Brake Gremlin

[SocalSam]

Seized front caliper: I can feel that my T4R is pulling to one side when braking harder... a sign for a dragging caliper.

another idea came up.
The ABS is probably part of the equation here. Can a contaminated ABS modulator cause a soft brake? There are probably internal solenoids and valves... debis might cause malfunctioning of the brakes in general?
Has someone taken the ABS apart for cleaning purposes?

Martin

I'm learning more about our brake booster system in this thread so I feel like I am replying for my benefit more than for our OP. My apologies. When I got my 2003, it pulled hard to the right at freeway speed with sudden brake application. I learned how to drive around this which gave me time to look rotors over. I did not see uneven wear. And then my booster pump failed making this awful noise:

https://www.youtube.com/watch?v=EbhZzsfan6o

I never lost powered assisted braking so bad motor bearing was the obvious diagnosis. I replaced the motor and accumulator as an assembly which solved the problem. Unexpectedly, the pull to the right went away with the bad motor. I had the brake assembly our of the car and most of the brake fluid drained out. I can only guess that debris was blocking the filter screens and drained out with the fluid thus curing the pull.

One more observation to offer. With engine on and car in park, I stabbed the brakes to see when pump would come on. It was once every three applications and for about 5 seconds. From the many posts I have read on line, this seems to be a common experience. Owners report no braking issues even after years of this.

 

[werminghausen]

In your very 1st post in this thread you stated...

"I have not had a car with such complicated brake booster/ABS than the 4th Gen.
My brakes quit 3 years after I bought the 4th Gen (2002 model)."

My question is what year is your T4R actually, a 2002 or 2003, I ask because a 2002 is a 3rd Gen not a 4th gen?

That being asked, at this point I would replace the entire master cylinder/booster assembly, a bit pricey at about $1300 to $1350 +/- depending on source but it should solve all of your issues provided you get all the air out of the system after installing the assembly.


Hi Auseeker,

I misspoke, I have a 2003 T4R with a 4.7 V8. So I have this diffcult to maintain electric motor assist Brake/ABS unit that is not well understood (by myself) as I simply know the old system with the idiot proof vacuum booster and add on ABS of my older Mercedes.

As I know hydraulic systems very well (I am a mechanical engineer) i would need the hydraulic diagrams or true sections of this unit and some data in order to understand the functions, maintenance and repairs better.
I believe I could do a much better job this way and don't ask stupid questions.


For sure I could buy a new unit and install and most problems would be solved... but I love these mechanical challenges and I am happy to drill into it and learn.

I'll look into the manual excerpt.

Thanks, Martin

 

[werminghausen]

One more observation to offer. With engine on and car in park, I stabbed the brakes to see when pump would come on. It was once every three applications and for about 5 seconds. From the many posts I have read on line, this seems to be a common experience. Owners report no braking issues even after years of this.

Yes I can confirm a similar experience when my brakes worked well in the past.

Right now the bake motor comes on at every second application for about
15 seconds.

It is not only that the motor comes on more often but also much longer each time.

This could indicate that my currently installed ' rebuilt accumulator' is very weak.
An accumulator with lower charge needs more oil volume pumped into the accumulator in order to reach the system set pressure.
So far this is my theory.

I reached out to the place where I bought the rebuilt unit on ebay and asked the question to what pressure they were charging the accumulator they sold me as 'rebuilt'..... no answer so far.
My guess is they did not do anything to the old accumulator because the filling valve on top still has the original old painted seal.... they simply sold an old accumulator as 'rebuilt'.

Martin

 

[AuSeeker]

In your very 1st post in this thread you stated...

"I have not had a car with such complicated brake booster/ABS than the 4th Gen.
My brakes quit 3 years after I bought the 4th Gen (2002 model)."

My question is what year is your T4R actually, a 2002 or 2003, I ask because a 2002 is a 3rd Gen not a 4th gen?

That being asked, at this point I would replace the entire master cylinder/booster assembly, a bit pricey at about $1300 to $1350 +/- depending on source but it should solve all of your issues provided you get all the air out of the system after installing the assembly.


Hi Auseeker,

I misspoke, I have a 2003 T4R with a 4.7 V8. So I have this diffcult to maintain electric motor assist Brake/ABS unit that is not well understood (by myself) as I simply know the old system with the idiot proof vacuum booster and add on ABS of my older Mercedes.

As I know hydraulic systems very well (I am a mechanical engineer) i would need the hydraulic diagrams or true sections of this unit and some data in order to understand the functions, maintenance and repairs better.
I believe I could do a much better job this way and don't ask stupid questions.


For sure I could buy a new unit and install and most problems would be solved... but I love these mechanical challenges and I am happy to drill into it and learn.

I'll look into the manual excerpt.

Thanks, Martin

I wish you the best of luck trying to understand how these ABS booster master cylinder systems work on these T4Rs, if you figure it out please enlighten the forum!!

That being said even Toyota dealership/Techs know very little on how this system actually works, if you take yours to a dealer they WILL NOT replace any of the parts like the accumulator/motor/pump, they will only replace the entire master cylinder booster assembly, there is nothing in the Toyota Shop Manual on servicing this system other than the bleeding process and how to R&R the complete assembly.

We even have a couple Toyota Master Techs as members here and they say the same.

How the actual master cylinder works is basic hydraulics, but it's the ABS booster portion that is the mystery and I think that lack of available knowledge is intentional on Toyota's part!!

That lack of knowledge could be because of possible liability issues for Toyota is my best guess since it's the brakes.

 

[SocalSam]

Yes I can confirm a similar experience when my brakes worked well in the past.

Right now the bake motor comes on at every second application for about
15 seconds.

It is not only that the motor comes on more often but also much longer each time.

This could indicate that my currently installed ' rebuilt accumulator' is very weak.
An accumulator with lower charge needs more oil volume pumped into the accumulator in order to reach the system set pressure.
So far this is my theory.

I reached out to the place where I bought the rebuilt unit on ebay and asked the question to what pressure they were charging the accumulator they sold me as 'rebuilt'..... no answer so far.
My guess is they did not do anything to the old accumulator because the filling valve on top still has the original old painted seal.... they simply sold an old accumulator as 'rebuilt'.

Martin

If I suspected a bad accumulator, I would be in there replacing. I kept my recently removed booster/accumulator and I have a spare that I bought cheaply at the junkyard.

 

[usernameinuse]

This thread is disappointing to me because I am dealing with a very spongy pedal right now too. Also in MA! My wife is afraid to drive it because the first push goes almost to the floor. After that all is good, but very spongy.. I thought, no big deal I will just bleed the system but now I wonder if I should have it done because it sounds like a pain in the rear!! No lights and no fade at red lights etc.

 

[rdruss]

This thread is disappointing to me because I am dealing with a very spongy pedal right now too. Also in MA! My wife is afraid to drive it because the first push goes almost to the floor. After that all is good, but very spongy.. I thought, no big deal I will just bleed the system but now I wonder if I should have it done because it sounds like a pain in the rear!! No lights and no fade at red lights etc.

Did your problem just come out of the blue or is it after doing some brake work?

 

[werminghausen]

Update today.

My wife was driving the T4R and the brake alarm happened to her as well.

She is a super defensive driver and I can't believe that the alarm went off with dash light (ABS/VSC/TCS) and the high pitch sound.
She was driving by herself and came home scared- alarming indeed.
We will not drive this car until the problem is solved.


As this problem is coming back... did anyone experience this alarm by simply normal driving? (note: the brake fluid level is nomal).

Best, Martin

 

[MikeinNH67]

I've only had that alarm when either working on the brakes or had a bad brake line. That will freak ya out, it's pretty loud. If I was you, I'd pull a caliper at a time, compress the pistons and then fit a block of wood in there tightly with shims. Check for pedal squish after each one. If no change then I'd be thinking that reman unit is poo. After some web searching, it seems there could be some codes set from the alarm. That could give some direction if so.

 

[werminghausen]

Hi Mike,

I tried to do a reading... have not done it before on the T4R.
I have this reader available from my neighbor.
Innova 3040d : no faults

I'll decommission this poor braking car now due to safety issues and
will install the new accumulator (an perhaps look at the ABS block) and examine the front calipers.

Does anyone have the part numbers/ data for ordering the 2003 Brake caliper repair seals?
Martin

 

[werminghausen]

I found the repair kit number for the front calipers (diameter 45.5mm)

Dorman MAS D670011 Front Disc Brake Caliper Repair Kit, around $25


Martin

 

[MikeinNH67]

Well that's a bummer. I wonder if it would have showed a code when the alarm went off. It will be interesting to hear what the eventual issue is.

 

[werminghausen]

short update.
Since the incident with the alarm lately ( full brake alarm with all dash lights on plus sound) I did not drive, just moved the car around on the property. After starting the engine all alarm lights are off in Park.
But each time I start driving the brake the VSC TRAC / VSC OFF dash light comes on and stays on until I shut down the engine. The ABS light is NOT on and the sound is NOT there... strange.
I did not have this combination before. What do these VSC lights mean?
I have the feeling this new VSC light might be something else? Not sure if this alarm is related to the brake or not?
That Toyota brake VSC is a gremlin... also because there is no technical explanation from Toyota what these lights indicate (technically) and how this can be fixed.... In the owners manual they say simply ...visit your Toyota service.

Maybe someone can explain the VSC lights?

Martin

 

[rdruss]

My guess is that the code reader you used set those lights on. I have an '03 and I bought a ScanGauge, but I quit using it because it would set those same lights on. There's a simple way to get them to go off, I used it and it worked. Google VSC light Reset and you'll get the video.

 

[werminghausen]

Very helpful rdruss!
I did not know that there are good and bad OBD scanners...oh my.
My interpretation... nothing is wrong with the car. Just another gremlin

I'll try out that paper clip magic. Not a woodoo fan but if it helps....why not.

Martin

 

[werminghausen]

The trick worked! The VSC warning light seems to be gone.

Thanks again.

Then I was driving on my property some more (to test if the VSC warning light is returning- it did not) and I experienced that the brake booster motor was coming on even more frequently than before.
It came on every time I hit the brake and it came on oftentimes when I turn the key into ignition without starting the engine.
So indeed the frequency the booster comes up has increased now to a point the car cannot be driven any more... That low storage capacity of the break fluid accumulator is probably why the brake alarm was causes the freqent brake motor noise refilling the accumulator.

Time to install the new accumulator.

I'll report back when I am done.

Best, Martin

 

[werminghausen]

update today

I took the T4R on the lift and removed the brake booster/master cylinder unit.

I removed the so called 'remanufactured' accumulator from ebay and did the pressure test for the nitrogen charge: It measured 43 bar charge.
The new accumulator I bought measured 75 bar.
Typically a 20% loss of charge results is the absolute limit (75 x 0.8 = 60 bar minimum). Remember my original unit had reached the limit of 60 bar.
43bar is way too low (43 bar means only 57% of the charge left).
I feel it is cheating and in fact criminal [ in the case of a brake system that affect the safety] that people on ebay sell a 'remanufactured unit' and it is simply a unit from the junk yard that they resell as remanufactured.
I can see that the seller did nothing to the unit (the accumulator has still the original color at the charging hole... in fact it is not rechargeable, unless you install a new charging valve).
All my emails to this seller are unanswered... Is there a way to stop these guys?

Anyhow I have installed the brand new accumulator that tested positive (75 bar) and I still need to do the bleeding (bleeding. the master cylinder and the brake lines).

I am thinking about removing the front calipers and check them for seized pistons before I am bleeding the calipers.

Best, Martin

 

[AuSeeker]

Have you reported the seller to eBay??

 

[werminghausen]

Have you reported the seller to eBay??

Not yet! I tried a last time to contact the seller but told them I will reach out to ebay if they are not answering.

 

[werminghausen]

I tried to start a claim at ebay but it seems there is an expiry date on these items, return period is long gone. I might be too late for a claim.... I let it slip for too long.
Anybody know what I can do. Maybe I can leave a bad review.

Anyhow I installed the new accumulator and did the mastercylinder bleeding.
I'll follow up with the bleeding of the calipers the next days. And report back on progress.

Martin