the rear. Most of the time in normal driving conditions when you apply brakes the car will definitely use its regenerative braking first and then rear axle to distribute the braking force, then front one to complete its stopping process and once under certain speeds only the brake discs works no regenerative braking at all.
Don’t try this yourself: ⛔️⚠️☣️
I have driven the car once for 20+ miles with faulty speed sensor and as a result there were not working abs, anti skid control  and not working regenerative braking, various warning lights on display and the car felt very different and stopping power was hugely reduced!
 I believe only the front axle actually had any stopping capability because front brakes hydraulic circle ⭕️ is directly connected to the brake master cylinder where rear axle it’s entirely electronically operated. I had to push the pedal a lot just to make the car slow down and stop normally. Engine was running most of the time and hybrid Battery was always empty unless you stop and wait the engine to recharge it. 
Back to the brakes now, I might not be 100% correct about that rear brakes engage straight after the regenerative braking in normal driving conditions but I am positive that rear brakes wear out faster than  front brakes and this is what you will have to change first as recommended by the dealer at around after 40-50k miles. , depends on how you drive. 👌👍

[Cyker]

It's good that you do a lot of the maintenance yourself so you can see these things first hand! The fact that you're finding the rears wear down first does suggest more use of the rear brakes, as most normal cars with all-round discs usually have it the other way round, i.e. fairly clean fronts but rusty backs.

One downside of the steel rims is it's nigh impossible for me to see the pad wear or even the state of the discs without taking the wheels off or borrowing an endoscope or something!

[Peter Monaghan]

Hi Bernard sounds very possible to me that you may have had something like a stone stuck in the tyre tread which has now dislodged itself, a large stone can cause quite a loud banging noise, hope this helps!

[exim]

Funny, I had exactly the same thing Friday arriving at my work car park crawling toward the parking space. Intermittent flap or slap sound presumably with each revolution of the wheel. Inspected the wheels as it sounded as if something was stuck, but nothing in sight.

Listening out for the sound this morning arriving in same circumstances, couldn't hear anything this time.