2016 Yaris MOT adviseries

[BobHos]

Hi

At the last MOT I was told the front suspension bushes/pins were worn and the front brake pads were cracking at the edges. The car has only been driven carefully for 21,000 miles. Has anyone else experienced these problems?

[Hornet3D]

54 minutes ago, BobHos said:

Hi

At the last MOT I was told the front suspension bushes/pins were worn and the front brake pads were cracking at the edges. The car has only been driven carefully for 21,000 miles. Has anyone else experienced these problems?

It is not only miles driven that has a bearing of part wear a lot depends on driving style and the types of roads that were driven over not to mention the effect of ageing.  Wear on brake pads at 21,000 seems acceptable although I would not have thought that cracking at the edges was the norm.  I can remember in my motoring history that both pads and brake disks lasted a lot longer but that was in the days of asbestos the change to metal brake pads changed all that.

[Bernard Foy]

1 hour ago, BobHos said:

Hi

At the last MOT I was told the front suspension bushes/pins were worn and the front brake pads were cracking at the edges. The car has only been driven carefully for 21,000 miles. Has anyone else experienced these problems?

A lot of variables can add up to unusual wear and tear, also how the car was driven and how many different drivers. I once had an Opel/Vauxhall Astra which I had bought new. Before it was written off in a car smash, it had done over 80,000 miles and I never had to replace a track rod end or a bushing of any kind or even brake pads. So different driving habits and how the car is driven, what terrain is like, is it near the seaside, plus age can make a huge difference.

[BobHos]

Hi new to this site so I do not know how to reply to individuals but thanks for the 2 replies so far.

I have been a driver for many years and consider myself to be a careful one. The thing that surprises me is that the car has only been used mainly for inner city driving and the MOT was only at 17,000 miles. I wonder if the 2016 Yaris has inherent weakness/problems with the suspension and brakes. I do not think that asking Toyota will help as there has not been any safety alerts or safety recalls. I am  unable to carry out a detailed examination myself (79 years old with severe back problems) and I am reluctant to return it to the Toyota agent where I bought the car (and had MOT done) for examination as I expect they will just say I should replace brake pads and discs plus front suspension parts. 

[FROSTYBALLS]

As the car has only done 21,000 in six years, and the MOT was done at 17,000, presumably the MOT was done a while ago?

[BobHos]

We had 2 cars (my wife and I ) till I sold my car last July. Since then we only drive the Yaris which had its MOT last August.

[BobHos]

I should also add that the brake issue is extremely puzzling as we constantly use the extra regenerative braking feature (labelled "B' on the gear selector console) which greatly helps fuel economy and, I thought, would also save wear on brakes and discs. It is an excellent feature and we use it all the time. Most puzzling???

[Starensis]

You will still use foundation braking system even though putting into B is braking using the hybrid system. In fact, using foundation braking is good, otherwise, you may end up with rusty discs and seized calliper pistons.

[BobHos]

yes it is almost impossible to rely solely on additional regenerative braking, which can only be used for anticipated slowing,  but with its proper use it should extend the lifetime of foundation components.

[TonyHSD]

Hi, 

here I see it’s a hybrid, low miles and few years old.
Toyota hybrids suffer from brake issues but not from been used a lot and the usual wear, actually it’s exactly opposite.
The car slows down mostly with regenerative braking the actual brakes does get very little work and  remain cold and get rusty very easily. Also driving the car in B mode often is wrong and simply add to the issue with the brakes instead of helping it. B mode it is not for general use as regenerative braking add on but only as engine braking while driving continues down hills, also B mode add extra heat to the drive train and extra stress plus does not help with efficiency even quite opposite, it reduces efficiency. For the wear of the brake discs and pads it is indeed too early at that mileage imo except rust other ageing it’s not likely therefore a good mechanic can inspect and if within recommended thickness can salvage them like to clean and lube slider pins and brake fluid change. If the discs and pads are worn out indeed prematurely can be also as a result of stuck callipers and slider pins something often happens in hybrids especially on low mileage cars. I can suggest a visit to another place for second opinion. 
Regards 

[Catlover]

3 hours ago, BobHos said:

I should also add that the brake issue is extremely puzzling as we constantly use the extra regenerative braking feature (labelled "B' on the gear selector console) which greatly helps fuel economy and, I thought, would also save wear on brakes and discs. It is an excellent feature and we use it all the time. Most puzzling???

To add what Tony has said, can I suggest you look into the Yaris manual as to the recommended use of B.  It is not for general use, but for descending steep hills where you would normally get engine braking. When descending steep hills you slip into B mode, depending on the steepness of the descent you may need to apply foot brake as well. As soon as the descent has levelled out then go back to D mode.

[BobHos]

Thanks for your replies and information gentlemen, It is certainly thought provoking. I am not a mechanic but I am an electrical engineer with many years working on electrical and mechanical issues. I did read the manual when I got the car and was aware of the reference in it to use of the "B" selection when descending steep hills. Being an engineer I concluded that the regenerative function would assist the normal braking function and help reduce wear on brake pads and discs. It also improves efficiency and fuel consumption by converting vehicle momentum energy into electrical energy (stored in battery). When we drive the car we still use the foundation braking system quite a lot, certainly enough to keep the brakes functioning properly I would have thought. As I said earlier we can only use the additional ("B" mode) braking for anticipated slowing like approaching busy junctions, traffic lights and long vehicle queues, etc.

[BobHos]

As a foot note I thought I would add that using the "B" mode as I have described I have found that it improved city driving fuel economy by more than 10mpg. I have carefully tested and monitored this for quite some time.

[TonyHSD]

31 minutes ago, BobHos said:

As a foot note I thought I would add that using the "B" mode as I have described I have found that it improved city driving fuel economy by more than 10mpg. I have carefully tested and monitored this for quite some time.

No argument if that works best for you.  For the brakes one idea to look at the wheels if there is any extra brake dust on them (reddish brown colour) and if they get excessively hot you can measure them with infrared thermometer after a drive and they should not be hotter than 40C°. Cracked brake pads happens usually from overheating and this is not typical for hybrids. 

[Catlover]

Well, carry on Robert.  Obviously Toyota, the car maker, have got it all wrong.         
I rarely use B as there are no steep hills where I live, and yet in my Prius I regularly get over 80mpg in the summer, sometimes over 90mpg (92mpg on a 100 mile run, 96mpg on a 50 mile run).

[BobHos]

Thanks for that info. TonyHSD. I will have a closer look tomorrow at the wheels but I think I would have noticed an excessive amount of residue build up. The only infrared thermometer I have is a clinical one but it may be ok for the job. You seem to have a lot of in-depth knowledge/understanding, are you a mechanic?

Any thoughts on the front suspension pins and bushes which seem unusual for a 17,000 MOT inspection?

[BobHos]

Sorry Catlover I missed your latest post. 

Perhaps the only reason Toyota only mention downhill use of "B" mode is to prevent people inadvertently leaving it in "B" mode which certainly would be harmful in normal driving. 

[Red_Corolla]

The B mode isn't a magic switch that increases the regeneration effect, the car already does that to the limit of what the electrical components and Battery can cope with while you are in D.

What B does is actually sacrifice electrical energy to save your brakes on long hill descents. It does this by spinning up the engine without fuel and using the compression as a brake, but spinning the engine over without firing it is obviously wasteful, because the motor-generator is driving it electrically as a compressor. Watch your rev counter (if the car has one) and you will see that it's engine braking giving you the extra deceleration, not the generator. I have a feeling your mind is made up about this and that's fine, but even so I would encourage you to look into it a bit further.

[BobHos]

Thanks for that information Red_Corolla what you say is very interesting and I would never have thought that was how it worked but it sounds very plausible and I will consider and investigate it further tomorrow. I think that when I operate in coasting "B" mode, however, I can see that the power meter and motor/generator/battery screen  indicate power regeneration back into the Battery. This would not happen if the motor/generator(s) are being used to drive the engine ("like a compressor") - need to check tomorrow (hopefully).

 

By the way Catlover think I need to get myself a Prius if that is the sort of average consumption you are getting - phew!

[Bernard Foy]

Bob, as others have advised, I would agree to only use B mode to assist downhill braking. Also have the brakes looked at by another mechanic or garage. In view of the low mileage I would be a little bit wary of MOT advisories. I’m not casting a slur on the motor trade but some do try to generate additional income from unwary customers. However most are trustworthy, and if you get warnings about potential safety related issues then it’s a must have replacement/ repair.

[TonyHSD]

3 hours ago, BobHos said:

Thanks for that info. TonyHSD. I will have a closer look tomorrow at the wheels but I think I would have noticed an excessive amount of residue build up. The only infrared thermometer I have is a clinical one but it may be ok for the job. You seem to have a lot of in-depth knowledge/understanding, are you a mechanic?

Any thoughts on the front suspension pins and bushes which seem unusual for a 17,000 MOT inspection?

Hi, for the suspension bushes any wear at that low mileage is extremely premature however can happen as a result of speed bumps , kerb mounts and salt and grit  from winter drive on motorways., these 3 factors are most common. But again best to seek second opinion. Sometimes also rubber bushes on front suspension arms can look cracked and worn out but been actually fine if there are no cut and no excessive movement. All they may need is cleaning with water/shampoo and then spray some silicone spray on them to rejuvenate the rubber. I am not certified mechanic but look after my cars myself and I like cars and driving, been in the trade previously now just like a hobby 🚗👍 

[Red_Corolla]

12 hours ago, BobHos said:

Thanks for that information Red_Corolla what you say is very interesting and I would never have thought that was how it worked but it sounds very plausible and I will consider and investigate it further tomorrow. I think that when I operate in coasting "B" mode, however, I can see that the power meter and motor/generator/battery screen  indicate power regeneration back into the battery. This would not happen if the motor/generator(s) are being used to drive the engine ("like a compressor") - need to check tomorrow (hopefully).

 

By the way Catlover think I need to get myself a Prius if that is the sort of average consumption you are getting - phew!

Bob,

With respect to the comment I've highlighted, the hybrid transmission has two motor-generator (MGU) units.

MGU1 is connected to the gearbox input. It spins the engine for starting (or for B mode) and works as a traditional generator for charging the Battery from the engine. It also adjusts the drive ratio of the planetary gearbox, so that the engine can contribute to driving the car at the same time. This particular unit cannot recover energy from inertia.

MGU2 is connected to the gearbox output. It drives the wheels using Battery power and charges the Battery from inertia during deceleration. This is the only one that can recover energy from inertia.

So, you see, the system can recover energy and expend it at the same time. That is what B mode does - everything working together to slow the car down as much as it can without applying brakes. MGU2 recovers energy as much as it can and MGU1 sacrifices energy to try and slow down more. It's designed only for very rare scenarios like mountain descents where you want to try and prevent the brakes from overheating.

Obviously, the optimum strategy for economy is not to slow down at all until necessary, which is why normal D mode is better in situations where you need to ease off without stopping - you get a much better coasting effect, but you still have access to the maximum regeneration possible by putting gentle pressure on the brake pedal. The key to good fuel efficiency is always to slow as gently and over as long a distance as possible.

[BobHos]

11 hours ago, BobHos said:

Thanks for that information Red_Corolla what you say is very interesting and I would never have thought that was how it worked but it sounds very plausible and I will consider and investigate it further tomorrow. I think that when I operate in coasting "B" mode, however, I can see that the power meter and motor/generator/battery screen  indicate power regeneration back into the battery. This would not happen if the motor/generator(s) are being used to drive the engine ("like a compressor") - need to check tomorrow (hopefully).

Just tested the car. Travelling along at about 20mph I released the accelerator pedal and switched gear lever to "B" then checked the power meter and motor/generator/battery screen as the car coasted/slowed down. Both showed regeneration from the electric motor/generator to the hybrid battery as I thought and have witnessed before. It appears that the additional braking force in "B" mode arises from the car momentum power being used to drive the electric motor in generator mode to charge the hybrid battery.

I think the description in the owner's manual is misleading when it says that "B position is for engine braking" . I think it means that indirectly the engine (or more accurately all moving parts of the car) transfer their momentum/power to braking power through regeneration. 

 

 

[Red_Corolla]

No, the 'engine braking' description is exactly what it does, but it can still do some regeneration at the same time. See my last post for the full explanation of how it's achieved.

[BobHos]

5 hours ago, Red_Corolla said:

Bob,

With respect to the comment I've highlighted, the hybrid transmission has two motor-generator (MGU) units.

MGU1 is connected to the gearbox input. It spins the engine for starting (or for B mode) and works as a traditional generator for charging the battery from the engine. It also adjusts the drive ratio of the planetary gearbox, so that the engine can contribute to driving the car at the same time.

MGU2 is connected to the gearbox output. It drives the wheels using the battery and charges the battery from inertia during deceleration. This is the only one that can recover energy from inertia.

So, you see, the system can recover energy and expend it at the same time. That is what B mode does - everything working together to slow the car down as much as it can without applying brakes. MGU2 recovers energy as much as it can and MGU1 sacrifices energy to try and slow down more. It's designed only for very rare scenarios like mountain descents where you want to try and prevent the brakes from overheating.

Obviously, the optimum strategy for economy is not to slow down at all until necessary, which is why normal D mode is better in situations where you need to ease off without stopping - you get a much better coasting effect, but you still have access to the maximum regeneration possible by putting gentle pressure on the brake pedal. The key is to slow as gently and over as long a distance as possible.

 

Hi Stuart

Just read your last reply and it tells me a lot more than I originally knew or assumed. Need to think a bit more about it but I daresay you are correct. You seem to know quite a lot about the detailed construction and operation of hybrid systems. Can you recommend any good reading material?

The only thing that puzzles me though is my observations and results in the past for similar journeys with and without using "B" mode as I have described. these test runs appeared to indicate a fuel efficiency improvement of about 10 mpg using my method of using "B" mode. Need to test again.