Random Soft Brake Petal

smokey7722

smokey7722

New member
My '05 has been running great however yesterday I noticed while driving that when I hit the brakes it felt pretty soft and I had to push the petal down much further than usual. This seemed to be pretty random though as certain stop signs/lights I would stop fine, others I would have to jam it down pretty hard to stop the vehicle.

I haven't pulled the tire yet to inspect further but visually I don't see anything out of the ordinary like leaking anywhere or low brake fluid. There is a hose thats near the frame by the front left tire thats not really attached to anything (it just abruptly ends with a solid cap as well) thats clanging a bit as it isn't secured though I can't figure out what its for (it ends near the end of the tire and runs forward on the frame where it crosses over and underneath the engine). I'm going to try to get a photo of it this morning as you can see it through the wheel well.

Years ago one of the pistons seized in the drivers side caliper which I replaced the entire unit at the time. I've got fairly new pads and rotors installed as well.

Other then grabbing the photo of that mystery hose thats not secured - any recommendations for initial diagnosis? I called my local shop to check their schedule in case this is something bigger than what I have time or skill to handle but they can't see it until at least Monday so I figured in the meantime I would reach out here.

I've got a scantool attached and theres been no codes at this point either.
 
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OK, 100+ views and no responses.
I'm moving this to the Problems section where you might get more response.

As for the mystery hose, instead of taking a pic for us to guess at, why don't you trace the loose end back to it's source, and then get back to us.
 
smokey7722 said:
My '05 has been running great however yesterday I noticed while driving that when I hit the brakes it felt pretty soft and I had to push the petal down much further than usual. This seemed to be pretty random though as certain stop signs/lights I would stop fine, others I would have to jam it down pretty hard to stop the vehicle.

I haven't pulled the tire yet to inspect further but visually I don't see anything out of the ordinary like leaking anywhere or low brake fluid. There is a hose thats near the frame by the front left tire thats not really attached to anything (it just abruptly ends with a solid cap as well) thats clanging a bit as it isn't secured though I can't figure out what its for (it ends near the end of the tire and runs forward on the frame where it crosses over and underneath the engine). I'm going to try to get a photo of it this morning as you can see it through the wheel well.

Years ago one of the pistons seized in the drivers side caliper which I replaced the entire unit at the time. I've got fairly new pads and rotors installed as well.

Other then grabbing the photo of that mystery hose thats not secured - any recommendations for initial diagnosis? I called my local shop to check their schedule in case this is something bigger than what I have time or skill to handle but they can't see it until at least Monday so I figured in the meantime I would reach out here.

I've got a scantool attached and theres been no codes at this point either.
Click to expand...
soft, or low pedal?


but, unless there is a fluid leak, these types of problems usually turn out to be a bad MC/abs unit. unfortunately, they are a complete unit, and can be quite costly to replace.
 
nevada said:
soft, or low pedal?


but, unless there is a fluid leak, these types of problems usually turn out to be a bad MC/abs unit. unfortunately, they are a complete unit, and can be quite costly to replace.
Click to expand...

No leaking from what I could tell anywhere and fluid levels haven't changed at all (when looking at the reservoir). I looked it up and it was about $1200 on average for a MC/abs unit. Not sure if theres value in having a shop take a look at it vs just buying the replacement unit and installing myself though at this point as it seems pretty cut and dry.
 
Is there a chance this could be the brake booster instead of the MC? I tried depressing the petal and starting the truck and the petal did move quite a bit which is what the threads say would indicate the booster is functioning ok? Is there another test I could perform to try to determine which it could be?
 
smokey7722 said:
Is there a chance this could be the brake booster instead of the MC? I tried depressing the petal and starting the truck and the petal did move quite a bit which is what the threads say would indicate the booster is functioning ok? Is there another test I could perform to try to determine which it could be?
Click to expand...
the booster/mc/abs are all one unit. these will not respond like a normal vacuum booster.
 
smokey7722 said:
Partznet shows them as individual components which is why I had asked. If they list it right, MC is 47025-60081 at $1222 and the Motor/Pump (Brake Booster) is 47960-30030 at $1184. Not sure if this link will work but this is where I was looking:

Hydraulic System for 2005 Toyota 4Runner | Conicelli Toyota of Conshohock
Click to expand...
unless im reading that wrong, the "actuator assembly" 47050-35030 lists everything, MC included for $1945. whereas JUST the MC is $1222.


a low pedal would likely be the MC bypassing internally. but you have to split both pieces apart to change that, makes sense to just change the entire thing at once. tons of these have had the booster portion fail though.
 
nevada said:
unless im reading that wrong, the "actuator assembly" 47050-35030 lists everything, MC included for $1945. whereas JUST the MC is $1222.


a low pedal would likely be the MC bypassing internally. but you have to split both pieces apart to change that, makes sense to just change the entire thing at once. tons of these have had the booster portion fail though.
Click to expand...

Correct that part does include both. I wasn't sure if getting separate was the way to go (if one of them doesn't fail as often as the other and it wasn't worth it). Good thing I have no interest in getting rid of this thing as this is an expensive repair.
 
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smokey7722 said:
My '05 has been running great however yesterday I noticed while driving that when I hit the brakes it felt pretty soft and I had to push the petal down much further than usual. This seemed to be pretty random though as certain stop signs/lights I would stop fine, others I would have to jam it down pretty hard to stop the vehicle.

I haven't pulled the tire yet to inspect further but visually I don't see anything out of the ordinary like leaking anywhere or low brake fluid. There is a hose thats near the frame by the front left tire thats not really attached to anything (it just abruptly ends with a solid cap as well) thats clanging a bit as it isn't secured though I can't figure out what its for (it ends near the end of the tire and runs forward on the frame where it crosses over and underneath the engine). I'm going to try to get a photo of it this morning as you can see it through the wheel well.

Years ago one of the pistons seized in the drivers side caliper which I replaced the entire unit at the time. I've got fairly new pads and rotors installed as well.

Other then grabbing the photo of that mystery hose thats not secured - any recommendations for initial diagnosis? I called my local shop to check their schedule in case this is something bigger than what I have time or skill to handle but they can't see it until at least Monday so I figured in the meantime I would reach out here.

I've got a scantool attached and theres been no codes at this point either.
Click to expand...

I see all this discussion about ABS modules without a single diagnostic data point, ignore all of this.

1) Disassemble brakes and check caliper pistons and any sliding components. Toyota caliper design is garbage and the pistons will sieze over, and over, and over, and over.

2) Any shimmy? Severe warpage of the rotor could force a piston back into its bore enough that first brake pedal press needs to take up that distance resulting in chronic low pedal.

3) Do you ever get TCS/ABS going off seemingly for no reason? Have you replaced any wheel bearing/hub assemblies? Intermittent signal from ABS reluctor ring could result in momentary false triggering of ABS or TCS. Could possibly be imperceptible depending on conditions though I would expect it to become obvious as the intermittent signal is usually due to reluctor ring contamination from imminent catastrophic wheel bearing failure. The front wheel bearings on this design will not make the classic failure noises and you may not realize the bearing is failing until it has reached the catastrophic point.

4) Do not just go buy some ABS module and test it. Download the service manual, there are links to it, it's free. Find the pinpoint tests for low brake pedal and rule out from there. I haven't put an ABS module on a 4th generation 4runner yet. I more expect these problems with Highlander.
 
geurillawarfare said:
I see all this discussion about ABS modules without a single diagnostic data point, ignore all of this.
Click to expand...

Thanks for the feedback/direction. I have not ordered anything yet as I am trying to confirm the cause as much as possible before I spent this type of money.

geurillawarfare said:
1) Disassemble brakes and check caliper pistons and any sliding components. Toyota caliper design is garbage and the pistons will sieze over, and over, and over, and over.
Click to expand...


Thats on my plate this morning. I have replaced the drivers side caliper with a re-man'ed one years ago due to one of the pistons seizing but it never caused a soft brake petal like this.

geurillawarfare said:
2) Any shimmy? Severe warpage of the rotor could force a piston back into its bore enough that first brake pedal press needs to take up that distance resulting in chronic low pedal.
Click to expand...

No shimmy at all.

geurillawarfare said:
3) Do you ever get TCS/ABS going off seemingly for no reason? Have you replaced any wheel bearing/hub assemblies? Intermittent signal from ABS reluctor ring could result in momentary false triggering of ABS or TCS. Could possibly be imperceptible depending on conditions though I would expect it to become obvious as the intermittent signal is usually due to reluctor ring contamination from imminent catastrophic wheel bearing failure. The front wheel bearings on this design will not make the classic failure noises and you may not realize the bearing is failing until it has reached the catastrophic point.
Click to expand...

TCS/ABS hasn't gone off at all with this issue.

geurillawarfare said:
4) Do not just go buy some ABS module and test it. Download the service manual, there are links to it, it's free. Find the pinpoint tests for low brake pedal and rule out from there. I haven't put an ABS module on a 4th generation 4runner yet. I more expect these problems with Highlander.
Click to expand...

I don't have a tester to do this myself which is what the service manuals refer to using. I'm waiting on a programmer out here to call me back to see when he has some time.
 
So I finally got under it today and theres definitely a few things I noticed.

- Passenger side has grease ALL over so it looks like the cv boot on that side.
- Passenger side caliper pistons move nicely when I manually tested
- Driver side lug nuts SOMEHOW were all loose - thankfully i stopped driving it or that would have ended horribly at some point.
- Driver side caliper pistons barely moved when I manually tested.

Interesting enough when I put it all back together and took it around the block, the brakes seemed fine now. So maybe its the driver side caliper thats shot again (I replaced it years ago from one of the pistons seizing then)? By manually playing with it maybe somehow that stopped this issue? I was planning on towing it into a local shop in the morning who offered to diagnose it for an hour of shop time labor though at this point the brakes seem ok so the best I can have them do is confirm that the caliper and cv need to be addressed?
 
OEM vs used? when same warranty

47050-35030 part needs to be ordered for my car.
New $1900, used $999
06 4runner SR5 with 135k. Planning to keep it for a long time.

First time ever posting in a forum. I hope I am doing it right. I need help.

Thank you, somebody
 
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