Abs Accumulator Fail? (1 Viewer)
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Accumulators can lose their nitrogen charge over time and not hold pressure. Personally I have only heard of one or two accumulators failing, and the signs start popping up long in advance (mainly the motor running every two or three brake presses instead of 10-ish).
With the age of these things it’s not a bad idea to change the whole unit.
With the age of these things it’s not a bad idea to change the whole unit.
Wait, I thought 2-4 presses was normal before the booster motor kicks on?
I’m only going from another member’s experience and faint memories of when our 100 was much younger. But the accumulators do lose pressure over the years.
2001LC
SILVER Star
The booster motor is the most common failure point that gives little to no warning. It's failure means we've no brake line pressure assist when pressing brake pedal. This is the scariest and most dangerous condition.
Something I've become aware of is the resistance wire that connects to booster motor. It's considered a non reusable part by Toyota. I now check the wire during inspections for corrosion. I find about 30% of them have corrosion/rust. I suspect this corrosion is due to overfilled brake reservoir, then brake fluid leaking on wires and getting into boot. This corrosion may increase resistance. Which the higher resistance may lead to earlier than normal motor failure. It may also lead to ABS unit failure.
If I was too PM (preemptively maintaining) brake master. I'd replace/rebuild motor for sure and replace wire w/boots along with its screws and nuts. I'd do this around 250K miles (normal HWY/city ratio with normal braking). If wire corroded I do sooner.
Other parts of Master brake assembly:
I'm interest in your used brake master assembly parts. I've been tearing them down to see what I can learn from them. Please PM me, if you end up with some old parts you be willing to ship to me.
Something I've become aware of is the resistance wire that connects to booster motor. It's considered a non reusable part by Toyota. I now check the wire during inspections for corrosion. I find about 30% of them have corrosion/rust. I suspect this corrosion is due to overfilled brake reservoir, then brake fluid leaking on wires and getting into boot. This corrosion may increase resistance. Which the higher resistance may lead to earlier than normal motor failure. It may also lead to ABS unit failure.
If I was too PM (preemptively maintaining) brake master. I'd replace/rebuild motor for sure and replace wire w/boots along with its screws and nuts. I'd do this around 250K miles (normal HWY/city ratio with normal braking). If wire corroded I do sooner.
Other parts of Master brake assembly:
- ABS failure just means no. The ABS, VSC or ATRAC lights come on but we still have brakes.
- Pumps don't usually just fail suddenly. They weaken over time and increase pressure build-up time (long motor run time). Note leak or air in line also results in long motor run time.
- Accumulator failure is rare and generally is not resulting in sudden on complet pressure loss, just weak pressure.
- Master cylinders leaks result in spongy pedal, not sudden brake failure.
I'm interest in your used brake master assembly parts. I've been tearing them down to see what I can learn from them. Please PM me, if you end up with some old parts you be willing to ship to me.
Very interesting on the resistance wire bit. One of the local LandCruiser mechanics noticed this 2 years ago and has replaced the resistance wire with his own (built himself) on several cruisers that were appearing to have failing ABS units. They started working again and have been fine since. He said the harness he built is about $25.
Sean at LandCruiser Specialists (up off 183). He's the one dude I trust with my Cruiser.
2001LC
SILVER Star
Someone just asked if I could build the wires. I said; I'd not try until I've a new set to match resistance with.
2001LC
SILVER Star
I also wonder why a perfectly good wire must be replaced just because removed. I then saw the list price $170 of this ~8" of two wire harness with boots and though that's nuts.
But in speaking with a very old friend that is a 3rd generation mechanic. He said price indicates it's a "resistance wire, they are pricey!" These wires are made from specific materiel designed to control resistance and deliver a very specify amperage within our 12 volt system. This amperage is drawn though the black plastic ABS unit on side of master or more correct name; the skid control ECU.
Perhaps the Toyota engineers considered, if wire is ever removed it's likely because and issue arose between motor and or ABS. That resistance may have changed by the this time and best to just replace. The issue as I understand it, is, the load needs to be present to get a true reading of OMHS. This is not only controlled by the resistor (wire and motor combo) but amount of voltage available. Which is controlled by voltage regulator in alternator, perhaps in the skid control ECU as well.. This is all just speculation on my part, in an area I'm very foggy on.
Here is a ABS unit I pulled apart. Had some interest coils, and what looks like resistors and capacitors in it.
In speaking with a aircraft mechanic on the subject of the "Big Three". He noted that when bluing is found at wire connection end, you can bet it has gotten under sheathing effecting resistance. That they test the resistance of wires frequently and find resistance out of spec even without visible bluing. I asked how do you know what the resistance should be, He said: "Compare to a new wire on the shelf". But understand we were not taking about resistance wires, just regular wires. But it would seem if we get a match in resistance between old wire on rig and a new wire on shelf we'd be good to go. But then why didn't Toyota just give us the value????
So too just make a wire or use old wire may appear to work fine. BUT, it may "affect" the ABS/skid control ECU unit and or motor over time adversely.
Loosing booster motor assistance is scary and dangerous. I've said this before "we still have brake at bottom of pedal, just not much" It actually takes two system to fail at same time to not have any brakes with pedal, other than E-brake. The booster system and the front brake circuit must both fail for us to not have any brakes from pedal.
But in speaking with a very old friend that is a 3rd generation mechanic. He said price indicates it's a "resistance wire, they are pricey!" These wires are made from specific materiel designed to control resistance and deliver a very specify amperage within our 12 volt system. This amperage is drawn though the black plastic ABS unit on side of master or more correct name; the skid control ECU.
Perhaps the Toyota engineers considered, if wire is ever removed it's likely because and issue arose between motor and or ABS. That resistance may have changed by the this time and best to just replace. The issue as I understand it, is, the load needs to be present to get a true reading of OMHS. This is not only controlled by the resistor (wire and motor combo) but amount of voltage available. Which is controlled by voltage regulator in alternator, perhaps in the skid control ECU as well.. This is all just speculation on my part, in an area I'm very foggy on.
Here is a ABS unit I pulled apart. Had some interest coils, and what looks like resistors and capacitors in it.
In speaking with a aircraft mechanic on the subject of the "Big Three". He noted that when bluing is found at wire connection end, you can bet it has gotten under sheathing effecting resistance. That they test the resistance of wires frequently and find resistance out of spec even without visible bluing. I asked how do you know what the resistance should be, He said: "Compare to a new wire on the shelf". But understand we were not taking about resistance wires, just regular wires. But it would seem if we get a match in resistance between old wire on rig and a new wire on shelf we'd be good to go. But then why didn't Toyota just give us the value????
So too just make a wire or use old wire may appear to work fine. BUT, it may "affect" the ABS/skid control ECU unit and or motor over time adversely.
Loosing booster motor assistance is scary and dangerous. I've said this before "we still have brake at bottom of pedal, just not much" It actually takes two system to fail at same time to not have any brakes with pedal, other than E-brake. The booster system and the front brake circuit must both fail for us to not have any brakes from pedal.
What’s the issue? I had a sqawking/squealing noise due to a “sticky” high pressure switch. It only heppens when it was cold outside. I gave up on finding a repair for it once I saw the photos of the ABS module’s guts(molded plastic) and replace the complete unit.
- Thread starter
- #16
No issue, other than my wife driving it full time with the kids. After reading the horror stories about failures, I feel like I need to be preemptive.
Since you can remove the motor without removing the whole unit, I would pull it and inspect the commutator for wear. The copper wears down, but good thing there are places that rebuilds them. Thats the only other concern I know of besides my issue and it's something that can fail without a warning(if not inspected).
