Occasional loss of braking - Toyota Tundra

Reply

  #1  
Old 07-12-19, 09:50 AM
Member
Thread Starter
Join Date: Mar 2009
Location: Northern Virginia
Posts: 3,892
Received 1 Vote on 1 Post
Occasional loss of braking - Toyota Tundra

I have a 2004 Toyota Tundra, and for the past couple years sometimes the pedal will travel freely to the floor and I completely lose braking ability. When I lift off the pedal and press again, braking is restored. It only happens one out of 100 times pressing the pedal, but it is very unnerving when it does (I've nearly rear ended someone). I had the lines flushed with BG cleaner a month ago, but the problem persists. Could this be caused by a leaking seal inside the brake booster? If so, why would it only happen once out of every hundred times then work fine after releasing and pressing again?

I just read online about another Tundra owner (albeit a newer model) having a similar issue. Bled the brakes multiple times, replace the booster, wheel bearings, etc. and still had a problem. Turned out being sticky valves in the ABS unit. The suggestion was to accelerate to a moderate speed then slam on the brakes repeatedly to engage the ABS and exercise the valves to free them up. Or do this on a dirt road at slower speed. Thoughts?

If it makes any difference, I want to say it typically happens at very low speeds as I'm coming to a stop. Does that rule out a faulty ABS modulator? Would a bad brake booster check valve cause this to happen?
 

Last edited by mossman; 07-12-19 at 10:12 AM.
Sponsored Links
  #2  
Old 07-12-19, 12:39 PM
Member
Join Date: Aug 2015
Location: USA
Posts: 475
Received 6 Votes on 6 Posts
would probably suspect a bad master cylinder , the booster would not result in the pedal going to the floor not really familiar with bg cleaner but many do recommend replacing the old brake fluid out as maintenance but I wouldnt ever expect that alone to fix a problem.
 
  #3  
Old 07-12-19, 12:54 PM
Member
Thread Starter
Join Date: Mar 2009
Location: Northern Virginia
Posts: 3,892
Received 1 Vote on 1 Post
Are the correct assumptions correct?

- Bad booster would result in stiff pedal (not a soft one that abruptly and intermittently goes to the floor)
- Bad check valve, same result as bad booster
- ABS - would only be an issue with hard braking, not normal braking

This leaves air in the system somewhere and/or a possible leak or a failing MC.
 
  #4  
Old 07-12-19, 01:22 PM
Marq1's Avatar
Member
Join Date: Sep 2016
Location: USA MI
Posts: 4,334
Received 94 Votes on 85 Posts
Bad booster would result in hard, un-assisted braking.

Bad MC would result in no braking, fluid leaking past seals and pedal going to floor but should not be just occasionally!

ABS would not have anything to do with normal braking, it only activates during hard/panic stops and would never cause pedal to go to floor or hard braking.

Air in system would give constant spongy feel!

I would also say it's MC!
 
  #5  
Old 07-12-19, 01:41 PM
Member
Join Date: Aug 2015
Location: USA
Posts: 475
Received 6 Votes on 6 Posts
the booster does not cause the pedal to go to the floor so no its not correct, pump up your brakes several times with your engine off your pedal should get higher as you lose the vacuum stored in the booster then with your foot still on the brake start the engine and your pedal will drop cause the vacuum is assisting to help you push the pedal down further than you could without it, all the check valve does is lock vacuum in the booster so you will still have power brakes to assist in stopping even if you do not have engine vacuum like if your engine died.
 
  #6  
Old 07-22-19, 06:08 AM
Member
Thread Starter
Join Date: Mar 2009
Location: Northern Virginia
Posts: 3,892
Received 1 Vote on 1 Post
I took a trip to the beach last week and it was getting worse, so I stopped at the auto parts store and picked up a master cylinder and replaced it when I got to my destination. The issue didn't occur at all for the entire 250 mile return trip home, then resurfaced as I was pulling into my driveway. So I guess it's an issue with the ABS? Stuck outlet/dump valve? Can these valves be replaced individually or would the entire unit need to be replaced? From what I've read, this isn't a DIY job?
 

Last edited by mossman; 07-22-19 at 08:31 AM.
  #7  
Old 08-27-19, 01:18 PM
Member
Thread Starter
Join Date: Mar 2009
Location: Northern Virginia
Posts: 3,892
Received 1 Vote on 1 Post
Just a quick update: I took the truck on a gravel road and slammed on the brakes several times to exercise the ABS. That was three weeks ago and I haven't had any issues since.
 
Reply

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Thread Tools
Search this Thread
Display Modes
 
Ask a Question
Question Title:
Description: