Hydroboost failure?

[Dave_l]

Hello all,

New to the forum and I come bearing bad news. Did a lot of searching on here and I think I'm another victim to the hydroboost failure. Ugh. The fiancé was coming home tonight and she said she had a very hard time stopping. Pressed the pedal, nothing happened. It eventually stopped but not immediately. The Vcs, traction control, abs lights come on occasionally but just installed new shocks and didn't see any broken lines or anything. Figured it was a bad sensor or something until tonight when the brakes went out. The reservoir is full and I can hear the pump turn on. It won't cycle for 30 seconds(only about 10 seconds) or so when I turn the car on but as soon as I depress the pedal, the pump kicks on. So it seems to be working, yes? Unless its not supposed to be turning on every time and should old pressure longer? Once the car is started and running, it doesn't seem to kick on as much. More like regular where it's only after a bit of driving.

I took it around the block and couldn't duplicate the problem which makes it ridiculous to trouble shoot. If it is the abs control module, is it common to be intermittent? Or once it goes, does it go?

One other thing is the car will lurch forward occasionally after coming to a stop. Brake pedal depressed but jumps forward like you let your foot off the brake a little. The car is a 2006 4runner sr5 sport v8 with 140k miles.

Any input is appreciated before we decide on what to do with it. Fixing isn't cheap, as you all know, so I want to be sure before I start swapping expensive parts. Will it show up on a scanner if I take it by a parts store? Even if it's intermittent?

Thanks from a newbie member!

 

[rtuck1]

Hello all,

New to the forum and I come bearing bad news. Did a lot of searching on here and I think I'm another victim to the hydroboost failure. Ugh. The fiancé was coming home tonight and she said she had a very hard time stopping. Pressed the pedal, nothing happened. It eventually stopped but not immediately. The Vcs, traction control, abs lights come on occasionally but just installed new shocks and didn't see any broken lines or anything. Figured it was a bad sensor or something until tonight when the brakes went out. The reservoir is full and I can hear the pump turn on. It won't cycle for 30 seconds(only about 10 seconds) or so when I turn the car on but as soon as I depress the pedal, the pump kicks on. So it seems to be working, yes? Unless its not supposed to be turning on every time and should old pressure longer? Once the car is started and running, it doesn't seem to kick on as much. More like regular where it's only after a bit of driving.

I took it around the block and couldn't duplicate the problem which makes it ridiculous to trouble shoot. If it is the abs control module, is it common to be intermittent? Or once it goes, does it go?

One other thing is the car will lurch forward occasionally after coming to a stop. Brake pedal depressed but jumps forward like you let your foot off the brake a little. The car is a 2006 4runner sr5 sport v8 with 140k miles.

Any input is appreciated before we decide on what to do with it. Fixing isn't cheap, as you all know, so I want to be sure before I start swapping expensive parts. Will it show up on a scanner if I take it by a parts store? Even if it's intermittent?

Thanks from a newbie member!

Well i can not answer all of your questions but i can answer some of them. The pump should run when your first turn IGN on. Mine seems to run for 3-4 seconds then shut off. When moving the pump comes on every 3rd time (roughly) that i hit the brakes.

As far as the lurching forward, mine does the same. If you notice, it is in correlation to the a/c pump kicking on and off. RPMs jump when it kicks on causing it to move forward if you do not have a firm hold on the brakes.

Also, from what i remember, if the system loses pressure like she is describing, the system should make an audible alert that it has lost pressure. At a stand still pump the brakes 20x or so and you will hear the alert i am speaking of.

Good Luck!

 

[Dave_l]

Thanks for the info. I had the car scanned and it came up with a C1223 code. This is the "Malfunction in ABS control system (RX3)/43". Does that confirm I need a new master cylinder system?

 

[rtuck1]

Thanks for the info. I had the car scanned and it came up with a C1223 code. This is the "Malfunction in ABS control system (RX3)/43". Does that confirm I need a new master cylinder system?

Search that code on the forum....I did a quick search and found this...Some of those things are worth a shot.

http://www.toyota-4runner.org/4th-g...-abs-brake-swerve-slippage-light-problem.html

 

[Dave_l]

Search that code on the forum....I did a quick search and found this...Some of those things are worth a shot.

http://www.toyota-4runner.org/4th-g...-abs-brake-swerve-slippage-light-problem.html

Yeah, I saw that thread and my only concern is that she did lose braking abilities last night driving the car. I can't see that happening because of those issues in that thread. My other thought was to bleed the brake system and hope it was a rogue air bubble.

 

[BlackWorksInc]

Dave here are the descriptions of the DTCs as per TIS:

C1223- ABS control system is abnormal (This seems to just be a generic code indicating an abnormality detected in the system and has no real diagnostic value other than the obvious.)
C0200- Front Speed Sensor RH Circuit
C1235- Foreign Object is Attached on Tip of Front Speed Sensor RH

Now all these codes list the master cylinder solenoid as a possible cause (though largely unlikely,) I know a wheel speed sensor going bad/being loaded up seems weird that it would cause brake failure, but I don't know what your wife experienced. Sometimes with ABS systems, depending how aggressively they activate can seem like you have no control of the braking system, which is actually partially true. The system will basically overpower a driver's input and do the majority of braking for you via manipulating the solenoids; most people mistakenly believe that ABS will shorten stopping distance, this is false. ABS helps straight line stability in an emergency situation and can in some cases increase stopping distance in an attempt to maintain stability. Traction control also works via the ABS hardware, but it is designed to increase over all vehicle stability in various conditions; the two combined with false or erroneous readings can cause the system to aggressively overpower the brakes and feel almost as if you have no stopping power.

The 4Runner brakes are very soft in travel (almost GM style...) to ease use by "soccer moms," so it can be hard to tell sometimes when they start failing. The fact you state that the brake pedal jumped back a bit makes me think of the system engaging improperly. So first lets address the C0200 & C1235 by checking the Front Passenger (Right Hand) side wheel sensor ring, sensor, and wiring; while you're at it check the other 3 wheels for extra credit.

Assuming the wheel speed sensors were not the culprit, lets verify the Accumulator pump system. With the key in the OFF position, depress the brake pedal 40 times or so (this is to depressurize the system by using up stored hydraulic pressure in the accumulator,) afterwards turn the key to the ON position and listen to how long the accumulator pump runs, it should be around 40seconds ~ 1minute roughly (this gives a baseline of how hard the system needs to work to restore pressure in the accumulator tank.)

Once we get those out of the way we'll try some other stuff, but this should start you in the right direction. I normally would reccomend a Zero Point Calibration, but we're getting codes indicating other components rather than the system just randomly engaging/being overly aggressive with no DTCs; but you are welcome to do it as it won't hurt anything.

In regards to your air bubble idea, unless the system has been flushed/bled in the past or the brake system serviced by someone who did not have a Techstream... I wouldn't suspect any air if there is no leaks. To bleed the system properly requires a TIS Techstream scantool which mostly Dealerships have.