Intermittent Soft Brake Pedal - ABS Exercise Required

Here's what I know:

• 2012 Tundra Limited w/Supercharger - my daily driver
• ~200K Miles but still holding strong and running like a champ
• Brakes had been working fine, no issues at all
• I've put 20K miles on the truck in the two years I've owned it
• Free oil service from Toyota so far based on buying from dealer
  • Had some screaming pulley's when I bought it so I got a screaming good deal on the truck, then changed out the pulley's and solved the issue
• All three oil changes at Toyota included a brake assessment that was exactly the same all three times "you have around 5mm of material both front and back"...
• Took it to Les Schwab recently to have the LCA's switched out - they also checked the brakes and confirmed 5mm front and back
• I then started experiencing intermittent soft braking where I would drive and brake with no issues, then out of the blue, I'd press on the brake pedal and the throw was about 3/4 deep compared to around 1/3 throw to engage the brakes normally
• This happened 5-10% of the time and when it happened I'd still have solid brakes, just way lower in the pedal throw
• Plenty of brake fluid, no leaks
• LS suggested swapping out the Master Cylinder after performing a visual inspection that also revealed no leaks and plenty of material
• After swapping out the MC a few days ago the brakes felt firmer and the issue appeared to have been solved
• But then on the way home from work it happened again - pedal almost to the floor
• Today on the way to work all was good with the brakes until I really got on it (supercharger needs some action, right?) and after heavy acceleration the pedal went to the floor again
• I could then recreate the issue buy really stepping on it then coasting a bit then applying the brakes
• Each time this happens I can "pump" the brakes back up and then they seem to work fine

Everything I've read makes it sound like brake booster issues would create a rigid pedal and not soft and not intermittently. I'm assuming my driving habits are having some effect, but before I take it back to LS I'd love to know if any of you have ever experienced this issue. Any help will be much appreciated.

Let me know if I've left something out, and thanks again.

JB

 

Vacuum leak?

 

I was thinking vacuum leak as well but I have no idea where to start as far as tracking it down.

You think it may be related to the vacuum hose that supplies vacuum to the brake booster? Kept thinking if there was a leak is it only leaking when I really get on it, otherwise it's fine? It's all the decent braking that's throwing me off and why it works fine 95% of the time.

Thanks for jumping in, appreciate the advice, definitely helps narrow down the possible culprits.

 

Sounds like a brake booster if the master cylinder has been addressed. My old Land Rover LR3 did a very similar thing. It would be fine, then suddenly the brake pedal would drop almost to the floor. Did it when it was cold, turns out it was full of water, which was messing with the diaphragm.

 

I'd spray brake cleaner around the booster hose if the idle changes you should be able to narrow it down. If not the booster would be my next focus.

 

Thanks you guys, appreciate the assist.

Took it back over to LS this morning, they now know that while their initial diagnosis made sense it didn't account for vacuum issues - which I totally believe is the problem now due to the acceleration test from yesterday along with your suggestions.

Hopefully it's the brake booster. If it's a persistent vacuum leak I'd assume the engine would perform differently but I could be wrong. Everything I've been reading makes it sound like my idle would be rough and the engine would sound different - engine sounds great, no change and is peppy and responsive.

Thanks again, I'll chime in once I get it back or we move to the next phase of figuring this out.

 

Ok, so, here's the skinny, and I think we're good! But, I'll walk you through it still.

Took the truck back to LS this morning, dropped off promptly at 8. By noon I'd heard nothing, gave them a call. Guy says, "oh ya, we've been working on it, swapped your old master cylinder back in and bled the system again." At this point I'm like, WTF, I never told you to put it back in, you should have called me first to let me know what you were doing. At any rate, they knew I was frustrated, just want to know what's up with my truck. They said they'd have someone call me back once they were back from lunch. 2 pm rolls around, I've heard nothing, I go to LS to find out what's up.

When I got there I was definitely ramped up but really just anxious to hear what happened and what the next steps are. I'll shorten this up a bit, here are the highlights:

• The tech that worked on it had 21 years experience, great guy, explained everything
• Said it's not the booster or a vacuum issue due to an ever-softening brake pedal - if the booster was failing, even from a vacuum leak, the pedal would be rock hard - mine is intermittently soft, check. He then also mentioned he was suspicious of the ABS, which I've read can be a finicky little turd from time to time, but he didn't tell me what his test drive might include
• He then mentioned he wanted to take it on another test drive, I said, go for it, enjoy the supercharger, in fact, please get after it because right after that is when you'll feel the brake failure
• I then sat in the waiting area listening to a fishing channel while using my phone to look for other solves, including this ABS lead
• Found a thread about it, said the ABS valves need to be exercised, best way to remedy an intermittent soft pedal is to find a gravel parking lot or road, get er up to speed, then slam on the brakes and get the ABS to engage - sounds like this fix works consistently, cool!
• Tech dude comes back from the test drive, first thing he says is, you definitely have a Supercharger, I said, yes, I do.
• Says he tried my technique of getting on the gas heaving then brake right after and you should feel the soft pedal - this worked, pedal was soft, perfect, he's doing exactly what I told him to do, I'm encouraged
• He then says he did the gravel ABS exercise, and you know what? He said it totally worked! After the gravel he went back to burning my premium fuel hot then jumping on the brakes - COULD NOT RECREATE THE SOFT PEDAL ISSUE
• I was so stoked, shook his hand, thanked him, and then he gave me back the money I'd spent on the new Master Cylinder along with the labor charge - and today's visit - FREE
• This Les Schwab is amazing, the one in Forest Grove, Oregon, couldn't be more impressed - in fact, every LS I've visited has been outstanding, but this elevated service along with refunding me for the unnecessary part swap test was above and beyond my expectations, well done!

I then drove the truck around for a bit before heading home and had no issues at all. Whew.

I'll keep this thread updated if something else comes up related to this issue.

The key is to slam on your brakes more often..... who would've thunk that was the solve, wow.

Thanks again for your support, helps a ton.

 

Woo hoo! Glad it worked out. I'll have to remember this ABS exercise.

 

This is crazy. I would need to exercise my abs as well. I have a slight soft pedal. My prius brake pedal feels tens times better then the tundra.

 

Glad it worked out, what a stand up place! Wish there were more like it.

 

This may well be the secret of fixing the soft pedal syndrome. I had a very competent shop go over mine. They bled multiple times, replaced the MS and finally said I need to take it to a Toyota dealer and maybe bleed with a techsteam operating the ABS. They are very honest and were perplexed that they could not fix it. The Toyota dealer I go to said the Techstream ABS actuation would not be the fix. My pads were about 50-60% and the adviser said that after replacing pads it always fixes the soft brakes even if there is a lot of pad left. They had a special for $199 front or back. Had them do both. The pedal was perfect nice and firm and I was happy but still could not figure how replacing pads would fix the issue and thought the tech must have some trick that they do. I'm not upset that they did the all the pads and rotors for $400 but suspect the tech likely stomped on the brakes as well to fix the soft pedal. He also had adjusted the E-brake to perfection so glad about that.

If stomping the pedal on gravel is the fix, you have uncovered a huge fix for soft brakes which it appears have affected many Tundras based on posts out here on the web.

Thanks for posting your findings!

 

Man, I really do hope this fix is legit and I'll definitely provide an update if it reoccurs. Went out and drove it for a bit this morning, excited to further test it, and experienced a very consistent brake throw with good grab - so far so good.

Regarding pads, I have around 5mm all the way around, so I asked the LS tech if changing them and essentially doubling the material would help to shorten the throw in general and especially when the "soft pedal" occurs. He said nope, that the brakes are essentially self adjusting and that 5mm is actually a decent amount of material. He further stated that he's seen Toyota trucks go 150k miles ++ on the same pads because, well, basically, these trucks are over engineered and badass.

Stoked to imagine Tundra drivers seeking out gravel to exercise the ABS, seems like more fun than exercise!

 

Agree with the pad thickness not being an issue and Dealer agreed. Dealer said they were'nt sure why but replacing pads seemed to cure the soft pedal problem. I suspect they may have been selling the pads along with a good stomp on the pedal on a gravel road.

 

I lived in Boise most of my life. Les Schwab was the best tire store in town. I am here in Birmingham and wish there was a Les Schwab around. I purchased my 2006 about two month ago. Come to find out I have exactly the same problem. I tried the dirt road method and did not get the same result as you. Maybe I need to head back to the PNW to get the same result as you. I am so frustrated because no one here can solve the problem.

 

Sorry to hear that, Starlifter141, hope you get it figured out soon. If all else fails you may want to try again and really get that ABS to kick in, it's worth a shot. LS told me that the ABS unit may be faulty and need to be replaced, but lucky the gravel road method did the trick. Good luck!

Btw, mine is still braking as it should, very pleased with the outcome. I've since had my rack and pinion go out and once again LS came through for me. Toyota wanted ~$6K to replace it + the PS pump. LS did it for a third of the cost and it's now smooth as silk and likely to go another 200K miles!

So glad I decided to get this Tundra. Even with a ton of miles on it and a few funky fixes it's still a pleasure to drive and I've got nothing but confidence when it comes to its reliability.

 

Wow! Fascinating solution. Good on LS to take care of you!

 

You weren't getting any ABS lights or anything besides when you were trying to get it to kick in? Sorry for the old reply.. I got the ol spongey

 

I need to try this with my Sequoia...I've always thought the brakes were soft, even after new pads, rotors, new fluid and system bleed. Will be looking for a gravel road or parking lot soon!

***just got back, believe or not, there is a noticeable difference, hoping other people will try this and report back...I have an 08 Sequoia, 240k miles.

 

Update...my rear calipers were original to the car, passed inspection but clearly they were inefficient at 240k miles...so I replaced them with Power Stop Z36 truck and tow calipers with pads and drilled and slotted rotors, wow! Should have done that before...completely different braking experience. I already had Power Stop drilled and slotted rotors and pads on the front. Both of the front calipers are OEM but new in the last two year.