Screeching from brake Master Cylinder assembly

[Weeniewheeler]

So each morning for a week or so, when I start up the LX I hear what sounds like the screeching of a tortured seagull coming from my Master Cylinder assembly (listen here: noise starts at :23). I have no lights on my dash, and have never lost brake power at all. The screeching lasts about 10 seconds to up to a minute (longer after several days), but once it stops, I have no other symptoms until the next morning. I have read several pertinent threads https://forum.ih8mud.com/threads/brakes-are-totally-screwed.827650/#post-9506608
http://www.toyota-4runner.org/4th-g...8-4runner-abs-pump-problem-any-solutions.html
http://www.fjcruiserforums.com/foru...rake-accumulator-screeching-noise-help-2.html
but here's the thing: I leave for 100s in the Hills in two days, and I do not have time to jack around with half-baked solutions. My mechanic is going to swap out the brake accumulator with a new one ($375 from the dealer) and I hope that will solve the issue. If I lose my brakes and die on Black Bear Pass, you'll know my solution was incomplete and you should suck it up and replace your whole assembly. Otherwise I will return and report whether the fix solved my problem. Here's hoping I'm right.

 

[Ganndolf]

Hey man! I'm the guy from the first link there. I replaced my accumulator at the dealer and it solved my problem 100%. That is a good price you have there too btw. I would also suggest changing out all the fluid when they do it. In industry hydraulic accumulators are considered wear items. The screeching you are hearing is from a thing called fluid hammer which happens when accumulators start to get old. (I talked to a few of my Mechanical engineering professors who specialize in fluid mechanics and confirmed all of this) There are several people I found with 4runners and FJ cruisers who have had their screeching going on for 1-2 years every morning! The pump that pumps fluid into the accumulator must be a pretty strong little thing! but that screeching noise ripped my heart out so I had to fix it! Lt us know how your trip goes. Also, don't worry if you start to hear the pump running on startup a little differently, that is normal. as long as you hear it run every 3-4 hard brake pedal hits or so for a few seconds(its not an exact number) it is working just fine. You can look up why accumulators get old. It can cause alot of things. The nitrogen stored in the bladder can leak out and get into the system and that can cause some weird noises and damage too. Some of my Saudi friends I go to school with also have this problem with their cruisers back home and they replace their accumulators as a PM for the master cylinder problems the 100 has, I found that out after I did mine though, Wish I had known before so I was a little more sure in my purchase haha.

 

[Weeniewheeler]

Ganndolf, thanks for the report. It makes me much less nervous, now.

 

[montegofd3s]

WW any luck getting it fixed? Mine is not nearly as loud as that video, but does have a bit of squeal during start up. I wasn't able to diagnose exactly what it was before leaving for HIH5. I am well on my way there now so it is a little late.

 

[Weeniewheeler]

WW any luck getting it fixed? Mine is not nearly as loud as that video, but does have a bit of squeal during start up. I wasn't able to diagnose exactly what it was before leaving for HIH5. I am well on my way there now so it is a little late.

I pick up my truck this evening. I'll let you know.

 

[montegofd3s]

We can chat over a beer tomorrow.

 

[Ganndolf]

We can chat over a beer tomorrow.

How'd it go guys?

 

[Weeniewheeler]

So, I've been getting over a cold and am finally back in the land of the living. The truck is still making the screeching noise. On top of that, as I was going on the first trail Friday morning at 100s in the Hills, I had a catastrophic failure. The ABS, BRAKE, ATAC and VSC lights light up on the dash, and an alarm goes off. Someone who had a Techstream reset the error code (brake pump failure) and I finished the Imogene Pass run without incident. After returning home from Colorado, the screeching happens when the truck sits overnight and the brake pump failure alarm has gone off again. I've parked the truck until I can diagnose and fix the problem.

 

[Weeniewheeler]

BTW, we noticed that my brake fluid appears old. I thought my mechanic was going to change it but I guess not. I think I'll have to change the booster pump and brake fluid next.

 

[Ganndolf]

That's a good second step, might've been just too late for that pump.

 

[e9999]

tell me you didn't go up a Colorado mountain pass after that alarm and without doing anything about it...

 

[Weeniewheeler]

tell me you didn't go up a Colorado mountain pass after that alarm and without doing anything about it...

Well, we did reset the error code. We listened to the pump which seemed to be running without problem. And the truck ran up and down Imogene flawlessly. Though there were 15 of my new, closest friends in front and behind me to help out if I'd had a problem.

 

[hidesertwheelin]

So mine just made that noise yesterday. Did you end up having to replace the entire MC?

 

[Weeniewheeler]

So mine just made that noise yesterday. Did you end up having to replace the entire MC?

Yup, $2,100 for the part alone. Replaced it and haven't had a problem since.

 

[hoser]

If it is the pump motor, there are few choices.

1) Replace the entire assembly @$2100 plus labor
2) Replace just the Pump assembly @ $1100 plus labor
3) Send the entire assembly off to get the motor rebuilt ~ $300?

With the #2 or #3 option, I would also buy the MC rebuild kit @ $60.

Also note, the pump motor is shared by certain Tacomas, 4Runners and Tundras.

 

[hidesertwheelin]

If it is the pump motor, there are few choices.

1) Replace the entire assembly @$2100 plus labor
2) Replace just the Pump assembly @ $1100 plus labor
3) Send the entire assembly off to get the motor rebuilt ~ $300?

With the #2 or #3 option, I would also buy the MC rebuild kit @ $60.

Also note, the pump motor is shared by certain Tacomas, 4Runners and Tundras.

How do I figure out if it's the pump motor?

 

[hoser]

I don't know of anything else in the booster assembly that could make that sound except the motor. I'm sure there is a way to activate the motor for testing purposes but I don't know it off the top of my head. Look in the FSM. You can pull the motor cover too. If the brushes or commutator are jacked, it's probably the motor.

 

[kcobourn]

Hey so guys what did you choose to do with this?

 

[YodatheLC]

Hey so guys what did you choose to do with this?

Asking because I have the same noise.

Are you saying I have a $2k part that's going out?

I think I'm going to be sick.

That's affirm on the price of the part.... probably the most expensive repair you would ever have to do on this truck.

 

[OverlandOutdoors]

Hey so guys what did you choose to do with this?

Asking because I have the same noise.

Are you saying I have a $2k part that's going out?

I think I'm going to be sick.

What was the fix for you? I have the same exact noise and problem. I replaced the booster pump with an ebay rebuilt one but still have the same issue?