Booster Pump / Accumulator Noise diagnosis
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The ohm meter you have should be set to 2000 since you want to measure 0 and 1000ohms(1kohm). If the readings when the pressure switch is depressurized and full pressurized are close to each other within 1-2 ohms, the switch is not switching. Its supposed to change resistance since it is connected to the ABS computer. The computer can measure resistance. When it is 1kohm, the computer keeps the pump running until it measures 0 ohms. The low pressure switch works the same way. It can tell when the pressure is low and Not low. This adds redundancy to the pressure measurement.
looking at the picture, i believe the pressure switches are these based on reading the resistor values in the circles.The PH switch resistor is 1kohm. The PL switch is 4.7kohm. The PL switch switches between 1 and 5.7 kohm. This makes sense 1 + 4.7 is 5.7.
looking at the picture, i believe the pressure switches are these based on reading the resistor values in the circles.The PH switch resistor is 1kohm. The PL switch is 4.7kohm. The PL switch switches between 1 and 5.7 kohm. This makes sense 1 + 4.7 is 5.7.
2001LC
SILVER Star
I no longer have that one.
So did you find one to check this on?
The front cover can be removed from any, for your check. Cover has a seal for dust and moisture, not a pressure seal. Important thing is to have area as clean as can be, before opening up.
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2001LC
SILVER Star
@grundsethp you seem to have a good working knowledge of electrical components and such. Do you mind if I ask your background along these lines?
Do you think cold weather could adversely effect these switch?
My thinking has be cold weather and they'd (switch and signal they generate to control) work better. As opposed to hot weather, where my understating, resistance in wiring goes up..
Do you think cold weather could adversely effect these switch?
My thinking has be cold weather and they'd (switch and signal they generate to control) work better. As opposed to hot weather, where my understating, resistance in wiring goes up..
Temperature does change resistance but its very small. Electrical engineers know this and design the resistors to be very different in resistance. For example 1kohm and 4.7 kohm.
riedon.com
My suspicion is this is a mechanical issue with the switch. The pressure switch has a membrane that is in contact with the brake fluid. That membrane flexs back and forth as shown here.
The switch is normally 1 kohm unpressorized and then 0 kohm at pressure. If the membrane starts to break down and has a pin hole, the membrane will have the same pressure on both sides which balances the pressure and the switch does not switch. This means the switch will need to be replaced. It does not look like a replaceable part.
$1200 is a lot for new Master Cylinder for a switch.
So why would it work when hot vs cold. It may be that the membrane is fine but the electrical contacts are worn and expand in dimension and work when hot but not when cold. Generally the lifetime for relays are 5-7 million cycles. The contacts in a relay are similar in a pressure switch. If you assume 150k miles with 25 mph average speed you get 6000 hours. If the switch switches once per minute, that would be 360,000 cycles. So it looks like this switch is falling short in terms of life.
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My suspicion is this is a mechanical issue with the switch. The pressure switch has a membrane that is in contact with the brake fluid. That membrane flexs back and forth as shown here.
The switch is normally 1 kohm unpressorized and then 0 kohm at pressure. If the membrane starts to break down and has a pin hole, the membrane will have the same pressure on both sides which balances the pressure and the switch does not switch. This means the switch will need to be replaced. It does not look like a replaceable part.
$1200 is a lot for new Master Cylinder for a switch.
So why would it work when hot vs cold. It may be that the membrane is fine but the electrical contacts are worn and expand in dimension and work when hot but not when cold. Generally the lifetime for relays are 5-7 million cycles. The contacts in a relay are similar in a pressure switch. If you assume 150k miles with 25 mph average speed you get 6000 hours. If the switch switches once per minute, that would be 360,000 cycles. So it looks like this switch is falling short in terms of life.
I just ordered the whole master cylinder assembly including the brake booster off eBay.
I just rebuilt my master cylinder.
The person I ordered it from offers $100 to return the broken assembly. I wonder if they know something we don't about repairing them.
Could it be as simple as replacing a switch?
I just rebuilt my master cylinder.
The person I ordered it from offers $100 to return the broken assembly. I wonder if they know something we don't about repairing them.
Could it be as simple as replacing a switch?
2001LC
SILVER Star
Ask him why he wants the core.
It could be that he tests the components and parts the unit out. The motor alone can for for over $100 without the booster.
Sorry to revive, but I just experienced this today:
Video 1, pumped the system down. Then started, after 30 seconds it starts squeeling
Video 2, stomping on the pedal to provoke it
To me this sounds like overpressure, and that the accumulator pressure valve is bleeding back to the resorvoir because the pump is overpressuring the system.
Any hints on those switches, or do I have to swap the whole thing? I guess if its a sensing issue it wont help to replace the accu or pump unit.
Video 1, pumped the system down. Then started, after 30 seconds it starts squeeling
Video 2, stomping on the pedal to provoke it
To me this sounds like overpressure, and that the accumulator pressure valve is bleeding back to the resorvoir because the pump is overpressuring the system.
Any hints on those switches, or do I have to swap the whole thing? I guess if its a sensing issue it wont help to replace the accu or pump unit.
I chased it forever, swapping the whole assembly is what worked in the end. No problems since
So you swappe it out for a used unit? Im seeing some rebuilt ones on ebay, but I don't know, my motor is atm working fine, I rebilt my master cylinder a year ago, so that is also good.
A rebuilt unit with new motor and pump might be fine, but if the problem lies within the electronics, are they checked then? hmm...
A rebuilt unit with new motor and pump might be fine, but if the problem lies within the electronics, are they checked then? hmm...
2001LC
SILVER Star
Replace the brake master!
There's a seal in the forward end of master, that is failing to hold pressure. It will get worst. At first it's typically leaks (squeal), when cold. As pressure builds, by booster motor pumping fluid into accumulator. Pressure is released past this failing seal. As brakes use the seals warm. Which at first may swell the seal, enough to hold high pressure. But over time the seal has more or more trouble holding pressure. As pressure drops, booster motor turns on. Booster motor ends up running longer and longer duration. The motor is designed to run often, but short spurts. By running longer duration, it permanently wear outs. Which results in motor failure. Which motor failing to spin, master will have zero pressure. Resulting in sudden brake failure.
I suspect, your reservoir has been cleaned or replaced. I say this, because, it as clean as new ones are. We see this seal fail, where fluid has not been properly serviced over the years. By flushing with Toyota brake fluid regularly. Old brake fluid is dark and their reservoirs stained. Which is a clue of bad seals. A clue you do not show, WHY?
Brakes ...... Overdue write-up.
First and foremost: Brakes should only be worked by those, with high level of mechanical abilities and experienced with brake systems. With the age of all 100 series today, in our aging fleet. Any issue, with brake master assembly. IMHO, best and safest course of action. Have the whole brake...
forum.ih8mud.com
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Well the claanlines of the resorvoir is due to me changing the piston, I claned the resorvoir when I did that, it was pretty dark when I got the car. The pedal was weird and mushy. Firmed right up after I changed the piston and bled the breaks.
So perhaps getting a remanufactured one is an option after all?
So perhaps getting a remanufactured one is an option after all?
I tried rebuilding my master cylinder and then replaced the accumulator.
Beware, I bought an accumulator off eBay that was for a GS. Looks very similar but it is smaller. The listing showed it was for a LX part number.
Nothing worked. Bought a used complete unit and never had another issue.
Hello,
can someone tell me if it is possible (and if so, how) to distingush a "Genuine Toyota spare part" from a "chinese one"? After failing the booster-pump-motor of my HDJ100 (250.000km, brushes and collector complete worn); I ordered this item:
Toyota Land Cruiser Lexus LX470 OEM Brake Booster Pump & Accumulator 47070-60010
It arrived today, the box is labeled with "Genuine Toyota Parts", there is also the Toyota part number sticker. But on the motor/pump item I can´t find nothing that says "Toyota", "Aisin" or something similar... not even a "Hazard, high pressure inside" warning sticker. And now, of course I´m asking myself, if this maybe exactly the same piece like these ones that are sold from China for 2-300$.
I think I shouldn´t doubt; but I also alwas thought, that genuine spare parts of whatever manufacturer wear a sticker, a label, a janpanese-looking scratchmark, anything like that...
Thank you in advance.
btw: The motor failed (without any noise or intermittent failure before) on a trip at nearly the highest with a car reachable point in our province and some 40km and 1000m of hight difference from home. The location is not accesible for a pick-up service truck, so I tried to get to a "official road"... and once there, I remebered that lemma from good race drivers: "The one who brakes, loses the race", so with help of reduction gear, manual shifting of AT, handbrake and my wife´s encouraging words from the passenger seat; I managed to get home. Luckily that happened at 10pm, so there was practically no traffic on the (mountain) roads. The residual braking power by pressing the pedal hard is ridiculous; I used this on the whole way home only once: to stop in the garage at home.
can someone tell me if it is possible (and if so, how) to distingush a "Genuine Toyota spare part" from a "chinese one"? After failing the booster-pump-motor of my HDJ100 (250.000km, brushes and collector complete worn); I ordered this item:
Toyota Land Cruiser Lexus LX470 OEM Brake Booster Pump & Accumulator 47070-60010
It arrived today, the box is labeled with "Genuine Toyota Parts", there is also the Toyota part number sticker. But on the motor/pump item I can´t find nothing that says "Toyota", "Aisin" or something similar... not even a "Hazard, high pressure inside" warning sticker. And now, of course I´m asking myself, if this maybe exactly the same piece like these ones that are sold from China for 2-300$.
I think I shouldn´t doubt; but I also alwas thought, that genuine spare parts of whatever manufacturer wear a sticker, a label, a janpanese-looking scratchmark, anything like that...
Thank you in advance.
btw: The motor failed (without any noise or intermittent failure before) on a trip at nearly the highest with a car reachable point in our province and some 40km and 1000m of hight difference from home. The location is not accesible for a pick-up service truck, so I tried to get to a "official road"... and once there, I remebered that lemma from good race drivers: "The one who brakes, loses the race", so with help of reduction gear, manual shifting of AT, handbrake and my wife´s encouraging words from the passenger seat; I managed to get home. Luckily that happened at 10pm, so there was practically no traffic on the (mountain) roads. The residual braking power by pressing the pedal hard is ridiculous; I used this on the whole way home only once: to stop in the garage at home.
