Brake Issue

[Moist]

Moist,
Not that we've seen. We haven't been able to think of anyway the system would have a leak that would be causing this issue. Everytime we have messed with the brake system in its entirety, we bleed the whole system with a vacuum.
The rear calipers didn't seem to be an issue when we last checked them compared to the front. It appeared that the front calipers pistons were hung up for lack of a better term.

How hard is this truck driven? Overheating will do something like that. That's how my old brakes went out.

Having to pump the brakes at a standstill is really weird to me. Even my old set with rust welding brakes wouldn't do that. It makes me suspect something wrong with however they pressurize. (Reminds me of how some aircraft control surfaces "Sag" when hydraulics are lost)
When you get on the brakes can you hear the motor/petal buzzing on fairly regular intervals? Should be a steady low buzzing that lasts for like five seconds - stops - and then buzzes again if need be. The pedal might vibrate too when it happens. (If you need an example of the sound I'll record it and post it here)

EDIT1: I have a vague understanding of the actual hydraulic systems behind these brakes, but I figure the more info the better. My old motor buzzed very weakly and would cut out. And that set of brakes had the petal go about 50-75% to the floor before they caught.

 

[Gabbagoul]

The truck isn't driven hard, learned early on when you're hard on your own stuff the only person who ends up losing in the end is you. Hardest driving I've done to date with it is driven downstate to pick up a trailer 5x9 loaded and back up. Rpms buzzed along around 2.5-3k. The buzzing sound of the motor turning on, I have no frame of reference, but can listen tomorrow and report back.

 

[SocalSam]

Hey all,
Not to hijack the thread, but I'm also having a brake issue and I'm hoping you guys can help me out. They were feeling squishy like there was air in the line. Bled the system, rebuilt the piston in the master cylinder and things got better for a while. Replaced the front calipers with new ones and the flexible lines on all four corners have been switched to stainless braided lines. The brake pedal travels a while before the vehicle stops and even when it does, I'll have to reapply/pump the brake again to keep it stopped otherwise it will break loose and roll forward. Again, I apologize if this is hijacking the current thread but I'm running out of options. Thanks all in advance.

Did you bleed valve block? Press brake pedal and crack lines to and from block. Then go for a drive and on an open and safe road, trigger ABS and traction events. Repeat as necessary. If this does not work, then there is a chance accumulator is not holding pressure and will need to be replaced.

 

[Gabbagoul]

So I just got back from taking it for a drive and listening for some of the things you guys have told me. I don't know if my hearing is just that terrible or what but I'm not hearing any pump kick on.
Socal, in regards to the valve block, can you give me a bit more insight? I'm lost on what that is.

 

[AuSeeker]

So I just got back from taking it for a drive and listening for some of the things you guys have told me. I don't know if my hearing is just that terrible or what but I'm not hearing any pump kick on.
Socal, in regards to the valve block, can you give me a bit more insight? I'm lost on what that is.

You don't have to drive to get the pump to kick on, try this without turning the ignition on, pump the brake pedal about 20 times, this will use all of the pressure the pump has built up, then while someone listens under the hood and close to the master cylinder simply turn the ignition on like you're going to start the engine but don't turn it to the start position, if the motor for the pump is working at all you will hear it kick on and run off and on several times until the pressure is restored, there's no need to start the engine or drive it to get the motor to kick on.

My guess is the motor is kicking on and the pump is building pressure because if it isn't and the pressure is depleted the "brake" light on the instrument panel will light up and a alarm will activate until the pressure is restored, also the brake pedal will go way down and be rock hard with very little braking action, unless you really push extremely hard and even still the brakes have a hard time slowing the vehicle must less stopping it effectively, my ABS/master cylinder failed and the only way I could slow down and eventually stop was to downshift to slow down and then using both my brake pedal and parking to come to a full stop.

The way the system works is the motor and pump provides pressure for the ABS system to work and also give you the "power brakes", without that pressure it's very hard to stop, i.e. read the last paragraph again!

When the system is working properly, the pressure drops every time you depress the brake pedal until it gets below the pressure threshold setting and then the motor kicks on and the pump builds up the pressure again, it's usually about every 3 to 5 depressions of the brake pedal for that pressure to drop low enough to have the pump kick on.

Did you do all the work on the brakes you described or did you pay a mechanic to do the work?

 

[MikeinNH67]

As mentioned, the pump must be working or it would be hard as a rock at some point in the travel. Did you do the actual brake bleeding procedure listed in the "stickies" section? Part of the procedure has the ignition on with brake depressed slightly so the motor pushes fluid and air out. Here is the link.

https://www.toyota-4runner.org/4th-...-bleeding-w-abs-w-o-sst-tool.html#post1422320

 

[Moist]

You don't have to drive to get the pump to kick on, try this without turning the ignition on, pump the brake pedal about 20 times, this will use all of the pressure the pump has built up, then while someone listens under the hood and close to the master cylinder simply turn the ignition on like you're going to start the engine but don't turn it to the start position, if the motor for the pump is working at all you will hear it kick on and run off and on several times until the pressure is restored, there's no need to start the engine or drive it to get the motor to kick on.

My guess is the motor is kicking on and the pump is building pressure because if it isn't and the pressure is depleted the "brake" light on the instrument panel will light up and a alarm will activate until the pressure is restored, also the brake pedal will go way down and be rock hard with very little braking action, unless you really push extremely hard and even still the brakes have a hard time slowing the vehicle must less stopping it effectively, my ABS/master cylinder failed and the only way I could slow down and eventually stop was to downshift to slow down and then using both my brake pedal and parking to come to a full stop.

The way the system works is the motor and pump provides pressure for the ABS system to work and also give you the "power brakes", without that pressure it's very hard to stop, i.e. read the last paragraph again!

When the system is working properly, the pressure drops every time you depress the brake pedal until it gets below the pressure threshold setting and then the motor kicks on and the pump builds up the pressure again, it's usually about every 3 to 5 depressions of the brake pedal for that pressure to drop low enough to have the pump kick on.

Did you do all the work on the brakes you described or did you pay a mechanic to do the work?

After my classes today I'll grab a clip of it inside and outside the car and attach it to this post to get the sound
Edit: (whoops quoted wrong post)

 

[Gabbagoul]

Haven't forgot about you guys. Been having issues logging in lately. Work has been crazy so my next set of days off I'll go through and try what you guys have posted and see if that remedies the issue and report back my findings.

 

[Ralph Blake]

After reading about people having many brake problems after doing their own replacment work for many years, and having to again do it over and having to again replace damaged parts.

Myself think if you take your 4runners to a shop that has done a lot of 4runner brake work, you might be both ahead on the brake job also if things are not perfect you have some where to get it perfect.

Sure it's costly but sometimes it's best to spend the money.

 

[Gabbagoul]

So I was able to check today as AuSeeker described. The motor and pump are turning on. Between a buddy and I are the ones wrenching on the 4runner since I've owned it. Next step from here is im going to follow the link to bleeding them without the SST and if that doesn't work try taking it to the local dealership. Only reason I'm hesitant to is because I've had ok dealings with them in getting parts otherwise they've been a bit of a pain to deal with.

 

[SocalSam]

After reading about people having many brake problems after doing their own replacment work for many years, and having to again do it over and having to again replace damaged parts.

Myself think if you take your 4runners to a shop that has done a lot of 4runner brake work, you might be both ahead on the brake job also if things are not perfect you have some where to get it perfect.

Sure it's costly but sometimes it's best to spend the money.

I do not disagree. New OEM parts are super expensive which increases the risk for shade tree mechanics. However after fixing mine for super cheap ($60), our hydroboost system is a non-concern for me. I cross referenced pump and accumulator and pulled them from a 2003 Lexus GS300.

 

[Gabbagoul]

I took my 4runner to the local dealer to have them bleed the brakes with their diagnostic tool. They were no help. Said they couldn't bleed them and I had issues with my rear hardlines, so back to the drawing board.