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Gen 2 brake questions.


Chippy01
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A friend of mine has a Gen II Prius T-Spirit with about 110,000 miles up, and he's worried about the brakes saying he can hear a noise from them.
He's not mechanically minded, so he's asked me to have a look at them.
Since I started driving Prii in 2010 with a Gen II, and now have a Gen III; and my other half has a Gen II now, I have learnt a bit about them - but not too much about the brakes.
For the past few hours I've been searching online and watching YouTube videos, and feel confident enough to tackle them - I think. I just need a couple of pointers, so onto the questions :-

1. After my searches, I have come to the conclusion that the Gen III needs an OBD scanner (which I do not have) to do the brakes properly, but the Gen II doesn't. Is this correct?
2. Do I have to disconnect the 12v Battery on the Gen II to do the brakes? Some reports say you do, some say you don't. 
3. What is the minimum thickness for a worn front disc?
4. What is the minimum thickness for a worn rear disc?
5. Is there anything I should be aware of before proceeding?

This will be just a quick dismantle to ascertain the condition of his brakes, which doesn't bother me on a 'standard' braking system, but with the hybrid regen system, I don't want any surprises.

Thanks.

 

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One thing to remember when working on the brakes, is keep the keys well away from the car. The brake system pressurises as you come near the car with the keys, so when you try to remove the pads or push the piston back, the system will go into over pressure and give a fault code....this will need to be cleared, disconnecting the Battery at this point is not enough.

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IIRC, the Gen 2 without smart key does not pressurise the brakes until you put the key in the slot. No need for an OBD scanner as long as you disconnect the 12v Battery before starting work on the brakes and pump the brake pedal back up to pressure, after you've finished, before reconnecting the 12v.

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On a Gen 2, the brake system is live even when the key is not in the ignition slot. The brake system pump can activate anytime it notices a drop in pressure, after a short delay on opening the driver's door, or if you press the brake pedal.

Bleeding brakes requires a Toyota Intelligent tester or equivalent scan tool and the removal of 2 brake relays when prompted by the Intelligent tester.

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Thanks for the replies, guys.

My buddy called me to say he will be down to me around 11 today.

Even though I am just checking things out, I may have to lift off a caliper just to be doubly sure of something.
When he arrives, I'll get his key and put it into the far end of the house and not open any doors of the car while working on it. The car will not be locked and alarmed, just shut down and open. I'll probably leave the car stand idle for 10 minutes or so before starting jacking it up.

 

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2 hours ago, Chippy01 said:

I may have to lift off a caliper just to be doubly sure of something.

If you do this and do not have a scan tool to reset any DTCs you might trip, you need to remove the 12 V power before removing the calliper. otherwise, with pushing the calliper piston back you could get C1341, C1342, C1343 or C1344 DTCs. These cannot be reset by disconnecting the 12 V after the fact, only by clearing with a scan tool. If you have a scan tool, you can just remove the ABS1 and ABS2 relays which disable the ABS accumulator pump.

If you removed the 12 V and you also pushed back the calliper pistons, make sure you pump the brakes several times to ensure the pistons are pressing firmly against the pads, before reconnecting the 12 V Battery.

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Well, that went well.

After he arrived I shut the car down and removed the key to the far side of the house to be on the safe side.
Removed the wheel brace and the locking nut key from the boot and just closed all the doors, telling him not to open anything.

Then, again to be on the safe side, waited about five minutes before proceeding.

Jacked up one corner at a time, removed the road wheel and lifted the caliper just to get a proper look at the pads. I have a C type micrometer which I measured the discs with, and they are all above minimum thickness, although they are showing signs of corrosion and scoring.
It appears that the original owner had quite recently replaced the original pads with aftermarket ones, as the ones fitted now do not have any Toyota markings on them - OEM pads do.
The aftermarket pads, fitted to already worn and partially corroded edged discs, are either causing the scoring or getting scored by the ridges and grooves that were made from the previous pads. Either way, they are still very meaty and are serviceable/usable for the time being.

After putting everything back together (had to move each caliper piston back about 1mm to get the caliper back on over the pads and discs), I pumped the brakes from the passenger side to reseat everything. 
Then I collected the key, started her up (no warning lights on the dash) and went for a spin. Tested for slow, medium and hard emergency stopping, and everything worked as it should. No squealing, grinding or pulling to either side.

He has about 7,000 miles to go before his next service, and advised that he should change pads and discs all round at the next service. That gives him about 6 months to save up a few shillings for the job - and to be honest, it's what I would do also if it was my car.

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Why change them at the next service ?

7000 miles is nothing for Prius pads, if they're working ok now, they'll still be ok in 7000 miles and more. I'd just inspect again at the next service, I don't think you'll see much difference. If the noise was a groaning sound when going slowly, it'll probably have gone now the pads have been disurbed, SWMBO had it on hers and I basically did the same as what you did above with the addition of a good scrape, clean and coppa slip the backs of the pads and the grooves they sit in and it went away. 

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True kithmo, 7,000 miles is nothing on the brakes of a Prius, but the discs are badly scored and are showing corrosion around the edges, about 1/3 the way in on the discs.
Also the front discs are about 1/2 mm from minimum thickness. I also know that it could take a while to use that last 1/2 mm.
Although the pads look fairly new and have plenty of pad material on them, the scoring and corrosion areas will eventually win and eat them away, even with the Prii's low friction brake usage.
He's intending to keep this car for quite a while, and as I told him - if it were my car, I would change them at the next service.

He was with me watching and looking at the pads and discs himself as I exposed them, so he is in no illusion of their condition.

On a side note, I found out today that he had taken his car to a mechanic friend of his, who told him that his brakes were totally shot and he shouldn't be driving it. Yes, he lifted the car, but made his assumption by just shining a torch behind the road wheel.
In my opinion you can't make that assumption without at least taking the wheel off and having a proper look.

In hindsight, I should have taken a few pics, but alas .................

 

Btw, how do you put your fuelly results at the bottom of your posts?

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12 hours ago, Chippy01 said:

Btw, how do you put your fuelly results at the bottom of your posts?

Visit fuelly to get the 'code' for your fuelly results.

Copy and paste the code into your forum signature.

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13 hours ago, Chippy01 said:

True kithmo, 7,000 miles is nothing on the brakes of a Prius, but the discs are badly scored and are showing corrosion around the edges, about 1/3 the way in on the discs.
Also the front discs are about 1/2 mm from minimum thickness. I also know that it could take a while to use that last 1/2 mm.
Although the pads look fairly new and have plenty of pad material on them, the scoring and corrosion areas will eventually win and eat them away, even with the Prii's low friction brake usage.
He's intending to keep this car for quite a while, and as I told him - if it were my car, I would change them at the next service.

He was with me watching and looking at the pads and discs himself as I exposed them, so he is in no illusion of their condition.

On a side note, I found out today that he had taken his car to a mechanic friend of his, who told him that his brakes were totally shot and he shouldn't be driving it. Yes, he lifted the car, but made his assumption by just shining a torch behind the road wheel.
In my opinion you can't make that assumption without at least taking the wheel off and having a proper look.

In hindsight, I should have taken a few pics, but alas .................

 

Btw, how do you put your fuelly results at the bottom of your posts?

Ah, I see, from your previous description I though you meant the discs were shiny with grooves in and corrosion on the lip, but rust covering 1/3 of the braking surface will need the discs (and pads) replacing, I would say sooner than later TBH.

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3 hours ago, kithmo said:

Ah, I see, from your previous description I though you meant the discs were shiny with grooves in and corrosion on the lip, but rust covering 1/3 of the braking surface will need the discs (and pads) replacing, I would say sooner than later TBH.

I went back and re-read my description. I must admit it wasn't the best. Pics would have said more.
I know my bud is a bit strapped for cash at the moment, so my advice to carry on to the next service was two-fold. First off, despite their poor looking condition they still brake strong with no noises or pulling; and secondly he can start saving.
And I would do the same, carry on and change at the next service. The pads would probably be nearing changing thickness by then anyway.

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