RTH question......Brake Booster ABS light and Warning (1 Viewer)

[flintknapper]

Yesterday morning (cold morning) started up the LX and an ABS light and warning buzzer came on. Never happened before. Pumped the brakes a few times and it went out. All was fine for the rest of the day. This morning (even colder) same thing (ABS and Warning) but this time it would not correct itself.

I turned the vehicle off, pumped the brakes about 50 times (until the pedal went soft) then turned the key on. Popped the hood and observed. I could hear what sounds like a relay up by the battery click, then the booster motor jwould come on and run for a few seconds then turn off. I checked the brakes and had pressure but the ABS light and Warning continued.

I tried several more times (pumping brake pedal) and noticed that sometimes the motor would run and other times it would not. I tapped on the motor and it would run every time I did that but the light remained on and the warning.

Pulled the vehicle down to my shop and at that point I definitely had lost boost. Still had brakes....but no boost.

I haven't yet taken a good look at it or performed any diagnostics, but remember having read about this some before. Currently have all the 'search' links pulled up and am going through them.

Questions before I get too deep into all the reading:

1. What are the likely issues (replace pump/accumulator and rebuild the master cylinder while out)?
2. Pump motor only?
3. When/how do you determine if the whole shebang needs to be replaced?

I can post back here later my findings....but need a little direction where to start.

I will check the wire connections at the motor first thing....I know that can be a problem but this unit is the original and I suspect will just need replacement. If not now....will need it in the foreseeable future.

Would this be the correct part?

 

[JunkCrzr89]

Just to cover the bases, pump the pedal with engine OFF until it drops out and then check the fluid level in the reservoir. Battery voltage good? Do you have Techstream to pull the ABS codes and troubleshoot the system?

 

[flintknapper]

Just to cover the bases, pump the pedal with engine OFF until it drops out and then check the fluid level in the reservoir. Battery voltage good? Do you have Techstream to pull the ABS codes and troubleshoot the system?

Battery voltage is good.

Will do the pedal pump and fluid level and check back. But when I did that earlier this morning the fluid level was above the MAX line. But will double check that and post back. Thanks.

I don't have techstream but have this ordered:

Amazon product ASIN B075MQDVDV

 

[ramangain]

Oh boy, why would you not get Techstream instead? Especially since (IIRC) Techstream allows you to perform the ABS "bleed" routine (right?).

 

[flintknapper]

Oh boy, why would you not get Techstream instead? Especially since (IIRC) Techstream allows you to perform the ABS "bleed" routine (right?).

Want something I can keep in the vehicle along with the tool-set and spare parts I have onboard.

 

[flintknapper]

So....this is where we are right now.

After pumping the pedal to boost failure (engine off) this is the level of the reservoir:

After running the pump for awhile (approximately 5 minutes, pump motor runs about 3 seconds each time):

Checked the screws on the motor and one of them has corrosion, not terrrible....but not good.

After pumping down the booster when I turn the key to (ON) the pump cycles about every 10 seconds and the motor runs for about 2.5 to 3 seconds, then it repeats over and over. Sometimes the pump motor will run after the relay clicks, other times I have to tap the accumulator to jar the motor and then it runs.

But the ABS and alarm are on constantly. I DO get a hard pedal after the pump has run several times, but the alarm persists....so something isn't right.

 

[flintknapper]

Battery Voltage is fine.

Removed excess brake fluid (reservoir was overfilled somewhat) not that it should make any difference. Got the level correct (boost off, 40 pumps of pedal). Went to run the system and now the pump motor is not working at all, not even tapping will get it to go.

So.....next course of action?

Voltage with alternator running agrees with ScanGauge:

Leads disconnected, battery at 'rest' immediately after disconnect:

 

[Skidoo]

Kind of sounds like brushes were going out on booster motor, but try cleaning up that connector to see if that will fix it.
Might as well rebuild the MC while you are there, those O-rings are getting old if original.

 

[flintknapper]

Order pump motor and accumulator or more diagnostics be more prudent?

 

[flintknapper]

Kind of sounds like brushes were going out on booster motor, but try cleaning up that connector to see if that will fix it.
Might as well rebuild the MC while you are there, those O-rings are getting old if original.

Have a MC kit on the way already, had planned on that. Agree that the motor is most suspect and likely brushes. Thinking just replacing the booster motor and accumulator might be the most expedient thing. Hoping the entire ABS isn't the issue.

My fluid is somewhat dirty as well....so a flush is in the cards too.


Guess I need to look at what it takes to get this thing off of the vehicle. Not the best timing, waiting on my Covid test to come back, feel pretty lousy. But we'll soldier through it.

 

[Eicca]

Just did mine on my Lexus GS. Wasn't anywhere near as hard as I expected, so I imagine the LC is even easier with that extra room under the bonnet.

I recommend undoing things in this order: First the brake pedal pin and spring, then wires/electrical, then brake lines, then the four bolts in the driver's footwell. Reinstall in reverse.

A wobble joint and some extensions make reasonably quick work of the under-the-dash part.

 

[flintknapper]

One other question: Is the booster pump supposed run continuously or does it cycle (under normal conditions)?

 

[neoworm]

It cycles but should run between 30 and 40 seconds in total

 

[Ayune]

One other question: Is the booster pump supposed run continuously or does it cycle (under normal conditions)?

After initial pressurization when starting the car, the booster will cycle only when the system pressure drops and needs to be re-pressurized. When applying the brakes the pressure drops slightly, so the booster will come on often during around-town driving.

It shouldn't come on after every brake application, though. That's indicative of a pressure leak somewhere (master cylinder?).

 

[jerryb]

You've read paul's dissertation right?

 

[flintknapper]

You've read paul's dissertation right?

I've read until my eyes are bleeding.....yes. Paul's excellent writings as well as other accounts of outcomes, failures and success.

I'm going to go with the most 'common' cause (with respect to my symptoms) which is the pump motor, but I see no reason not to also replace the accumulator, so looks like I will most likely order that assembly, rebuild my M/C, flush the system and see what we end up with.

 

[jerryb]

If it was me. I'd order order the pump and accum.

I'm dreading the day I see this. And fwiw, the price of the complete assembly is going up year after year.

 

[flintknapper]

If it was me. I'd order order the pump and accum.

I'm dreading the day I see this. And fwiw, the price of the complete assembly is going up year after year.

^^^^^
Agree that seems the best route to go. Will be ordering today.

 

[thebeedeegee]

What makes you think it's not just the pump and you could just have that rebuilt for a a few hundred bucks right?

 

[JunkCrzr89]

What makes you think it's not just the pump and you could just have that rebuilt for a a few hundred bucks right?

Only the motor can be rebuilt.