uHu
Bridgeburner
Higher voltage motors have carbon brushes. 12 volt motors have brass or high-copper-content brushes, which do make this kinda dust.
Another ABS Brake Failure
- Thread starter tdkhelene
- Start date
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I've seen and worked with lots of carbon and graphite brushes in 12v applications. I've always understood that the selection of a particular brush material or compound was based more so on current density and contact speed and not voltage - but I may well be lacking in knowledge here. The brushes used in this pump motor application may well be something other than a carbon/graphite compound, I haven't examined them. Can we agree the commutator is F'ed? 
- Thread starter
- #63
So... I believe the vehicle was originally from AZ. It's been up here for about 10 of its years though.
No... no signs of leaking from the tank fittings either...
And yes... the Commutator is F'ed.
Any thoughts on the haze found on the valve block?
No... no signs of leaking from the tank fittings either...
And yes... the Commutator is F'ed.
Any thoughts on the haze found on the valve block?
So... I believe the vehicle was originally from AZ. It's been up here for about 10 of its years though.
No... no signs of leaking from the tank fittings either...
And yes... the Commutator is F'ed.
Any thoughts on the haze found on the valve block?
Soooo, is this a motor that can be rebuilt, or is it trash. Since replacing the motor is a major expense versus the rebuilt ($900 vs. $300), this question is important. If it is not truly rebuild-able, replacing the whole $2000 unit is probably the way to go. But if it is rebuild-able, and reliable then for another 150,000 miles or so, then doing the MC piston replacement, accumulator replacement, and motor rebuild is an increasingly good option.
Gil
Ventura
I was asking is there a way to test our MC ABS motors that are scared of this failure!
As for the corrosion. If no leakage and noticeable outside element exposure maybe it's just the motor life span that is causing all this? It's just odd that some have experienced. It while others with more time (years of vehicle in service) mileage etc have not
As for the corrosion. If no leakage and noticeable outside element exposure maybe it's just the motor life span that is causing all this? It's just odd that some have experienced. It while others with more time (years of vehicle in service) mileage etc have not
- Thread starter
- #67
In this case, it appears as though the armature / commutator is likely rebuildable... I'm going to try and clean it up and test it myself later on this week... I'll let you know what I come up with.
- Thread starter
- #68
Took apart the electric motor the other day... Yikes!
No... those are not flower petals... They are pieces of the commutator...
After counting... only 3 of the 12 pieces of the commutator contacts were left. All others had fallen off. The remaining pieces really looked scored.
Ironically... I cleaned the motor up, put it back together and applied 12V to the contacts... and the motor spun freely. Not sure what it would do under load... but the motor was still functioning.
It looks like there might be a space here where water intrusion may have happened. Hard to say but it's a hypothesis.
No... those are not flower petals... They are pieces of the commutator...
After counting... only 3 of the 12 pieces of the commutator contacts were left. All others had fallen off. The remaining pieces really looked scored.
Ironically... I cleaned the motor up, put it back together and applied 12V to the contacts... and the motor spun freely. Not sure what it would do under load... but the motor was still functioning.
It looks like there might be a space here where water intrusion may have happened. Hard to say but it's a hypothesis.
I have had more than a few cars in my lifetime, but don't recall any ANY that had a design where the brakes would fail to ZERO upon the failure of an auxiliary electric motor that boosts pressure. Seems a pretty poor design, and a terrible fail-safe option! just sayin' - glad we were not hurt when ours failed....since we live 8+ miles up a steep and twisty road!! yikes.
So what are the symptoms? I have a 2000 LX470. Yesterday a truck pulled out in front of me without looking I had to hit the brakes hard. Pedal almost went to the floor. If I pump the pedal it's fine. Was planning to take it in to Lexus this week. Am I looking at the same thing?
Pedal to the floor is one symptom. Take a look at the numerous posts on this problem. Others have had a warning buzzer and the pedal doesn't pump back up if the booster fails completely. You may be looking at a brake master cylinder going bad. By all means, have the dealer take a look. If the master cylinder AND booster pump need replacing at a Lexus dealer, take some smelling salts to revive yourself after hearing the cost.
Pedal to the floor may just mean you need to adjust the push rod on the master cylinder. Especially since you said it's good when you pump the brakes a couple times. I dealt with a soft pedal for a while and finally found this adjustment in the service manual (see my posts on the link below). Make sure to pull all directions from the FSM to ensure proper adjustment.
Source for rebuilt booster pump on master cylinder
In my opinion the master cylinder either leaks or it doesn't. If it doesn't leak it's good.
tdkhelene,
Any luck rebuilding the motor? Were you able to source parts for the commutator? I have an old motor laying around and would love to rebuild it and pass it on to a fellow mudder.
One of my friends is a master tech at our local Toyota dealership - he's been collecting these (they use the same part in the Tundra, Sequoia, and a few others - same failure over time) and he's trying to find a shop that can rebuild these motors. Would save a ton of cash if it could be done...
uHu
Bridgeburner
When the booster fails, you still have a bit of braking power, just that you have to push really, really hard. The effort required is so big that most people think that the brakes are gone. Anyhow, the effect is the same, you can get into a really bad situation when the booster fails, and as someone says here: it will fail sooner or later. Make sure your e-brake is working well. When the booster fails, you have front brakes only, so e-brake on the rears will help.
Pro-active service is important for the booster - it looks like 200 k miles (300 k km) is the limit for how long we can trust the booster. Shorter if you want to be on the safe side.
Having to pump the pedal to get good brakes, is not a booster failure.
When the audible alarm goes off, you have one chance to stop, with full braking power. Make sure you use it right. I see a problem now that I have a new sound system - I will never hear the alarm...
I have a pretty steep hill near my home. Downhill speeds without brakes are usually around 40-50 mph. Most of the time when I'm coming down the hill I think about this issue. So I practice slowing the vehicle by downshifting. If there are no cars behind me I get to third by turning off my overdrive. Drop it to second and finally to L low. I've noticed if I'm still over 30 mph it won't slow me down. Once below 30 or so mph the engine braking power slows the vehicle down to very controllable handling speeds. I guess if I were to have the alarm go on and I had that one chance to stop I would hope for it to get me to stop, but if not the above steps in a very quick sequence would eventually work. Of course the emergency brake would be applied as well. I know when we did the poll on this issue I wondered if there was a corollation between trucks with failure and from particular parts of the states.
Do you lose all brakes or just some efficiency, I can't believe this wouldn't be recalled if you could lose brakes over a simple motor assembly issue. I have brakes without the ignition on and pump running its just a low pedal but they still operate, I tried it earlier, I rolled down a hill no ignition on, the pedal nearly hit the floor but they still operated.
uHu
Bridgeburner
You loose quite a bit more than "just some efficiency", but not all. Braking when the booster is empty is scary. By pressing hard, you get some effect, but not enough in an emergency situation.
And, using the gears, there is no need to move stepwise down through the gears. Just slam it straight into 2 or L, it will not downshift until the speed is right for that gear. It will not change to a gear which would give a too high rpm for the engine, but it will shift down as soon as it is "permissible".
So, we need to practise:
1 - try to break the seatback by pushing the brake pedal
2 - try to break the e-brake lever by pulling it hard
3 - slam the gearshifter as far back as you have time to
And, using the gears, there is no need to move stepwise down through the gears. Just slam it straight into 2 or L, it will not downshift until the speed is right for that gear. It will not change to a gear which would give a too high rpm for the engine, but it will shift down as soon as it is "permissible".
So, we need to practise:
1 - try to break the seatback by pushing the brake pedal
2 - try to break the e-brake lever by pulling it hard
3 - slam the gearshifter as far back as you have time to
