All brake lights and alarm on, but brakes feel fine (1 Viewer)

[OzarkAngler]

Hi folks,

A few days ago my 2002 LC started giving me warnings where all the brake lights (ABS, VSC TRAC, VSC OFF, BRAKE) and a high-pitched alarm would come on, but the brakes feel fine. It doesn't do it every time I drive, and usually turns off shortly after I start it, but I want to go through all the trouble shooting steps to find what is causing the error.

Brake fluid is full, no leaks, I tested the pump and it turned off after 27 seconds (not great, but still within spec) and I didn't notice any gurgling in the MC. I looked at the fuses and relays related to ABS but honestly don't know what I'm looking at with those big suckers as opposed to the 10, 15, 20 amp fuses that are super easy to tell if they're blown.

What else should I check before ordering a rebuild kit? I'm still not convinced at this point that it is the MC.

 

[excessive]

i think the alarm is actually a pressure alarm, the accumulator / pump motor may be starting to go out.

 

[OzarkAngler]

I did some add'l research and I think there's a good chance it's the O-ring on the piston, so I ordered the rebuild kit. The alarm really only comes on in the morning or when it's been sitting a while, and generally turns off after the truck warms up. This (with other threads) leads me to believe that the O-ring shrinks when it's cool, not making a good seal, and when the truck warms up the O-ring expands, making a good seal and no issues.

I'm going to rebuild it tonight and see if that fixes it, but if not I'm going to order the pump/accumulator from City Racer.

Brake Booster Pump with Accumulator for Land Cruiser 100 Series, 4Runner, Tundra

Brake booster pump with accumulator for Toyota Land Cruiser 100 Series, 4Runner, and Tundra.This is a wear item that usually requires replacement as the truck approaches 150K miles. Brand new part, not a rebuilt item or rebuild kit. Direct replacement for part # 47070-60010. Applications: '98 to...

www.cityracerllc.com

Will update this thread with how it goes and if it fixes it.

 

[NE Snowman]

Master assembly gets discussed and dissected in this thread, along with other brake info. Worth reading imo.

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

 

[OzarkAngler]

So last night I installed the new piston, but to my chagrine the problem remains, along with some new ones.

The install was easy enough, but some new symptoms have appeared.

First off, the accumulator does not depressurize after pumping the brakes 40+ times. I tried as many as 80 pumps.

When I turn the key to on, without starting, the pump will turn on for about 4-5 seconds, then cut out for a couple seconds and repeat.

The front wheels bled fine, but I can't get the rear brakes to bleed completely. It's slow and there is an endless amount of air bubbles. I have tubing hooked up going to a gatorade bottle partially filled. Working one wheel at a time, I crack the bleeder and pump the pedal. No improvement, just lots of air. I even wedged the brake pedal down and let the truck idle for over an hour and just an endless amount of air.

Brakes are spongier than ever.

I don't pretend to be a great mechanic but I do most jobs myself and I'm at a loss here.

 

[rexington14]

How's your battery charge? If it's low it won't be able to run the booster sufficiently. Take it to an auto parts store they will charge it over night for free. Then completely start over with the bleeding process.

How I bled the rears recently (plenty of threads with more / better instructions):

engine off, key in ON so booster runs, wedge something between the seat and brake pedal to depress the pedal, then crack a rear bleeder, pump will run to push out fluid / air, let it run for 30-60 sec, close bleeder, pump will stop shortly, go back to MC and top off with fluid so you don't run it dry, let booster cool down minute or two, then back to the bleeder to crack, repeat till no bubbles.

 

[OzarkAngler]

Battery charge is fine.

 

[OzarkAngler]

Last night I took it to the dealership since I got tired and frustrated (limped 3 miles there on back roads with my hazards on) . The o-ring/gasket between the reservoir and master cylinder that sits on top of the rear brake ports is either not seated correctly or is bad. I'm guessing it's not seated correctly, but I did go ahead and order new gaskets, so I'll be tearing it back apart and taking a look at that and we'll see if my MC rebuild actually fixed it.

This was actually my going theory but I was just too exhausted to keep messing with it on my own, and explains why I couldn't get the back brakes to bleed - it just kept sucking in air at the MC. It also explains why the motor would keep cutting out. It can't build pressure without a good seal.

Wish me luck in pull-apart round 2.

 

[2001LC]

The reservoir need not be removed. When replacing the master plunger (AKA piston). Some do remove reservoir, to clean, as they're badly stained. Staining is indication of bad brake fluid left in way to long. So if this the case. I suggest you replace the brake master w/booster (the whole brake master).
The reservoir, has 3 grommets between it and master. Two of one size and one of another size. These can be reused, but best to replace if reservoir removed from master.

Remember to bleed accumulator. Key off pump pedal 40 time, then turn IG key on. With a new master, I this do many time, at beginning and end of flush & bleed.

I start flush and bleed at rears. By just holding down brake pedal (no pumping of pedal), w/IG key on. Then open a rear bleeder, and fluid flows. It (booster motor running) also drains battery, So I keep a charger on battery, as I work.

Do not let level drop below low line, while bleeding.

BTW: Replacing plunge may help, with issue you had in OP. But will not likely totally solve. If seal on plunge weak, at holding pressure when cold in the morning. It's very likely, other seals in the master that are not replaceable, are also weak.

Piston are actually in calipers. One in each rear and 4 in each front caliper. Each having and O-ring (with square edges). Bad fluid is hard on caliper piston O-ring also, so they may be weak.

 

[GremlinMobile]

I this do many time, at beginning and end of flush & bleed.

Why do many time when one time do trick?

 

[OzarkAngler]

Mine wasn't stained too badly, but I cleaned it nonetheless.

I was taking instructions from the thread HERE.

I've thought about the other O-rings being in poor condition, but figured I would start here. I'm about ready to put it back together for a second time and will be paying very close attention to those o-rings between the MC and reservoir.

 

[OzarkAngler]

Update: After paying close attention to the o-ring/gaskets when I put it back together, the brakes bled fine, the brake pedal and response feels good, and the alarm and lights went off after several trips around the block. After the test drive I tested the pump and it turned off after 26s.

I found it more reliable to put the o-rings on the MC and fit the reservoir to that, rather than have them on the reservoir and fit it to the MC like I did the first time.

We'll see if this fixes it permanently, I do think a full assembly is in my future though.

 

[GremlinMobile]

26 seconds is pretty good. No matter how much I've flushed and bled mine, my pump cuts off right at 40 seconds. Am I one second away from needing a whole new MC assembly?

 

[2001LC]

Why do many time when one time do trick?

With new master install or a master that has been totally drained of fluid. One time does not "do the trick"!

26 seconds is pretty good. No matter how much I've flushed and bled mine, my pump cuts off right at 40 seconds. Am I one second away from needing a whole new MC assembly?

Over 40 seconds, to charge accumulator (run time, after evacuation of accumulator). Does not mean a whole new master is needed. It just one point, I use to grade a master. The FSM, only uses this as way: To determine if air still in system, that needs additional bleeding to remove.

But it, also gives us use clues as to heath:

• First is any air in system, that needs bleeding out.
• Weak voltage to motor, increase pumping time. I like to see, 12.4V minimum.
• Weak motor, turning pump slower.
• Weak pump.
• Brake flexible line, expanding excessively. Age and climate two biggest factors. Inspecting, while helper hard braking, is revealing.
• Condition of fluid, very bad.
• A leak in pressurized side of system. Any point in master, after reservoir, all the way to caliper piston seals. (reservoir, nor it's 3 grommets are pressurized)
• *** Accumulator charge depletion or ruptured membrane*. If all others okay and brake master grades high. One can replace the accumulator and it's O-ring. If replacing doesn't help, than look elsewhere. If all above had graded well. It may be seals within the master.

 

[GremlinMobile]

With new master install or a master that has been totally drained of fluid. One time does not "do the trick"!

Over 40 seconds, to charge accumulator (run time, after evacuation of accumulator). Does not mean a whole new master is needed. It just one point, I use to grade a master. The FSM, only uses this as way: To determine if air still in system, that needs additional bleeding to remove.

But it, also gives us use clues as to heath:

• First is any air in system, that needs bleeding out.
• Weak voltage to motor, increase pumping time. I like to see, 12.4V minimum.
• Weak motor, turning pump slower.
• Weak pump.
• Brake flexible line, expanding excessively. Age and climate two biggest factors. Inspecting, while helper hard braking, is revealing.
• Condition of fluid, very bad.
• A leak in pressurized side of system. Any point in master, after reservoir, all the way to caliper piston seals. (reservoir, nor it's 3 grommets are pressurized)
• *** Accumulator charge depletion or ruptured membrane*. If all others okay and brake master grades high. One can replace the accumulator and it's O-ring. If replacing doesn't help, than look elsewhere. If all above had graded well. It may be seals within the master.

Very valuable input. Thank you.

So if brake fluid is fresh, and system has been bled and rid of air properly, and voltage is good, that really leaves bad seals as the culprit. Bad seals means they don't hold pressure as well, which means pump has to run more frequently - which might possibly become an issue because it uses the pump more often so it can wear it out sooner?

 

[2001LC]

Yes, if pump run excessively long. Which FSM warns us, to not run longer than 2 minutes. As that will shorten its life. Pump is designed to run often for short duration. Weak seals are one reason, for long run times. But as I said, weak accumulator can also be reason.