First and foremost: Brakes should only be worked by those with high level of mechanical abilities and experienced with brake systems.
My hope is below link will give better understanding as to what we can do to reduce brake failure and what to watch for. The info is from my experiences and my thinking as to what and why brakes fail on 100 and 200 series. As such, is subject to change, as I learn and others contribute!
IMHO most brake failures are preventable, in the relative shorter term.
It's difficult to define short term. As brake usage in a perfectly health brake system, is so varied. As some are constantly on brake pedal ever few feet (stop and go traffic). Whereas others may go ~200 or more miles without touching pedal on regular basis (HWY vehicle). The 1 million mile Toyota had no brake issues reported IIRC.
It is sudden zero pressure in brake master and lines, that yields pedal to the floor, which results in relatively no usable brakes. This happens from lose of fluid or brake booster pump motor failure.
Eventually all brake booster motor will fail in all motorized brake systems. It's the motor failing to start/run that yields zero pedal more than anything else I've seen. As the motor turns the pump, pressurizing the accumulator.
A few tips:
First:
Never ignore brake warning lights or alarms.
Second:
After vehicle has sat with IG key off, for a few hours. The pressure in brake system bleeds down. The older the system the faster it bleeds down, primarily do to aging of a rubber seal or seals and depletion of nitrogen gas from accumulator. By turning the IG key to ON, the booster motor will activate once pressure sensors senses pressure below a preset level.
By listening before starting engine, brake booster motor can be heard running. Motor not running or run for more than 40 seconds or is a warning. If not heard, press brake pedal a few times, it should than be heard, since pressing brake pedal depletes stored pressure from accumulator. If motor takes all of 40 second run time before stopping most times, or even just when vehicle key off (no power to motor) for short periods, that should be investigated.
Third:
Periodically test booster motor run time. Do this by pumping brake pedal 40 times with IG key off or key out of IG. Than check level in brake master fluid reservoir. Which should be at or near max line but not over. Than turn IG key to ON, and time booster motor run time. 40 seconds is max. 28 second is a very health system (new or newer). 40 seconds is limit, but may indicate some weakness. i.e low voltage/amp from battery, weak seals, bad fluid, etc. Over 40 second, service is necessary.
Prevent measures.
Brake failure:
Brake booster motor failure, is number one reason for no brakes!
I'll start with the most common cause of brake failure. Loss of brake system booster pressure.
Other than no brake fluid in system, which one can easily see. Brake booster motor failure, is number one reason for no brakes.
These are just my opinions I drew from working on 100 series brake systems. Many, muds members help me gain understanding on the subject. Some with their posting in mus, others by sending their failed master to me, to dissect. Thanks all of you
Overfilling brake fluid reservoir, "may" cause loss of brakes:
IMHO this is number one reason for sudden brake failure.
Over filling; Such a small thing, most Toyota Master ASE certified mechanics, will say makes no difference. Most are not even aware; Toyota embossed instruction on topping on the brake reservoir. Even spillage on reservoir can have same effect.
If brake fluid aloud to run down side of reservoir. Fluid may get on the wires and/or into its sheathing. Fluid may then travels down the wire(s) into the boots.
Brake fluid is hygroscopic (pulls moisture from the air). If brake fluid gets in the boots of the brake control wires, which are resistance wires. The wire terminals, nuts & screws will corrode from moisture in fluid. This corrosion will increase resistance of wires, causing the commutator to prematurely wear out. IMHO: This is leading cause of motor failure.
Overfilled brake reservoir or fluid spillage, effect on wires, seen below.
A second cause for brake booster motor failure. Is excessive long run times:
Motor running excessively long, each time it is called (pressure in system low) on to run. This happens most often due to a leak or air in system. Leak is not always external (internal pressure leak). Internal pressure leak, will not cause fluid level to drop. Note: level drops naturally with pad wear. I'll touch on this subject later. But if we hear the screeching sound when motors is running and may see bubbles (wake in fluid seen) come up front of reservoir. This is internal pressure lose. The master will need replacing, or pump will run excessively long. Pump is designed for short run time. Running to long each cycle, can overheat the motor. This (heat) too cause premature wear of motor.
A third cause for motor failure.
Brake fluid, gets in the motor from passive seal in the pump, which is not a pressure seal. It's the seal seen when motor pulled off the pump.
What happens is the motor air vent become clogged. The pump has weep drain canal on face of pump, where motor mounts to it. The pump also has a air vent with boot cover next to the drain canal The motor's mounting face plate, has an air vent hole leading to this air vent boot. This air vent is designed to reduce the vacuum (negative air pressure), built up inside motor, as it spins at high RPM. If the air vent gets clogged, brake fluid is then sucked from passive seal weep area of pump, into motor. If weep canal drain is also clogged, it suck brake fluid out past passive seal from the pump. The brake fluid then soaks/damages the rubber insulation in the motor. This brake fluid can also damage motor bearings. It "may" also affect resistance within motor, by affecting contact between brushed and commutator and or windings IDK.
Pump and motor with clogged vent pictures:
Pump (side motor attaches to)
Motor
Motor & Pump
My hope is below link will give better understanding as to what we can do to reduce brake failure and what to watch for. The info is from my experiences and my thinking as to what and why brakes fail on 100 and 200 series. As such, is subject to change, as I learn and others contribute!
IMHO most brake failures are preventable, in the relative shorter term.
It's difficult to define short term. As brake usage in a perfectly health brake system, is so varied. As some are constantly on brake pedal ever few feet (stop and go traffic). Whereas others may go ~200 or more miles without touching pedal on regular basis (HWY vehicle). The 1 million mile Toyota had no brake issues reported IIRC.
It is sudden zero pressure in brake master and lines, that yields pedal to the floor, which results in relatively no usable brakes. This happens from lose of fluid or brake booster pump motor failure.
Eventually all brake booster motor will fail in all motorized brake systems. It's the motor failing to start/run that yields zero pedal more than anything else I've seen. As the motor turns the pump, pressurizing the accumulator.
A few tips:
First:
Never ignore brake warning lights or alarms.
Second:
After vehicle has sat with IG key off, for a few hours. The pressure in brake system bleeds down. The older the system the faster it bleeds down, primarily do to aging of a rubber seal or seals and depletion of nitrogen gas from accumulator. By turning the IG key to ON, the booster motor will activate once pressure sensors senses pressure below a preset level.
By listening before starting engine, brake booster motor can be heard running. Motor not running or run for more than 40 seconds or is a warning. If not heard, press brake pedal a few times, it should than be heard, since pressing brake pedal depletes stored pressure from accumulator. If motor takes all of 40 second run time before stopping most times, or even just when vehicle key off (no power to motor) for short periods, that should be investigated.
Third:
Periodically test booster motor run time. Do this by pumping brake pedal 40 times with IG key off or key out of IG. Than check level in brake master fluid reservoir. Which should be at or near max line but not over. Than turn IG key to ON, and time booster motor run time. 40 seconds is max. 28 second is a very health system (new or newer). 40 seconds is limit, but may indicate some weakness. i.e low voltage/amp from battery, weak seals, bad fluid, etc. Over 40 second, service is necessary.
Prevent measures.
- Flush brake fluid often. No longer time period between flushes than 3 years, after first factory fluid flushed out.
- I've gone back to using only Toyota brake fluid. It's pricey and may not make any difference. Toyota no-longer states on bottle who makes. But the extra cost worth it for piece of mind. Toyota stated on the bottle "engineered to Toyota spec", may help protect seals in system. Condition of seal is very important to heath. of master. Bad seals can weep or even squeal under high pressure. Booster motor will then run excessively, as pressure keeps dropping.
- Inspect motor run time and listen for excessive running of motor.
- Never overfill brake fluid reservoir. Fluid may escape from cap or grommets at bottom. If fluid get on booster motor brake control wires, it may enter boots protecting wires at connection points under boots. The ensuing corrosion from hygroscopic action, will increase resistance of brake control wires. This will hasten motors failure, very rapidly. Brake fluid may also get into breather port for motor. The moisture will attack dust. This may clog breather and then as motor creates a vacuum (high RPM spin) it will suck fluid from pump into motor.
- Inspect breather at bottom of booster motor annually. Deep water crossings, driving in tall grasses, muck, very dusty condition, missing fender or undercarriage shielding, lifted increasing opening area in fender to engine bay, oversize tires, etc. May all add to debris entering engine compartment. Be on the watch and check breather more often under these or extreme driving condition. Or ensuing fluid sucked into motor from pump, will damage brake booster motor.
- Keep battery, battery post clamps and cables properly serviced. Volt/Amp drop from battery, will be the same as increased resistance in wires. This will also effects RPM (slowing) motor.
- Keep grounds to frame, body and engine properly serviced.
Brake failure:
Brake booster motor failure, is number one reason for no brakes!
I'll start with the most common cause of brake failure. Loss of brake system booster pressure.
Other than no brake fluid in system, which one can easily see. Brake booster motor failure, is number one reason for no brakes.
These are just my opinions I drew from working on 100 series brake systems. Many, muds members help me gain understanding on the subject. Some with their posting in mus, others by sending their failed master to me, to dissect. Thanks all of you
Overfilling brake fluid reservoir, "may" cause loss of brakes:
IMHO this is number one reason for sudden brake failure.
Over filling; Such a small thing, most Toyota Master ASE certified mechanics, will say makes no difference. Most are not even aware; Toyota embossed instruction on topping on the brake reservoir. Even spillage on reservoir can have same effect.
If brake fluid aloud to run down side of reservoir. Fluid may get on the wires and/or into its sheathing. Fluid may then travels down the wire(s) into the boots.
Brake fluid is hygroscopic (pulls moisture from the air). If brake fluid gets in the boots of the brake control wires, which are resistance wires. The wire terminals, nuts & screws will corrode from moisture in fluid. This corrosion will increase resistance of wires, causing the commutator to prematurely wear out. IMHO: This is leading cause of motor failure.
Overfilled brake reservoir or fluid spillage, effect on wires, seen below.
A second cause for brake booster motor failure. Is excessive long run times:
Motor running excessively long, each time it is called (pressure in system low) on to run. This happens most often due to a leak or air in system. Leak is not always external (internal pressure leak). Internal pressure leak, will not cause fluid level to drop. Note: level drops naturally with pad wear. I'll touch on this subject later. But if we hear the screeching sound when motors is running and may see bubbles (wake in fluid seen) come up front of reservoir. This is internal pressure lose. The master will need replacing, or pump will run excessively long. Pump is designed for short run time. Running to long each cycle, can overheat the motor. This (heat) too cause premature wear of motor.
A third cause for motor failure.
Brake fluid, gets in the motor from passive seal in the pump, which is not a pressure seal. It's the seal seen when motor pulled off the pump.
What happens is the motor air vent become clogged. The pump has weep drain canal on face of pump, where motor mounts to it. The pump also has a air vent with boot cover next to the drain canal The motor's mounting face plate, has an air vent hole leading to this air vent boot. This air vent is designed to reduce the vacuum (negative air pressure), built up inside motor, as it spins at high RPM. If the air vent gets clogged, brake fluid is then sucked from passive seal weep area of pump, into motor. If weep canal drain is also clogged, it suck brake fluid out past passive seal from the pump. The brake fluid then soaks/damages the rubber insulation in the motor. This brake fluid can also damage motor bearings. It "may" also affect resistance within motor, by affecting contact between brushed and commutator and or windings IDK.
Pump and motor with clogged vent pictures:
Pump (side motor attaches to)
Motor
Motor & Pump
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