Brakes ...... Overdue write-up. (3 Viewers)

[NE Snowman]

Yup

Another tip, most here don’t use the search function on mud. Use google or your favorite search provider and do “ih8mud 200 series “ + your question. It’s a much better way to find threads related to the search.

 

[Wstclx2001]

Your in 100 series section.

200 series is redesign, better boots/wires. So not seen, fluid overflow wire issues. Key off pump is less, but 40 is fine, time to charge less IIRC.

Best, you list your vehicle in signature line, or repeat in every post.
Best, you ask question in 200 series section. If you don't see me and need too, PM with link to thread you need help in.

Ok will add signature. Don't know why i thought this was 200 forum! I think i googled it and saw that it was related but i guess I'm mistaken. Thanks for your help!

 

[jimmypeod]

Recently started having issues where I get brake dash lights and alarms for a few seconds. Very sporadic, sometimes while driving, sometimes while idle. I haven’t ever lost brake pressure, and braking has felt consistent the whole time. Pump takes about 35-36 seconds during testing and I don’t see any leaks. However, I bought the truck used and there was a bottle of valvoline “premium-dry brake fluid” in one of the drawers. Where do I start to try and fix the problem? Or do I need to go straight to replacing the whole thing? Thanks.

 

[Unrulykid]

]

Recently started having issues where I get brake dash lights and alarms for a few seconds. Very sporadic, sometimes while driving, sometimes while idle. I haven’t ever lost brake pressure, and braking has felt consistent the whole time. Pump takes about 35-36 seconds during testing and I don’t see any leaks. However, I bought the truck used and there was a bottle of valvoline “premium-dry brake fluid” in one of the drawers. Where do I start to try and fix the problem? Or do I need to go straight to replacing the whole thing? Thanks.

Read through this thread from Post #1… will provide insight how to self diagnose your issue, and recommendations for prevention. Read through to glean as much info and background as you can.

You can look up any parts you may need on Partsouq… enter your VIN number for most accurate part numbers.

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Historically, right around Black Friday, Toyota online parts center usually offers 25% off plus free nationwide shipping. With the nature of the import tariffs that we are seeing in the United States right now, would probably be most cost-effective to purchase in country, rather than from overseas.

I don’t know how many miles on your vehicle, but if the brake master cylinder has been neglected, or it has been fed a diet of non-Toyota OEM brake fluid, your master cylinder may be in a state of decline, as described by 2001LC.

If you need help from the community, please provide the specific details of your situation. Because those will be the first questions that the community asks of you.

What year?
Current mileage?
Service history?
Rust and corrosion condition?
Current brake service status? Worn pads?
Any codes?
Any wiring anomalies? Bootlegged half assed wiring by PO?
Non-OEM components?

This information will help the community to aid you in diagnosing your issues over the Internet.

 

[2001LC]

Recently started having issues where I get brake dash lights and alarms for a few seconds. Very sporadic, sometimes while driving, sometimes while idle. I haven’t ever lost brake pressure, and braking has felt consistent the whole time. Pump takes about 35-36 seconds during testing and I don’t see any leaks. However, I bought the truck used and there was a bottle of valvoline “premium-dry brake fluid” in one of the drawers. Where do I start to try and fix the problem? Or do I need to go straight to replacing the whole thing? Thanks.

If you'd like to stop by , to have me to look over you 100 series. PM (DM) with your contact info.

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ABS alarm and its lights, come on. For the most part, are when pressure drops below a minimum threshold for a specific duration.
Brake light comes on. For the most part, are when E-brake on or when fluid low in reservoir.

You can test your pressure alarm is functioning, and learn what sound and lights happen when pressure drops:

1. By simply, pumping brake pedal rapidly, with IG key ON (engine on or off). The more or less, rapid pumps, before alams. Is also a measure of health of system and fluid.

Note: Engine running, battery is being fully charged. Engine off, battery tends to be at lower voltage. The higher the voltage. The faster the booster motor spins its pump. The faster system builds pressure. That is why, we need to know the voltage, during time to fully charge/pressurize test, from a fully evacuated (40 pumps IG key OFF). Which we do while engine off. Simply because. Engine sounds, may not allow us to hear booster motor running.

We can have alarms, on occasions. When brakes fluid is cool. Especially in mornings, when OAT lowest and brakes haven't yet been used. Cool brake fluid, meaning: Brakes not used for hours, so fluid not under high pressure. Keep in mind; pressure = heat The higher the pressure, the greater the heat generated. So, no thermal expansion when fluid cold. Rubber seals, in the system as well as all materials are contracted (shrunken) when cold. We'll get alarms for just a few moments. Then the more we use the brakes, generating heat. The more the brake fluid heats up, heating all components. Thermal expansion! The system now holds pressure, since all components expanded/tightened. So alarms & lights clear.

We may or may not see a leak in these systems. But for some reason, system is detecting low pressure. If we can't find the fault, and ABS alarms only when cold and not often. We can watch. If becomes more frequent, we must must take action. Which in most cases these days as fleet has aged. means a new brake booster w/master (the whole brake master).

Other times. Booster motor is running intermialy, when called to run by low pressure. This is very common, when commutator has a few bad spots. Tricky to diagnose. Since we get frick be it running when we check, by jumping with 12 volts.

Short or fault. Can also be inside ABS unit, which current passes through.

One example of not seeing a leak, yet system pressure dropping due to leak. Is when we hear squeal (dying seagull) and see bubbles in resevoir, without even pumping brake pedal. This is internal leakage past a seal in front of master. Often times we don't get a brake alam in these. The seal get worse with each failure to hold pressure. The sound is fluid passing the seals, under very high pressure. As it get worse, motor runs excessive long. Again we burn up motor.

We may also have situation of low voltage to brake booster motor. Thus system takes to long to build pressure.

Dealership, often replace the ABS CPU, as first step. I've yet to see a bad ABS CPU.

Many components in our braking system, must all working together as one. So we look for clues, as to possible problem areas.
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I had one with only 24K miles on it. It had intermittent brake alarm. It was diagnostic as just needing used more. I found a number of issues, i had to work through: low-mile-case-study-24k-07lc

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In another with alarms:
That had alarms for no apparent reason. I had to replace a brake master and found while doing the R&R.

Where ABS alarms and lights where coming on. This would happen occasionally. For the most part, during cold start up (first drive of the day). In just a matter of days, became more frequent.

It's reservoir was only mildly stained, in this 06LX w/230K miles.
Fluid flush with Toyota brake fluid, few years earlier. Unknown what fluid(s) used before then.
About 30 pump, until evacuation. Not bad for age.
Time to pressurize system, for full evacuation (40 pumps IG key off) with 12.5V. about 33 sec IIRC. Not bad for age.
Fluid a little bit on low side, but above low line. Rear brake pads low, wear indicator sounding off. Fluid does drop as pads wear.
Brake caliper and flexible brake lines inspected for leaks. Non found.
The leads/wire at bottom of ABS unit, had been look at few years ago. Which were okay (no corrosion).
2020 pictures of ABS leads.

So this brake system, other than pressure alarms. Graded fairly well in 2020, and now. But I'll admit, I did recheck brake wires under boot. Since I knew hadn't had spillage or resevoir overfilled since I inspected in 2020.

Still I was 98% sure, issue was in the masters. Most likely internal leak or fault in ABS unit.

While replacing the brake master. I found the leak. It was, at the ABS unit.

Wet ABS, in 2025

Wet ABS side of wires, in 2025

wet motor side wire, in 2025.

New master problem solved.