Poor Brake Performance After TBU
 

Hey guys, I just did a TBU last weekend, but the brake pedal travel was pretty bad, almost to the floor. I got it into a local shop that got good reviews, and they're telling me that I might have gotten air into the ABS system when I did my flush, and that they'll need to bleed the ABS and adjust the brake push rod. They're quoting all of this at several hours over the initial quote for a brake system flush ($411 vs $140). Now granted, I haven't don't a brake bleed/flush since I was about 14, so I'll be the first to admit I probably did a sub-par job. But this seems a little steep for the work they're talking about doing.

Am I getting had?

Make sure your rear brake drums are adjusted properly. It's easy enough to do yourself with a flat blade screw driver.

That said, I had air in my ABS pump and I was able to get the air out by doing a ton of skids down a dirt road. The skids enabled the ABS pumps and pushed the air bubbles into the lines. After that I bled the brakes as usual and all was well.

Tbu mod has a reputaion for spongy pedal. Some have bled the brakes with engine running and have had good results.

watch @mtbtim video YouTube

How many times did you bleed it? Did you start from the furthest wheel away from the master cylinder? Did the shop try to bleed the brakes themselves before coming to the ABS conclusion?

Just hookup a clear line to your bleeder valve and the other end inside of a water bottle with some brake fluid at the bottom to prevent sucking air in. Go around each caliper and drum and bleed them. Have someone press the brake pedal to the floor before you break the bolt loose. Have them pump 5 times or keep pumping untill there are no bubbles. Even micro bubbles. If need be put a zip tie around the clear hose where it attaches to the bleeder to create a tight seal. I put 3 bottles of brake fluid through my truck before all my micro bubbles were out. While doing this ensure that your brake fluid never empties. Always top it off as needed to ensure that no new air is introduced into the system. I highly doubt you've got what they said. After completed pedal should be firmer than it probably is now but will never (in my experience) be as firm as it was with stock calipers. However offroading I've experienced better performance with the TBU as it is less sensitive and you learn how much the pedal needs to be pressed in order to receive a certain type of braking. Adjusting the pedal may be a good idea. I'm going to look Into that

OP, when you bled the brakes, did you starve the reservoir of brake fluid at all?

ive read that some cars equipped with ABS need to have the reservoir topped off at all times while doing a bleed job so you dont get any air in the ABS unit. if you dont do this, air gets in the ABS unit and it now has to be bled. from what i understand, its generally harder to bleed those rather than all 4 corners.

someone please correct me if im wrong, but id like to learn as much as i can about these issues (this isnt the first time ive seen a thread like this regarding the TBU). i plan to do this upgrade some point down the line.

I did 2 cycles, starting at rear passenger, then rear driver, then front passenger, then front driver.

Shop said they did one bleed and then pumped ABS system using the computer. Said they'll have to do at least one more bleed and adjust the rear brake, and probably adjust the brake push rod.

He mentioned that if that doesn't work, they've seen this job done before and sometimes it requires upgrading the master cylinder. THAT sounds like a load of crock, but I'll defer to you guys who have done this before and wait til it comes to that to call them out. Nothing I've read about this upgrade mentions needing to swap the master cylinder--but perhaps I just missed it.

Yeah this is my fear--I let it get pretty low at one point during the first cycle, which is why I ended up going around a second time (and saw more air in the second cycle).

The shop is priming you with all this bogus talk of new master cylinder etc. I bet that after the intial brake bleed when they couldn't fix the problem they just started grabbing at causes.Infact they are clueless.

You do not need to upgrade the master cylinder, I run a stock one with the 231mm upgrade. Stops just fine. You could try bleeding a couple more times just to make sure that all air is out of the lines, on the plus side you are getting rid of the old brake fluid which should be done anyways. I have no experience with bleeding the abs, but I do know it took me a few bleeds to get a firm pedal.

You probably still have air in your brake lines if you let the reservoir get that low. I recommend getting speed bleeders and re-bleeding your entire brake system. Speed bleeders will ensure that you can bleed the brakes by yourself without getting any air back in the system a lot faster. Yes, putting a clear hose on the bleeder nipple and submerging it in a bottle of brake fluid will work but it's more time consuming in my opinion. Also, bleed the brakes with the key on or engine on and check your reservoir level frequently. Rear drums can be adjusted by repeatedly cycling the parking brake level assuming your bell cranks aren't seized and your drum shoe adjusters are functioning properly. If you decide to get speed bleeders you'll need front speed bleeders for a 2006 Tundra and rear speed bleeders for your year 4Runner.

Sounds like you still have air in the lines. You can try speed bleeders but I haven't had much luck with them. I use a pressure bleeder, works like a charm and bleeds brakes fast.

How does the pedal feel with engine off and all vacuum out of the booster? Should be rock hard.

Only 2 ways I ever bleed brakes-

1. With 2 people, pump 3, crack nipple, hold, close refill master. Wash rinse repeat.

2. Pressure bleeder (I use many diff DOT fluids so I never fill the pressure bleeder), just fill up master, put on adapter cap, pump can to 10 psi, and start bleeding. Always check master for fluid levels.

I don't have the tbu yet, but just flushed my brakes and pedal is perfect. Also like many said before, adjust your drums as well.

If you ran the master cylinder dry you might also have air in the master cylinder, I just installed extended stainless brake lines and read about bleeding the brake system in my factory service Manual. I can take a picture of the page when I get home tonight if you would like.

Could probably get a picture of how to bleed the abs system as well. Let me know

Good luck! I've been fitting this issue for over 2 years, and now just deal with it. It's actually the one upgrade I wish I would never have done. Now I double pump the brakes if needed.

I've read about this happening a lot on 01-02 models since that's when Toyota changed to the electric ABS master cylinder brake booster unit. I've seen one fix on this, and that requires to dealer to bleed the ABS and booster. Which is the only thing I haven't done...yet.

Mike

I have had problems as well after the TBU over a year ago,but in my case it's an occasional soft brake pedal,the truck will stop but the travel is excessive and it's abit scary at times,tried the hard stops to get ABS going a couple of times with no improvement,I've heard of others with the same problem...I've got a 2000 SR5