Bleeding hydro boost brakes and letting pump do the work? (2nd Gen Taco)

Hi new member here...

A family member gave me permission to wrench in there garage for a day. So I will be using this opportunity to do as much service work as possible, including replacing the brake fluid, which ive done in the past on other cars using techstream or by vacuum (don't have access to those fancy things anymore). Also not really a fan of vac hand pumps either...

Anyways, I was doing some research on here and a 4runner forum, and I came across people bleeding hydroboost style braking systems, w/o using a scan tool, and w/o any buddy's around to help them. Which is a good option for me because my techstream subscription expired awhile ago, and there aren't any buddies around to help me.

So the procedure is something like this, they would crack open a rear bleeder,clear tube into a one man bleeder device, KOEO, and press the brakes slightly to have the abs pump do all the work. I'm very interested in this method, but have a few questions about it.

1. To those who have tried this method, how were the results?

2. Do you think I could use this method on the front brakes as well? I'm assuming not?

3. If this method does not work on the fronts. Do you think for the fronts, I can get decent results using the pressing/hold technique, if I use a pedal depressor instead of a buddy for the hold part?

4. In what order would you bleed a hydro boost style system?

Much Appreciated.

 

Our trucks don't have hydroboost, they have an electro hydaulic pump (TRD offroad models). Hydroboost is something typically used on diesels since they don't have vacuum systems. If you have the electro hydraulic boost master, your method will work and I have used it with great results.

• Fill brake reservoir to max, turn key to "on" so it kicks on the pump.
• Place 2x4 between seat and brake pedal, jam brake pedal to the floor by wedging your wood in the gap (teehee)
• Go about your bleeding process, the pump will kick on and off as required to maintain pressure. Go in short intervals, don't let the pressure die down too far, and keep an eye on your reservoir level through every several cycles of the bleeder valve.
• Start with the caliper closes to the reservoir (drivers front) and work your way back to the farthest away.
• Have about 2 bottles of 32oz brake fluid on hand if planning to do a full flush.

 

I would be exhausted crawling in and out from under the truck!

I like my vacuum bleeder just fine.

 

easy fix to that!

 

Then it would be letting the lift down to check the fluid if I used a ladder I would manage to fall off.

Then years ago when I had the extra money(88-90) lifts were still very expensive compared to today

 

Your a life saver. I have been searching close to three days trying to find that exact info! I should have tried other key words besides , tacoma electro pump bleeding/4x4/bleeding/electric hydro pump/abs pump ect... From that article now I know the results are good, and it can be done on the fronts too. Thanks again!

Thanks for the clarification on the hydroboost. Yes my Tacoma does have the electro hydraulic boost master cylinder. It's also known as the one that keeps buzzzzing and never shuts up lol.

Your method is slightly different from the link whatstcp posted. And I like yours better because of the 2x4, cause I don't have to keep going inside to press the brakes. But I was wondering about the bleeding order. Your method is to do the fronts first while the other thread states to do the rears first.

Correct me if im wrong, is the reason you do the fronts first in your method is because the act of placing a 2x4 to the floor creates an initial manual pressure build up, that needs to be bled off from the fronts?

And in the thread link whatstcp posted. The op of that thread recommended to do the rears first. Do you think the reason he does it that way, is because he plans on going inside and doing a light manual pressing of the brakes to kick on the pump when he needs it, and there was no initial manual pressure build up that has to be relieved to the fronts first?

Or am I just over thinking it haha

 

I am under the impression that it doesn't make any difference, but maybe I'm wrong. All 4 lines are separate coming out of the module so it wouldn't appear to be affected by which one you bleed first, I start in the front simply because I was up there checking the fluid level. In the old days where the brake lines were shared with no ABS modules, you'd want to start with the one farthest away because you save some bleeding time and prevent air from a shared line from backfeeding into one you just bled. If you look on the back of tacoma axle, you'll see that each rear brake has a separate line coming from the frame and down to the axle tube where it converts from the soft line to the hard line.

 

That is true! Send the young and nimble ones up to top off the reservoir LOL

 

I finally had time to read the entire thread whatstcp posted, and I found many people had issues bleeding the fronts by using the electronic hydraulic pump technique. They say the rears worked well, but the fronts gave them issues. I quoted many of there comments from that thread below.

This leads me to believe either the fronts are slightly bypassed in someway inside the master cylinder in certain conditions, or not much fluid comes out because its just simply designed that way, maybe because the front brakes are so much stronger then the rears it doesn't need much force? Idk

Man there are so many ways to do the same job , that there isnt really a wrong way to do it. But man I have too many choices to pick from lol! I will make a decision and report back if I decide to go through with one. I miss my techstream

Someone did post what TIS says on how to bleed the front brakes.

"3. BLEED BRAKE LINE

(a) Turn the ignition switch to ON, and wait until the pump motor has stopped.
HINT:
Pump operating sound can be heard.

(b) Front brake line.
(1) Connect the vinyl tube to the brake caliper.
(2) Depress the brake pedal several times, then loosen the bleeder plug with the pedal held down (step D).
(3) At the point when the fluid stops coming out, tighten the bleeder plug, then release the brake pedal (step E).
(4) Repeat step D and E until all the air in the fluid has been bled out.
Torque:
11 N·m {110 kgf·cm, 8ft·lbf}
(5) Repeat the above procedures to bleed the other brake line."


https://www.tacomaworld.com/threads...-4x4-trd-off-road-with-speed-bleeders.368080/

 

I have speed bleeders at all 4 corners, so the rears are done with the pump, and the fronts are done the old way. Haven't spent much time worrying why the front brakes aren't powered by the pump.. not a big deal.

 

Hey friends, long time listener, first time caller. While slightly tangential from this thread, resurrecting it with the hope that someone can help me better understand the install procedure for the hydroboost unit (OEM pn: 47050-04092) on the 2nd gen (2014) Tacoma. Mine started leaking inside the cab and needs to be replaced. Seems like a fairly straightforward R&R, but curious if this confangled master cyl/electric pump unit can even be bench bled? I've scoured the web and this forum for install procedure but this is the closest relevant topic I could find. Once installed, based on reading other posts in this thread, the final bleeding procedure seems pretty straightforward as well (elec pump for rear, standard bleeding procedure for front).

Any help would be immensely appreciated. About to go grab my ankles and pick up the part from the dealer...

TIA!