Screeching noise, I think from the master cylinder (1 Viewer)

[hidesertwheelin]

I went out to drive my LX470 to kickboxing class tonight. I started her up and waited about 20 seconds and then drove away. I started hearing a horrible intermittent screeching noise from behind the dash. The noise was heard every 5 seconds or so. I pulled over and it continued, and then went away a 20 seconds or so later. I then went to class. Everything was fine when I left class. It has been sitting for a few days and it had been raining. I didn't get any check engine lights. Brake pedal is fine, no softness. It's a 2000 LX 470 w/ 155k miles on it. I plan on having the brake fluid flushed this weekend. Anything else to look for?

 

[Sandroad]

It's possible you're hearing the warning alarm for brake booster failure. Check out the other threads on that with a search.

 

[2001LC]

No CEL, you may be hearing drive belt, one or more pulley bearings form drive belt area or power steering pump. I don't think flushing brake fluid will help with noise. Lift hood with stethoscope, long bladed screw drive or rubber hose in hand before cold start.

 

[hidesertwheelin]

Does anyone have a sound file of the brake booster warning alarm? I found a thread with links, but the links to the files were deal. This sounded like a goose getting killed every 5 or so seconds. I could heard it plenty loud inside with the radio on.

 

[phippsj]

Booster pump on the MC. Several threads here about it.

Happened to me and bit the bullet and had a new MC/pump assembly installed. Not cheap.

 

[hidesertwheelin]

Booster pump on the MC. Several threads here about it.

Happened to me and bit the bullet and had a new MC/pump assembly installed. Not cheap.

Is there anyway to confirm it's the booster pump and not another part that is easier to fix? Tech stream? I don't have any CEL's, so I'm not sure that would work.

 

[PADDO]

Get the booster motor to run by bleeding down the pressure and then monitor the motor and accumulator while it re charges. Hood open, ignition off and pump the brake pedal 40 times to bleed off pressure. Ignition on (don't start) and the booster motor will kick in, now try and identify if it's the motor brushes/commutator grinding itself to death or hydraulic hammer from the accumulator. Use a long screw driver to your ear, or feel the vibe, stethoscope etc. It will be one or the other I believe. Monitor the differences in brake fluid level between when there is no pressure (fluid highest) and charged (lowest) mine drops around 11mm and this may indicate if your accumulator has lost some charge but not enough to throw a code yet. Time how long the recharge takes, mine takes 29 to 30 seconds, iirc the fsm says less than 40 seconds. This time will vary on things like your battery charge and brake fluid viscosity but it's part of the brake system checkout procedure. You can also check the cold resistance of the motors rotating cct - brushes, commutator and rotor winding - should be around 36 ohms? It's all in the fsm.

 

[Sandroad]

Screeching from brake Master Cylinder assembly

 

[hidesertwheelin]

Get the booster motor to run by bleeding down the pressure and then monitor the motor and accumulator while it re charges. Hood open, ignition off and pump the brake pedal 40 times to bleed off pressure. Ignition on (don't start) and the booster motor will kick in, now try and identify if it's the motor brushes/commutator grinding itself to death or hydraulic hammer from the accumulator. Use a long screw driver to your ear, or feel the vibe, stethoscope etc. It will be one or the other I believe. Monitor the differences in brake fluid level between when there is no pressure (fluid highest) and charged (lowest) mine drops around 11mm and this may indicate if your accumulator has lost some charge but not enough to throw a code yet. Time how long the recharge takes, mine takes 29 to 30 seconds, iirc the fsm says less than 40 seconds. This time will vary on things like your battery charge and brake fluid viscosity but it's part of the brake system checkout procedure. You can also check the cold resistance of the motors rotating cct - brushes, commutator and rotor winding - should be around 36 ohms? It's all in the fsm.

Thanks. I guess I need to wait until it happens again. It happened on Tuesday for the first time. I drove it last night and it didn't happen.

 

[phippsj]

Mine went for almost a year before I broke down a get it replaced. Brakes were fine. Had a trip through the mountains with the family so didn't take any chances.

 

[Stealthmimic]

Well, looks like I've joined the ranks of those having Brake Master Cylinder issues. My year 2000 Hundy developed "The Sceech" shortly after leaving the west coast for Santa Fe. Took it in to a dealer in Santa Fe and they told us it would be $3700 for parts + labor + 10 days to do job. Yikes!! Tech took me aside and told me the likelihood of catastrophic brake failure was remote but that a panic stop that engaged the ABS would likely lock the braking system to the point it could only be disengaged in the shop. Drove home by way of Chaco Canyon, Mesa Verse and Monument Valley (very defensively) without incident.

"The Screech" stops after a few minutes each time the engine is started but goes away after a while -- very unnerving! Still, the brakes functioned flawlessly all the way home (WHEW!!!).

It is apparently the Accumulator. Anyone know of thread or "how to" video on replacement? Total MC replacement parts tab looks like $2100+. Double yikes! Not seeing any specific threads (yet) on what's involved. Any thoughts on where to find additional information on DIY replacement and/or sourcing would be helpful and sincerely appreciated.

 

[kcobourn]

Well, looks like I've joined the ranks of those having Brake Master Cylinder issues. My year 2000 Hundy developed "The Sceech" shortly after leaving the west coast for Santa Fe.

It is apparently the Accumulator. Anyone know of thread or "how to" video on replacement?

Reviving this ... did you ever do this as DIY?

UPDATE 7/22/17: after having my dealer take a look they said it's safe to drive. The reset the braking system computers seemed to clear it up + I just pump the brakes to make sure the booster's loaded.

 

[Stealthmimic]

Hate to say it, but you may be just beginning your odyssey with 100 series LC breaking systems. These are highly sophisticated ABS systems and consist of several very expensive components (accumulator, ECU, mc and a couple others).

The screeching is likely coming from the accumulator motor. The brushes have likely worn down to failure point and the dust they produce gets inside the electric motor and causes screeching as the tolerances on the shaft widen. I spoke with a couple specialty shops and they indicated that while you can continue to drive the truck, screeching and all, if you ever have to go into a mode where ABS is initiated it is likely you will not be able to unlock the brakes without having it towed back to a shop. In other words once the ABS starts to fail you could find yourself in a situation with a fairly catastrophic lock up. That said, my son and I drove my truck 1400 miles before I got it back into the shop for the replacement of the entire MC/ECU system.

I'm usually pretty adventuresome when it comes to working on these trucks. When I looked at doing it myself I realized that this was one of those things that was beyond my expertise. Nor did I have the time to figure it all out. In addition there are some specialty tools required to bleed the brakes and balance the ECU/ABS once the job is complete. Knowing what I know now I might consider tackling it. But last summer we just didn't have that option. Knowing what I know now I might consider tackling it. But last summer we just didn't have that option

I am sad to say that I could not find any rebuilt systems and I ended up spending around $2100 on a new system (note the MC/ABS systems are specific to the MONTH the truck was produced and you need to work closely with Toyota to get the proper assembly for your vehicle). Toyota is pretty good about giving a Land Cruiser association discount if you ask for it.

With shop time and fluids I ended up spending about $3400 on this job. That included all of the installation plus new fluid, complete system fluid flush and new bleeders. Of course I live in the bay area on the West Coast and that seems to be an excuse for overcharging for just about everything. You could probably be able to get a better deal outside major metropolitan areas.

I also did a new timing belt, fan, fan clutch, radiator, tensioners, and pulleys along with new hoses right around the same time last year. It was an expensive summer, but since my truck only had 140,000 miles on it and it was a year 2000 I felt that the investment would be worth it. I love the thing and will probably keep it till I die.