brake failure

olalekanbabs

olalekanbabs

New member
2005 SR5 V8 with 91,000 Miles.

My wife with my kids inside the car was driving in city traffic when the brake warning (red) indicator lit up on the dash. She did not notice any major difference in braking power the first few stops after this indicator came on.

As she continued additional warning (orange) indicators lit up - I believe they were the ABS, TRAC and VSC - accompanied by a high pitched audible warning.

Then when she later went to depress the brake pedal, it went to the floor with little resistance and fortunately she was not speeding because of traffic.

I checked the car myself yesterday, the brake fluid reservoir is not empty, in fact I don't seems to notice any change in fluid level for like 2 months now. The front and back brake pads are new.


Mechanics here are horrible, I have had two of them checked and they can't figure out what is wrong with the brake.
 
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Sounds like the master cylinder portion of the Hydraboost unit has given out. Can you pump up the brakes with the key turned off? When you turn the key on, do you hear the accumulator pump kick in? If so for how long? Do you have any other lights on the dash other than the Brake light?

Unfortunately any issue in the Hydraboost unit itself will require replacement of the entire unit itself, which will require a scantool driven bleeding procedure to properly bleed the air from the system.
 
BlackWorksInc said:
Sounds like the master cylinder portion of the Hydraboost unit has given out. Can you pump up the brakes with the key turned off? When you turn the key on, do you hear the accumulator pump kick in? If so for how long? Do you have any other lights on the dash other than the Brake light?

Unfortunately any issue in the Hydraboost unit itself will require replacement of the entire unit itself, which will require a scantool driven bleeding procedure to properly bleed the air from the system.
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I tried, it's not pumping and I didn't hear anything when I turned on the key.

Other lights are ABS, VSC TRAC and VSC OFF
 
Yeah that sounds like a complete hydraulic failure of the Hydraboost unit, oddly enough I don't hear/see many full fledged failures like that for the system. Its not a cheap thing to replace unfortunately and the dealer is going to gouge you for it, though it doesn't sound like there are many competent mechanics in your area either.
 
BlackWorksInc said:
Yeah that sounds like a complete hydraulic failure of the Hydraboost unit, oddly enough I don't hear/see many full fledged failures like that for the system. Its not a cheap thing to replace unfortunately and the dealer is going to gouge you for it, though it doesn't sound like there are many competent mechanics in your area either.
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I just want to confirm if the link below is the brake booster for my car.

03 04 05 Lexus GX470 Toyota 4Runner ABS Pump Master Cylinder Booster Assembly | eBay
 
BlackWorksInc said:
Yeah that sounds like a complete hydraulic failure of the Hydraboost unit, oddly enough I don't hear/see many full fledged failures like that for the system. Its not a cheap thing to replace unfortunately and the dealer is going to gouge you for it, though it doesn't sound like there are many competent mechanics in your area either.
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While rare, I have heard of instances where Toyota will be interested in getting the parts back on rare failures like this. You might contact Toyota corporate and see if they would be willing to consider an out of warranty repair for such a unique failure so that they can get the broken one back and have the engineers rip it apart to see what failed.
 
Does sound like the hydraboost. If I go out and press on the breaks hard and quick, I'll get the same lights with the high pitch noise. It's warning you there is not enough pressure, and there will usually be enough to stop. It's going to cost a few thousand in U.S money.
 
NeutronJon said:
While rare, I have heard of instances where Toyota will be interested in getting the parts back on rare failures like this. You might contact Toyota corporate and see if they would be willing to consider an out of warranty repair for such a unique failure so that they can get the broken one back and have the engineers rip it apart to see what failed.
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I haven't heard of that, but I don't see why it wouldn't be true and its worth a shot. Give corporate a call and see if they will work with you on the issue. Worst case you waste a phone call.
 
Even if Toyota is willing to work with you on the price, I'm certain that such a safety related failure should be considered very serious... if Toyota is serious about safety.
 
I mailed Toyota USA since the car was bought in the States below is their reply;

Response Via Email (Thomas Morita)04/16/2013 10:36 AM
Dear Olakekan Babalola,

Thank you for contacting us.

We appreciate the opportunity to answer your follow up question.

The Original Limited Factory Warranty for your 2005 4 Runner's brake lines is 3 years or 36,000 miles, whichever occurs first from your vehicle's original in service date.

Thank you again for bringing your concerns to our attention.

Sincerely,
Thomas Morita
Toyota Customer Experience
 
BRAKE MASTER CYLINDER. Fits: 2005 TOYOTA 4Runner SR-5 4700CC 32-VALVE DOHC EFI, AUTOMATIC 5-SPEED | Village Toyota Parts

here is where I believe you will find the cheapest replacement

you may be able to rebuild it; however, I've never torn into one and I've heard [MENTION=66389]BlackWorksInc[/MENTION] say many times that they are not serviceable. the way the break down looks though it looks as if you can replace the failing componants it would just be a matter of bleeding the system when rebuilt and releasing any pressure in the system before tearing into it

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If you decide to replace the unit i have the unit from my 2003 4runner that i am not using anymore since i am converting to a power steering hydroboost. Let me know if its something you would be interested in
 
According to Toyota they aren't serviceable items, but there is a 11 page instruction on how to tear them down and rebuild them in the FSM, yet Toyota doesn't want you doing that...

That being said, I tore down my old one to see how to diagnose these units more effectively and/or find more pinpoint methods to isolate issues in the assembly. I haven't really found anything of use in terms of diagnostics yet.

Most shops won't touch rebuilding them with a 10 foot pole and I would be wary of them trying in some cases. You could try and replace just the master cylinder portion yourself (assuming that's the only failed component in the assembly) which is 47201 in the diagram and will come with a new ABS Solenoid Pack/Module. At which point you've still got the old Accumulator Pump assembly, which seems to fail for some members over time anyways.

In my honest opinion, Toyota is probably on the right idea with just replacing the entire unit. They aren't very friendly to being taken apart and you're going to buy half the unit just for the MC portion.

My old Hydraboost unit failed because an O-ring in the MC portion failed, the only issue is that I can't get a new O-ring without ordering half the unit anyways, so I had to get a replacement unit.

I wish you the best of luck and if you do decide to tackle this yourself, this should help you out some:
http://www.toyota-4runner.org/4th-gen-t4rs/120125-hydraboost-brake-assembly.html
 
So you're going to eliminate the ABS and run your brake assistance off the powersteering? I'm a little confused and intriuiged by your idea, pics would be interesting!

Also to the OP, as long as its a pre-'06~'07ish Hydraboost unit from a 4Runner it'll fit your rig. When they released the FJ Cruiser they went to a slightly different design (a hair more compact by the looks of it really.)
 
BlackWorksInc said:
So you're going to eliminate the ABS and run your brake assistance off the powersteering? I'm a little confused and intriuiged by your idea, pics would be interesting!

Also to the OP, as long as its a pre-'06~'07ish Hydraboost unit from a 4Runner it'll fit your rig. When they released the FJ Cruiser they went to a slightly different design (a hair more compact by the looks of it really.)
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No, am looking at buying something like in the link below;

ABS Pump Master Cylinder Booster Assembly 05 06 07 08 09 Toyota 4Runner | eBay
 
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