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Sinking brake pedal

Discussion in '2nd Gen Tundras (2007-2013)' started by Trucker1214, Oct 17, 2019.

  1. Oct 17, 2019 at 1:50 PM
    #1
    Trucker1214

    Trucker1214 [OP] New Member

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    2010 Tundra 4wd extended crew cab 5.7L SR5
    I have a 2010 Tundra that has a mysterious brake problem that has been diagnosed as a defective ABS pump issue by the local mechanic. Before making this very expensive repair, I wanted to see if the problem could be related to anything else. The problem is the brake stops the vehicle, but then the pedal continues to depress to the floor unless they are slightly pumped.
    I first replaced the master cylinder, thinking this was the problem with no change. I then completely replaced all 4 brakes with a 3rd party brake kit as well as new hoses - with no changes. The mechanic bled the brakes, activated the ABS and did all the normal brake bleeding things- with no change in the pedal. The ABS light is not on and there are no error codes being generated, however, the mechanic believes it has to be a defective ABS pump since there is nothing left. Has anyone seen this or have any reason to think it is not a defective ABS? Thanks
     
  2. Oct 17, 2019 at 1:56 PM
    #2
    15whtrd

    15whtrd Mr. Blonde

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    Brake booster?
     
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  3. Oct 17, 2019 at 3:10 PM
    #3
    rebmo

    rebmo 2020 Crewmax Limited 4wd Silver/Black

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    Take it out on a dirt or gravel road and slam on brakes and get the abs activating a few times and see if the sinking pedal goes away.
     
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  4. Oct 18, 2019 at 9:28 AM
    #4
    Trucker1214

    Trucker1214 [OP] New Member

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    2010 Tundra 4wd extended crew cab 5.7L SR5
    Some follow up on the problem and suggestions. With engine off, after pushing the pedal a few times the brake pedal hardens up properly as expected. After turning on the engine, the pedal goes to the floor and the brakes stay squishy and never harden up as expected and push to the floor, yet do stop the truck. Disconnected the ABS module and still had the same problem. Took it out on a gravel road and slammed the brakes several times. The ABS did activate and seemed to work by bringing me to a straight stop, though it didn't make any apparent improvement in the brake pedal. (Not sure if ABS activation is supposed to sound so klunky). From what I know so far, squishy brakes means there is compressible air in the system. Since there is a new master cylinder and no apparent leaks and it has been repeatedly bled, I'm not clear on how a faulty ABS system or a faulty brake booster could let air in the system or cause the symptoms... or possibly it could it be something else? Any clarity that can be added to explain the likely problem is appreciated. Thanks!
     
  5. Oct 18, 2019 at 9:49 AM
    #5
    Kerch71

    Kerch71 Surgical Precision

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    ^^^ this. Sounds like the only thing that hasn't been addressed.
     
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  6. Oct 18, 2019 at 10:19 AM
    #6
    15whtrd

    15whtrd Mr. Blonde

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    So on my first GEN Sequoia I had a similar issue. After the dealer telling me it was the ABS I went with my gut and changed the master cylinder. That ended up being the ticket for me. My brake light would come on and the pedal would go to the floor but still stop fine. If I pumped the brake pedal it would rise and be firm but only for that braking period. I’m no master mechanic, but I do think it’s possible the brake booster would give you similar symptoms if it had a leak. It’s not introducing air to your fluid but bleeding off air, and possibly not giving you the boost. It’s also possible you got a faulty master cylinder. I say this because your symptoms sound similar to my master cylinder issue. It’s also the cheapest of all the other solutions LOL. And a few years ago I have read that it is not good practice to bleed your brakes beyond the typical stroke of the pedal during normal braking. It puts the master cylinder piston into an area that may chew up the seals when bleeding. Just a heads up. I stuck a 2x4 under the brake pedal when bleeding to avoid this.
     
    Last edited: Mar 19, 2021
  7. Oct 18, 2019 at 11:20 AM
    #7
    Ajkkane

    Ajkkane Old fart.

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    If I remember correctly I think a bad booster will have a hissing sound and the brake pedal will be rock hard, and the vehicle will be hard to stop. It’s been awhile, but I think those are the symptoms of a bad booster.
     
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  8. Oct 18, 2019 at 11:21 AM
    #8
    15whtrd

    15whtrd Mr. Blonde

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    I think I’m now leaning towards a faulty replaced master cylinder.
     
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  9. Oct 18, 2019 at 11:24 AM
    #9
    Ajkkane

    Ajkkane Old fart.

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    Sounds like a strong possibility, I would think the actuator would have little to do with pedal sinking to the floor.
     
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  10. Oct 18, 2019 at 11:27 AM
    #10
    15whtrd

    15whtrd Mr. Blonde

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    Are you talking about the ABS actuator?
     
  11. Oct 18, 2019 at 3:33 PM
    #11
    Dr_Al

    Dr_Al New Member

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    Since the master has already been replaced it's unlikely that the new and old ones are both bad. Squishy could mean air in the system or fluid getting around a seal. I'm not an expert but I believe the way the ABS unit works is it alternates between allowing and blocking hydraulic oil from reaching the brakes with a series of valves. Since there's only two lines from the master to the ABS unit (a front and rear) each one serves as both supply and return for the oil. If the master is doing it's job and you are applying the brakes there's no way fluid should be allowed to return. I think that would mean either oil is leaking out externally inside the ABS unit or your problem is somewhere else. If you are loosing fluid you will see the level drop.

    I would expect a bad ABS unit to either not keep the wheels from locking up or make you have to push harder on the brake pedal to stop. I think I would try bleeding the system once again since it's much cheaper than replacing the ABS unit. Maybe going to a different mechanic might be in order.
     
  12. Oct 18, 2019 at 3:56 PM
    #12
    MyFj08

    MyFj08 New Member

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    What type and brand of fluid are you using

    I had a similar problem with my wife's car
    And bleed the fluid out changing it to non synthetic

    And it solved the problem
     
  13. Oct 18, 2019 at 4:01 PM
    #13
    ajax1

    ajax1 New Member

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    I’d try a gravity bleed first starting at the rear to the front. if you see air coming out then that’s part the problem. On 80 series cruisers gravity bleeds work the best and I do them on all my other vehicles since it only takes one person and you don’t risk killing your new master.
    I’ve also seen master cylinder fail out of the box especially remanded and aftermarket.
    Did you use Toyota master brand new or one of there suppliers?
    Your symptoms point to air in line or bad master
     
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  14. Oct 18, 2019 at 4:19 PM
    #14
    Ajkkane

    Ajkkane Old fart.

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    Yes
     
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  15. Aug 28, 2020 at 12:52 PM
    #15
    JMoney

    JMoney New Member

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    This is classic of a failed brake booster. The tundras and sequoias have that issue when brake booster goes bad. You think it would stay firm if booster was bad but actually on those they get mushy. And pls don't be a retard a slam on your brakes as hard as you can when you have faulty brakes more than likely that will not fix your problem and you might kill your self when your brake booster completely fails. change master cylinder then change booster and make sure the clearances on the booster are correct. MUCH LOVE.
     
  16. Mar 19, 2021 at 4:51 AM
    #16
    Joe456

    Joe456 New Member

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    I have a 2012 tundra that has a pedal that goes to the floor when running and pumping the brakes make them any better. I had to slam on the brake to miss a deer and immediately after that, I noticed the brakes were squishy and basically going to the floor. I can here a "whooshing" sound when applying the brakes when the truck is running. When the truck is off, the pedal is hard as a rock. I checked the check valve and it's fine. I can't find any fluid leaks anywhere. I recorded depressing the brake while the truck is running to give an idea of what it's doing. I am thinking it's a bad booster. Thank you guys for any help.
     
  17. Mar 26, 2021 at 12:55 PM
    #17
    01tunder

    01tunder New Member

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    Hey I have a 01 tundra 2wd it doesn't have abs but it's doing the same thing.

    I noticed the e brake doesnt brake the car when on a slant.
    I also noticed the back wires under the frame that hold the brakes are loose kinda looping down.
     
  18. Mar 26, 2021 at 3:20 PM
    #18
    Tipsovr

    Tipsovr New Member

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    My 2012 does the exact same thing.
     
  19. Mar 26, 2021 at 4:28 PM
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    Joe456

    Joe456 New Member

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    I'm wondering if it could be the master cylinder. I can pump the brakes forever with it running and the brake pedal doesn't firm up a bit, I just hope it isn't and ABS issue. I may take it Toyota and get them to diagnose it.
     
  20. Mar 26, 2021 at 6:36 PM
    #20
    dd7751

    dd7751 New Member

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    Hi, I just had the master cylinder and brake booster replaced on my 2013 Tundra today. C1310 fault. $1279 in parts, $380 labor. The MC leaked; there was a solenoid fault on the booster, and those parts cannot be replaced without buying the entire booster. Ugh.
     
  21. May 3, 2022 at 5:43 PM
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    Jake1540

    Jake1540 New Member

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    I have a 2010 tundra that had the same problem with the brake going to the floor. What's strange is that if you turn the truck off and pump the brake, the pedal never got firm. I took it to the dealership and they said I had a code with the booster. The mechanic recommended that I change the booster as well as master cylinder. He said the master isn't a genuine part and is a rebuilt one. I agreed that for brakes, I didn't want to take a chance.

    After replacing the booster and master cylinder new Toyota parts, the booster code was gone. The dealer called me back and said the problem with the pedal going to floor was still there and ABS light was on and had a code.

    He told me that he checked the brakes, calipers, rotors, hubs, shoes, wheel sensors, and made sure the brakes were adjusted. The brakes were bled but he said the volume of fluid coming from the front wheels was very low. I went and wanted to feel the pedal myself and even with a new factor booster and master cylinder, when pumping brakes with truck off, the pedal still wouldn't get firm. With the truck running, the pedal goes to floor as it did before.

    He said that the ABS module/unit is the only thing left that it could be. He said the pedal isn't getting firm because the abs unit can't build pressure likely due to issues with the internals of the unit such as valves. I'm not sure what to do, it's another 2k they want but I don't want to just throw money until it's fixed. Does this sound legitimate? Thanks in advance.
     
    Last edited: May 3, 2022
  22. Sep 19, 2022 at 5:21 PM
    #22
    Nemesis

    Nemesis New Member

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    Any updates from you two?
    I just experienced the same problem this past Sunday. I didn't want to chance an accident so I had the Tundra towed to the house. Tow guy unloaded the Tundra and lo'behold the brakes were rock solid, again.

    What is going on?!!! So, I come here and read about others experiencing the same thing yet no updates/solutions. I did notice what may appear to be a leak in the right side rear passenger brake (see pic) but I'm not all that confident that's the culprit. My 2008 CrewMax has 120K on the clock and is primarily used for commuting and towing purposes (i.e. toyhauler, though haven't towed since 2014). When I experienced the brake issue I heard a distinct hissing and mushy sound and possibly a click here and there. Fluid levels are perfect. No leaks by the MC or Booster. Any thoughts? So weird and ANNOYING!

    PASSENGER REAR BRAKE.jpg
     
  23. Oct 12, 2022 at 8:06 AM
    #23
    uk1cats

    uk1cats New Member

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    I had the same issue with my 2007 Tundra Limited Crewmax. No leaks and fluid levels were fine. Thought it was a bad Brake Booster as I only had the VSC light flashing & Trac Control light Solid (and per the Code matrix attached. It was either that or a blown 4wd fuse but the fuse checked out okay). So bought a new Brake Booster and also went ahead and put a new Master Cylinder on while I was in there. Still had the issue with soft brakes and the Trac Control/VSC lights on afterwards. I had put new brakes (rotors & pads) on all around last year so knew it couldn't be that but rechecked them anyways with no issues found. Only thing left from forums was the ABS unit. Ordered one for around $500 and changed it out. Bled the brakes, drove in the neighborhood and pumped then slammed the brakes a couple of times to activate the ABS and Boom solid brakes again. The lights immediately went off as soon as I had put the new ABS unit in and turned the ignition on but the ABS light came on Solid. After the hard stop to activate the ABS Unit the ABS light went off. Hope this helps!

    Tundra Indicator Lights matrix.jpg
     
    Last edited: Oct 12, 2022
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  24. Nov 3, 2022 at 4:30 PM
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    Nemesis

    Nemesis New Member

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    In my case, my CM is not displaying any VSC or TC lights whatsoever. And I don't have any CEL on either.

    BTW, today on our way to the beach the brakes went mushy again. Scary feeling. Thank God for the sequential gear shifter. Helped reduce speed so I didn't have to rely heavily on the brakes.

    As much as I'd hate to do it, I'll have to take it to the stealership. Hopefully, the brakes will remain mushy so they can witness it for themselves. Last time when the tow guy unloaded the Tundra the brakes felt solid again. Pissed me off.
     
    Last edited: Nov 3, 2022
  25. Jan 1, 2023 at 6:17 PM
    #25
    shamrock246

    shamrock246 New Member

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    Is there any info on how the booster is causing a soft pedal? Internal failure of some sort? Is there a certain year range this effects?
     
  26. Sep 30, 2023 at 3:17 AM
    #26
    ToyotaSequoia

    ToyotaSequoia New Member

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    Since the brake booster has a vacuum hose going to intake manifold, and power steering air control valve also has a hose going into the intake manifold, could a bad power steering air control valve cause brakes to not have proper vacuum to be firm, witch results in soft/squishy brakes?
    Please tell me im right!!!
     

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