4Runner/GX electric brake booster w/ ABS

[rockota]

Victim - 04 Tacoma. Front brakes have always been an issue. Was factory single diaphragm booster/stock MC w/ Wilwood calipers/rotors for a long time. Sucked.

Due to the position of the 4wu shock towers w/ the 14" shocks, I cannot fit a dual diaphragm booster. So I've played with ~10 different MC's and have switched to RAM calipers on JK rotors. Still sucks.

So i'm playing around with an electric MC/Booster out of a 2002 4Runner. I believe it's the same that is used in GX's and 4th gen 4Runners. The ABS module is built-on to the MC itself. I don't have room for the ABS module.

So i'm contemplating making a block-off plate. Unless, that is, i can find an electric booster/non-ABS MC... which I've thus far had no luck finding. If I can get rid of the ABS module, I'll have plenty of room.

thinking a 1" thick aluminum block machined flat should work. Or perhaps even trashing the ABS computer and "welding up" the ports in the existing aluminum adapter.

Ideas? Thoughts? I *really* don't want to have to cut off the shock mounts....

 

[Rbx]

Interesting, I have the 4WU setup also but on a 88 4runner. I was able to install hydroboost but making my own Mount, but the angle of the plunger is janky at best. I’ve been looking at the yota hydro, but I’m not sure if I could wire it up properly as I’ve read it’s a very integrated unit.
good luck.

 

[rockota]

Interesting, I have the 4WU setup also but on a 88 4runner. I was able to install hydroboost but making my own Mount, but the angle of the plunger is janky at best. I’ve been looking at the yota hydro, but I’m not sure if I could wire it up properly as I’ve read it’s a very integrated unit.
good luck.

from what I can tell... this *could* run on two wires if the ABS module was removed. Maybe.

 

[Provience]

i'm curious if the electric module would even work with the ABS removed edit: <-that is a stupid statement. of course it will work without the ABS computer, that is what it does when there is a system failure how well? I dunno...but if you've already got it, give it a shot on the bench and see how it feels.

do you have a picture of your firewall? hydroboost seems like the easiest option, otherwise, I did scrap out a dual ~10" booster and short master cylinder off a 1998 Dodge 2500 5.9 (gas) van which was a pretty compact setup.

 

[rockota]

i'm curious if the electric module would even work with the ABS removed edit: <-that is a stupid statement. of course it will work without the ABS computer, that is what it does when there is a system failure how well? I dunno...but if you've already got it, give it a shot on the bench and see how it feels.

do you have a picture of your firewall? hydroboost seems like the easiest option, otherwise, I did scrap out a dual ~10" booster and short master cylinder off a 1998 Dodge 2500 5.9 (gas) van which was a pretty compact setup.

can't fit a dual of any size... Hydroboost might work, but I admit i know nothing about the snowball effect of that. Currently has a Howe pump and hydro assist...

This should give you an idea how tight it is. IIRC, the MC is a Ford E350 van series. 1.125" bore with ports on the inside (again, clearance)

 

[Provience]

hydroboost just plugs in between the pump and the steering box, pretty easy. with as close as that is, you'd need to go to a junkyard and measure the size though and see if it will fit. they are not as big around, but they are square and longer so even that might not fit.

unless you like spending money, vanco and other aftermarket "hot rod" hydroboost kits are offered in more compact setups, heck there are even remote hyrdroboost hotrod units that would work well.

 

[mudtoy67]

This is an interesting idea, I'd like to see if you can figure this out as it might be a good alternative for power brakes when you can't use engine vacuum (boost).

I don't think you can just do a block off plate. You're going to have to figure out which port goes to which wheel and include that port in your block to be able to complete each brake circuit.

I found a couple diagrams that seem to be close to what I think is going on in the toyota master/abs setup.

It's kind of a weird setup because it looks like the rear brakes don't receive any pedal input, only pressure from the hyd pump (HCU). This makes a bit of sense to me though because, when I did the brakes on my 2008 4runner, cracking the bleeder on either rear brake would cause the HCU to start pumping and the fluid would continue to flow from the bleeder without pedal input.

At minimum, it looks like you'll need 3 circuits in the block (left frt, right frt, and rear). Each will have 2 ports, one inlet coming from the MC to the block then connecting (within the block) to an outlet going from the block back to the MC (which then connect to the brake line ports on the front of the MC).

The ABS outlet valve return to reservoir (top left line of the valve block above) most likely can be left blocked.

So, this accounts for 7 ports. Looking at a pic of the abs module gasket (below) there are 9 ports crossing between the module and the MC. You'll have to do some testing to see figure out the missing 2. In the diagram above there is a "main valve" which appears to be an electric solenoid. Check and see if this is built into the abs module. It looks like this will need to be retained as it facilitates fluid inlet and return to reservoir from the front wheels depending on valve open/closed.



Where things get extra murky is how the HCU is controlled. There's two possibilities here, one being the HCU runs at full pressure and the spool valve (control valve above) attached to the pedal throttles the fluid pressure to the wheels based on pedal input. The other could be that the HCU is modulated and varies pressure depending on primary ECU control. If it's the first then the HCU could maybe be controlled by a simple relay turned on/off by the pressure switch on the bottom side of the MC. If modulated then you're having to maintain some form of computer control. Also, that "main valve" has to be cut on/off somehow. Is there any specific computer input or is it as simple as connecting to the brake light switch?

 

[rockota]

This is an interesting idea, I'd like to see if you can figure this out as it might be a good alternative for power brakes when you can't use engine vacuum (boost).

I don't think you can just do a block off plate. You're going to have to figure out which port goes to which wheel and include that port in your block to be able to complete each brake circuit.

I found a couple diagrams that seem to be close to what I think is going on in the toyota master/abs setup.



It's kind of a weird setup because it looks like the rear brakes don't receive any pedal input, only pressure from the hyd pump (HCU). This makes a bit of sense to me though because, when I did the brakes on my 2008 4runner, cracking the bleeder on either rear brake would cause the HCU to start pumping and the fluid would continue to flow from the bleeder without pedal input.

At minimum, it looks like you'll need 3 circuits in the block (left frt, right frt, and rear). Each will have 2 ports, one inlet coming from the MC to the block then connecting (within the block) to an outlet going from the block back to the MC (which then connect to the brake line ports on the front of the MC).

The ABS outlet valve return to reservoir (top left line of the valve block above) most likely can be left blocked.

So, this accounts for 7 ports. Looking at a pic of the abs module gasket (below) there are 9 ports crossing between the module and the MC. You'll have to do some testing to see figure out the missing 2. In the diagram above there is a "main valve" which appears to be an electric solenoid. Check and see if this is built into the abs module. It looks like this will need to be retained as it facilitates fluid inlet and return to reservoir from the front wheels depending on valve open/closed.

<snip>

Where things get extra murky is how the HCU is controlled. There's two possibilities here, one being the HCU runs at full pressure and the spool valve (control valve above) attached to the pedal throttles the fluid pressure to the wheels based on pedal input. The other could be that the HCU is modulated and varies pressure depending on primary ECU control. If it's the first then the HCU could maybe be controlled by a simple relay turned on/off by the pressure switch on the bottom side of the MC. If modulated then you're having to maintain some form of computer control. Also, that "main valve" has to be cut on/off somehow. Is there any specific computer input or is it as simple as connecting to the brake light switch?

There are 4 lines coming off the MC - but none of them are from the ABS module. So I am *assuming* that the ABS module just adjusts the pressure to each tire based on speed sensors, VSV, etc... So my hope is that I can get direct pressure out of the MC w/o the ABS module at all. But reading your explanation in red, makes me think that my idea will not work w/o a ported plate.

So that makes me wonder if I can remove the plastic ABS computer and simply plug the ports on that side. It'd gain me about 1.25" of space.

Fortunately, i have an 02 4Runner sitting here as well, so I have a reference for the lines.

It's going to suck if I destroy an expensive MC... But not as much as if I have to cut shock mounts off the frame, move down to 12" shocks, etc... just to get room to fix the brakes. Or... buy a Diamond axle with Toyota brakes and going back to the stock booster/MC. Nothing's inexpensive.

EDIT: It appears that this might be the same MC as on the Hummer H3 and Mitsubishi Montero of certain years.

 

[Rbx]

Hydroboost and Hyydromax brakes, the boosters are slightly different depending on the name. The Hydromax, seems to be smaller than the common hydroboost GM uses.
I know you are going with the E-boost, just wanted to post another option... hydromax link below.

 

[rockota]

this is also kind of interesting... and fully optioned, minus MC, is about the same price as a hydroboost...

https://www.powerbrakeservice.net/noname.html

 

[rockota]

Hydroboost and Hyydromax brakes, the boosters are slightly different depending on the name. The Hydromax, seems to be smaller than the common hydroboost GM uses.
I know you are going with the E-boost, just wanted to post another option... hydromax link below.

was looking at those as well...

Seems like there might be other options for e-boos as well. Escalade ESV, possibly.

I'm going to check out a lot of options - could be interesting education if nothing else.

 

[Rbx]

Oh, didn’t realize some GMs have e-boosters. I have a bit more room than you do, but not much. One thing I’ve read is that if the booster plunger rod is at an angle when it connects to the pedal linkage, the seals wear quicker and pedal feel (obviously) may be squishy. The nice thing about hydroboost is that it comes with a plate/adapter depending on the vehicle it came out of. Most full size vehicles had it come straight out of the fire wall, but the Astro van booster adapter pitches the whole booster downwards. So, maybe you can use the adapter to direct the booster a bit to eek out more room for install and service.

 

[Rbx]

Few shots of my junk, had to limp it down to my shop to yank the tired 3slo, which is why shit is a total mess.

 

[mudtoy67]

Found this thread on ih8mud. Tons of master/booster info.

https://forum.ih8mud.com/threads/mas...ld-diy.406533/

Also mentioned in that thread is a link to what sounds like Toyota's version of alldata. Might could find a brake hydraulics diagram plus I'm sure there's function/diagnostics that could help you figure out how a way to bypass the abs. It's a subscription like alldata, but for 20 bucks/2 days you could probably find everything you need.

https://techinfo.toyota.com

If you had room to keep the abs module, I wonder if you could control the abs solenoids individually with switches on the dash. Electronic cutting brakes!

 

[rockota]

what's the length of that unit?

Actually - if you don't mind...

What's the length and width of the hydro-boos? What's the distance from the firewall to the shock tower?

And I don't recall... did your generation truck have the aluminum spacer between the firewall and booster?

 

[rockota]

Found this thread on ih8mud. Tons of master/booster info.

https://forum.ih8mud.com/threads/mas...ld-diy.406533/

Also mentioned in that thread is a link to what sounds like Toyota's version of alldata. Might could find a brake hydraulics diagram plus I'm sure there's function/diagnostics that could help you figure out how a way to bypass the abs. It's a subscription like alldata, but for 20 bucks/2 days you could probably find everything you need.

https://techinfo.toyota.com

If you had room to keep the abs module, I wonder if you could control the abs solenoids individually with switches on the dash. Electronic cutting brakes!

dang... that thread makes me want to go hydroboost.

The idea about using the ABS solenoids is interesting... basically a poor man's version of Toyota's crawl control or traction control.

It's not a bad idea. But I just want to get this thing driving. Wife wants to drive it to Church. :D

 

[aczlan]

Here are some pictures/dimensions of a Hydroboost unit in a 2005 Yukon 1500 if that helps.

Aaron Z

 

[aczlan]

And the last few that I couldn't put on the first post:


Aaron Z

 

[rockota]

That's very helpful! Thanks!

 

[aczlan]

That's very helpful! Thanks!

Let me know if you need other dimensions.

Aaron Z

 

[Yotota]

dang... that thread makes me want to go hydroboost.

The idea about using the ABS solenoids is interesting... basically a poor man's version of Toyota's crawl control or traction control.

It's not a bad idea. But I just want to get this thing driving. Wife wants to drive it to Church. :D

An idea just popped in my head from this...

I wonder if it would be possible to manually control the ABS pump with switches, and use it to brake individual wheels as cutting brakes.

Anyone know if this is possible?

 

[rockota]

An idea just popped in my head from this...

I wonder if it would be possible to manually control the ABS pump with switches, and use it to brake individual wheels as cutting brakes.

Anyone know if this is possible?

I've been staring at the... flow(?).... diagram trying to see if it's even possible for this to work w/o the ABS computer.... I'm not sure now. I suspect you could do something similar to your idea, but i'm honestly confused how the flow works...

 

[mudtoy67]

An idea just popped in my head from this...

I wonder if it would be possible to manually control the ABS pump with switches, and use it to brake individual wheels as cutting brakes.

Anyone know if this is possible?

Brilliant idea.

 

[mudtoy67]

I've been staring at the... flow(?).... diagram trying to see if it's even possible for this to work w/o the ABS computer.... I'm not sure now. I suspect you could do something similar to your idea, but i'm honestly confused how the flow works...

In reading the basics about how abs works, when a wheel loses traction, the "pressure holding" solenoid closes. This gives the wheel a chance to move regardless if the brake is pressed harder. If the wheel still doesn't move the "pressure releasing" solenoid opens to bleed some pressure off. This cycle repeats until the wheel starts moving again, vehicle stops, or brakes are released.

I think to use it as a cutting brake would just be a matter of depressing the brake and energizing the pressure holding valve of the wheel you want to hold. Then let go of the brake. De-energize the solenoid when you're done cutting. This is assuming the solenoids can stay closed with pressure from the opposite side than normal.

 

[Yotota]

In reading the basics about how abs works, when a wheel loses traction, the "pressure holding" solenoid closes. This gives the wheel a chance to move regardless if the brake is pressed harder. If the wheel still doesn't move the "pressure releasing" solenoid opens to bleed some pressure off. This cycle repeats until the wheel starts moving again, vehicle stops, or brakes are released.

I think to use it as a cutting brake would just be a matter of depressing the brake and energizing the pressure holding valve of the wheel you want to hold. Then let go of the brake. De-energize the solenoid when you're done cutting. This is assuming the solenoids can stay closed with pressure from the opposite side than normal.

It depends on the vehicle, but a Toyota with Atrac/VSC has the ability to actuate the brakes with the ABS pump too.

​​​​​A simple older style ABS pump like on a 3rd Gen 4runner should only be able to lock the solenoids and possibly retain pressure in the line. Or maybe not, if it allows the pressure to bleed off once it closes.

 

[Yotota]

I've been staring at the... flow(?).... diagram trying to see if it's even possible for this to work w/o the ABS computer.... I'm not sure now. I suspect you could do something similar to your idea, but i'm honestly confused how the flow works...

It's a somewhat normal-ish hydraulic diagram... :D
But it appears that the pressure side of the ABS pump is able to go through the STR valve and then actuate the individual calipers through the Switching and Control Solenoid Valves. Then it's a matter of whether or not the Pressure Holding valves (which might just mechanical check valves) allow pressure to be held at a wheel when the Solenoid Valves are shut, but the master cylinder is not providing pressure.

 

[Provience]

It's a somewhat normal-ish hydraulic diagram... :D
But it appears that the pressure side of the ABS pump is able to go through the STR valve and then actuate the individual calipers through the Switching and Control Solenoid Valves. Then it's a matter of whether or not the Pressure Holding valves (which might just mechanical check valves) allow pressure to be held at a wheel when the Solenoid Valves are shut, but the master cylinder is not providing pressure.

honestly it looks like the master cylinder is just a suggestion and a signal i was looking at the brakes on my wifes escape hybrid, which alternates between engine braking and service brakes as needed. It's got this super small single pot "master" cylinder on the firewall that sends a hydraulic signal to the rather large ABS control module. the ABS has a motor and accumulator similar to the toyota diagram above and then the module varies the brakes based on how much signal pressure from the "master" cylinder versus how much speed drop the electric engine is able to generate versus wheel speed slip.

"quotes" because it doesn't directly control shit

i would absolutely believe that the pressure holding and reducing valves are "normal" electric check valves. if you are doing lots of offroading the normal ABS systems can have trouble keeping up compared to a static locker, but to use one as a cutting brake where you don't need it to be instant would be simple. you would need to be able to kick on the pump motor, actuate the solenoids to send brakes to the right tire, and then keep the holding/reducing valves appropriately locked.

 

[rockota]

It's a somewhat normal-ish hydraulic diagram... :D
But it appears that the pressure side of the ABS pump is able to go through the STR valve and then actuate the individual calipers through the Switching and Control Solenoid Valves. Then it's a matter of whether or not the Pressure Holding valves (which might just mechanical check valves) allow pressure to be held at a wheel when the Solenoid Valves are shut, but the master cylinder is not providing pressure.

Yeah... uh... that’s what I meant.

dude - I sell software... hydraulic systems aren’t my forte!

so the other question that lingers... can this work w/o am energized abs control module?

if Toyota (or anyone else) made one of these in a non-abs format, I think it could be a killer option for space constrained setups like mine...

I was actually looking at Tesla electric masters yesterday...

 

[rockota]

It depends on the vehicle, but a Toyota with Atrac/VSC has the ability to actuate the brakes with the ABS pump too.

​​​​​A simple older style ABS pump like on a 3rd Gen 4runner should only be able to lock the solenoids and possibly retain pressure in the line. Or maybe not, if it allows the pressure to bleed off once it closes.

Pretty sure the 3rd gen 4runner can actuate the brakes when VSC is turned on. I did the vsc mod within the first week of owning my 02... because it would kick in going around a curve on the county road near my house. Scary crap.... now it’s on a switch.

 

[Yotota]

honestly it looks like the master cylinder is just a suggestion and a signal i was looking at the brakes on my wifes escape hybrid, which alternates between engine braking and service brakes as needed. It's got this super small single pot "master" cylinder on the firewall that sends a hydraulic signal to the rather large ABS control module. the ABS has a motor and accumulator similar to the toyota diagram above and then the module varies the brakes based on how much signal pressure from the "master" cylinder versus how much speed drop the electric engine is able to generate versus wheel speed slip.

"quotes" because it doesn't directly control shit

i would absolutely believe that the pressure holding and reducing valves are "normal" electric check valves. if you are doing lots of offroading the normal ABS systems can have trouble keeping up compared to a static locker, but to use one as a cutting brake where you don't need it to be instant would be simple. you would need to be able to kick on the pump motor, actuate the solenoids to send brakes to the right tire, and then keep the holding/reducing valves appropriately locked.

So I just ran through the EWD for an 03 4runner with VSC/ATRAC, and the pinout for the ABS actuator might actually be simple enough to work *with the right controls*. You're right - there are individual inputs for all 12 valves - STR, SA1-3, PH1-4, and PR1-4. The pump motor has individual inputs, and the high/low pressure valves send a signal back to the VSC computer to turn the pump on/off. If this was all rated for binary 12V signals it could probably run off a set of relays and switches. If the signals were reduced voltage or variable it would be a different can of worms.