LX470 ABS Alarm (2 Viewers)

[shane431]

This morning got in the LX470 and the ABS brake alarm went off for about 2 mins with lights on the dash. I just had to move the car to a different parking spot so I drove it around the block very carefully. I kept checking the brakes but never lost pressure. Well then the alarm and lights just went off. Everything functioned as normal. I turned the car off waited a few minutes then turned it on again, no alarm this time. It's got 287K miles on it so it's plenty broke in. Time for new master cylinder or something else I should be checking?

 

[SteveH]

Per various threads here, pump your brake pedal 40 times (engine off), open the hood, note the brake fluid level, start the truck and time how long the brake motor runs (you might need to be in a quiet garage to hear it). Listen to the sounds the motor makes. It may briefly stop for a second during this pump-up procedure. Note the brake fluid level after the pump-up - should be considerably lower. If the motor run time is more than 42 seconds, or the motor sounds bad, you have a problem.

I got no warning - 15 pumps after the alarm went off, I had (almost) no brakes. My brake motor brushes were shot at 311K, and took out the commutator. I bought the entire accumulator assembly and all is well.

 

[shane431]

I checked this and my motor only ran about 25 secs.

 

[War Rig]

I get this issue every once in awhile due to a bad connection to my brake light. Luckily the light stayed on long enough one time for me to read the code and some searching on here allowed me to realize what it was. So I guess what I'm saying is if the light didnt hang around long enough for you to check it, that would be my personal prime suspect. What to do about it? Check the code if/when it pops up again.

Edit- my apologies, I somehow missed the part where you got an auditory alarm. Yeah that's a problem. My bad. Are your brake fluid levels fine?

 

[shane431]

The fluid level looks fine. I'll check it again. What's strange is that it stop doing it. Like right now when I go start it, no alarms, nothing. Also, I'll plug in techstream and see if I can pull any codes.

 

[2001LC]

25 second booster motor run time, after full evacuation of booster accumulator. Is what I see with brand new booster w/master assembly (the whole deal), and battery voltage at ~12.7 volts. (lower voltage, long the run time)

Procedure for checking fluid is on the brake reservoir.

If level okay, you likely had a pressure issue. This can be as simple as weak seal(s) in system. Where they're not holding full pressure when cold. Warm up by use and all good again.

OR

May be booster motor failing. Sometimes, brushes of motor lands on dead spots of commutator. We get intermittent motor failure.

Condition of brake fluid, staining in reservoir and control wires. Can give vert helpful clues!

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

 

[shane431]

Brake fluid is good. the code was C1256. accumulator low pressure malfunction. Of course I can't get it to do it again. I think it might be the seals as stated. I think i'm going to flush the brake fluid and freshen it up and keep an eye on it.

 

[2001LC]

You've not stated your year. Be good idea to: Post up pictures of you reservoir as you empty to flush. Also a post picture of contacts, of brake booster motor control wire.

Note: Weak seals resulting in alarm. Is typically heard first, at beginning of winter in cold weather.

 

[shane431]

It's a 99. And it was definitely cooler out yesterday morning compared to Sunday. Short term, I'm flushing the brake fluid. Long term, I'm planning on replacing the whole master cylinder set-up. It's getting about that time.

 

[2001LC]

A 99 with 287K miles, is not likely to have a 25 second booster motor run time. I'd run test 3 more times, check battery voltage as I did. Also count how many pumps of brake pedal until evacuation (pedal pressure drops off).

Where as flushing is a very good thing, as it removes moisture. It will not repair damaged seals. It's proper flushing on regular basis, that helps protect seals.

 

[shane431]

A 99 with 287K miles, is not likely to have a 25 second booster motor run time. I'd run test 3 more times, check battery voltage as I did. Also count how many pumps of brake pedal until evacuation (pedal pressure drops off).

Where as flushing is a very good thing, as it removes moisture. It will not repair damaged seals. It's proper flushing on regular basis, that helps protect seals.

You were right! I hadn’t been pushing the pedal all the way to the floor. It was like it has a false stop mid stroke. Anyway retested and it was 38 secs. So I drove it around the block and the alarm came back on and shortly after the brakes were gone! It appears the motor isn’t running at all now. Time for new MC!

 

[nissanh]

Spot on "A 99 with 287K miles, is not likely to have a 25 second booster motor run time"
When I installed the OEM new unit, it is running 25 seconds on an overnight start.

 

[2001LC]

FYIW:

I use only Toyota brake fluid.

I start by flushing all fluid out a rear bleeder. As we only need key on, brake pedal pushed down and rear bleeder open. This is of course, if you can get booster motor running. A few taps on motor with metal bar, it may fire up.

Just disconnect wires from Charcoal canister and lower drain hose. Remove bolt and lift from out of bracket (leaving bracket on body). Set near engine head, with top hoses attached. removing hose may cause leak.

No need to remove dash molding. Just reach under with long extension.

Use a 10mm flare nut wrench.

I begin bleed of new master, by flushing out through rear bleeders. You'll fine bleeding a little more difficult, when installing new master. Going around second time is best.