Is there a way to trigger ABS actuator to combat spongy breakes? (1 Viewer)

[kenavt]

Thanks @kenavt

I was trying to tie your recent observations back to the images from @cartercd that he shared in post #19 and #35 in this thread. I've used the post #35 image to actuate the ABS pump on my '97 80 during a brake fluid flush with good results. I'm up to changing the approach if there is more/better info available but I'm not sure that your observations indicate a change of approach for the goal of activating ABS while flushing brake fluid. Given the overall focus of the thread I thought I'd ask for a little clarification.

I appreciate the ask - my posts were a bit disorganized and very stream of consciousness.

The only change is that instead of shorting pins 1, 2, 3 on the 6-pin connector to ground (as shown in that picture), you should short pins 1, 3, 4 (as described in the picture's text). Pin 2 doesn't do anything in the actuator; Pin 4 actuates solenoid SPL (which I believe to be the line to the front left). Here's an updated picture to illustrate it:

 

[jpoole]

Thanks for the updated photo and explanation. Seems like a solid update and likely what was intended by @cartercd when he originally shared his helpful posts.

 

[Irish Reiver]

Just wanted to circle back to this diagram again. Pin 4 (with the lighter shade of green doesn't have a pin in it. I checked 2 LC's - both 96 and neither has a pin in position 4. Also there isn't a wire feeding that position either. I decided to revert to grounding pins 1,2 & 3 as per the original diagram. The wire colours listed in the diagram also relate to pins 1,2&3. At the moment I don't have confirmed results either way....

 

[Haggis]

Yeah I'm starting to lean towards just deleting ABS. This truck is going to be trail only in a few months and I'm OK living with no ABS on road as I've driven non-ABS cars before. I think that honestly these trucks may stop safer with no ABS than with the poorly functioning one they have.

The ABS on my 2000 Tacoma started to become a PITA. I just unplugged the unit under the hood. My ABS light is now on but I could care less. Been driving it this way for years, brakes fine.

 

[obe12]

I appreciate the ask - my posts were a bit disorganized and very stream of consciousness.

The only change is that instead of shorting pins 1, 2, 3 on the 6-pin connector to ground (as shown in that picture), you should short pins 1, 3, 4 (as described in the picture's text). Pin 2 doesn't do anything in the actuator; Pin 4 actuates solenoid SPL (which I believe to be the line to the front left). Here's an updated picture to illustrate it:

View attachment 3477901

Well I was so hoping I could eliminate the spongy feeling. I followed the 94 diagram, and made the motor run and dump valve one at a time open close, Trying to rid possible air out of the system.

Now I have a pressure bleeder 15 psi regulated bleeding and cycling the ABS Motor/ Dump per circuit, Front L , Front R, and Rear.

Zero improvement so far.

I jacked the truck, installed jack stands, and wheels at 50 mph apply brakes, and allow the ABS to work.
No improvements ….

Haven’t re bleed after that so far.

Sure feels like an “internal leak” in the ABS unit as the pedal builds pressure, the brake pedal sinks under your foot to a point then firms up as the pedal is continually pressed.

If you pump the pedal, it starts the sink pedal feel sooner, and still sinks under your foot to a firmness.

Assuming “dump valve leaking” to when it feels the chamber in one circuit.

Can these units be serviced? Opened up and replace seals and such?

I really do not want to consider doing an ABS delete
Until I try all options first.

Tex

Open to ideas!

 

[ZetheGSD]

Well I was so hoping I could eliminate the spongy feeling. I followed the 94 diagram, and made the motor run and dump valve one at a time open close, Trying to rid possible air out of the system.

Now I have a pressure bleeder 15 psi regulated bleeding and cycling the ABS Motor/ Dump per circuit, Front L , Front R, and Rear.

Zero improvement so far.

I jacked the truck, installed jack stands, and wheels at 50 mph apply brakes, and allow the ABS to work.
No improvements ….

Haven’t re bleed after that so far.

Sure feels like an “internal leak” in the ABS unit as the pedal builds pressure, the brake pedal sinks under your foot to a point then firms up as the pedal is continually pressed.

If you pump the pedal, it starts the sink pedal feel sooner, and still sinks under your foot to a firmness.

Assuming “dump valve leaking” to when it feels the chamber in one circuit.

Can these units be serviced? Opened up and replace seals and such?

I really do not want to consider doing an ABS delete
Until I try all options first.

Tex

Open to ideas!

The last I checked these ABS modules were still available new? With a quick search it looks as though they have become unavailable from Toyota...
I am sure there are rebuilders out there as the 4runner/GX/100 series guys use this type of service all of the time. Good Luck with you journey to keep the ABS. I deleted mine and have never been more happy!

When I was bleeding my lines after replacing everything in my brake system I was able to get some dark rusty fluid from the ABS pump once commanded manually. Pedal never improved.

 

[obe12]

The last I checked these ABS modules were still available new? With a quick search it looks as though they have become unavailable from Toyota...
I am sure there are rebuilders out there as the 4runner/GX/100 series guys use this type of service all of the time. Good Luck with you journey to keep the ABS. I deleted mine and have never been more happy!

When I was bleeding my lines after replacing everything in my brake system I was able to get some dark rusty fluid from the ABS pump once commanded manually. Pedal never improved.

My LC, it did not have any rust in the brake fluid or rust on the frame thank goodness.

ABS works as it advertised on payment , dirt road once you get enough brake pressure to create a slide. The rear lets go 1st on both occasions I tried brake to aviation. Dirt I can get the front to slide too to activate the ABS.

So it appears to work. Now the spongy pedal on initial travel, why is the actual question.

The lSPV must be allowing enough fluid pressure, the rear does lock up. Any more pressure it would be worse and lock up easier.


I get the fact it easier to ditch the system and go old school.

I may try plugging different ports and caping lines to determine where this spongy feeling is happening. Isolate front system, rear system, or LSPV itself.

Tex

 

[rhc404]

When I was bleeding my lines after replacing everything in my brake system I was able to get some dark rusty fluid from the ABS pump once commanded manually. Pedal never improved.

When I pulled the ABS module one of the ports was dry. My theory is if the ABS goes long enough without being activated (whether by service tool or on the road) that seals within the unit corrode and no longer provide a proper seal, and once that happens it may be possible to get the fluid clear, but impossible to pump the air out without rebuilding the module.

 

[obe12]

Today, on jacks stands run wheels up to 50 mph did the braking to cycle ABS and had my friend hold the pedal after a few cycles. I crack actual brake lines out the ABS, and the lines at the LSPV. If air came out I didn’t see it.

The brake pedal was still sinking under my foot, however, a change is noticed.
This sponge area holds the truck now and don’t have to keep pressing pedal to firmness to hold the truck in gear.

Driving, feels pretty good normal driving. The sponge isn’t nearly as noticeable. I did a max braking up to prior to ABS engaging to a stop, at 70 MPH to a complete stop like I did prior to changing anything on the brakes, before at max pedal no ABS, I liked to have overrun my stop area. This concerned me greatly and that night, I ordered hi performance brakes, rotors, pads, calipers and stainless brake line hoses.

Today same speed, same brake point, stopped like 3 truck lengths sooner, with no abs engagement. Max braking before ABS engagement was my goal.
Truck slowed down nice and nothing odd happened.



Abs works, I did that the day before, Jab the brakes and caused ABS to engauge both front and rear. Performed a really true panic stop. Rear broke loose and ABS came in.


So, there was improvement today, Two pumps, brake pedal is hi, let off and wait then one pedal pump, and is a little lower, maybe 1 inch lower. I wished that wasn’t there, but overall there is improvement.

I saw Toyotapartsdeal had a listing for an ABS unit right under 800.00 , but isn’t available. Japan and UAE have no stock, and higher priced.

I still may order unions and fittings to block the return line to the front, see if I can isolate what system circuit the sponge is on. Air, or leaking dump valve or other.

Tex

 

[obe12]

Today, on jacks stands run wheels up to 50 mph did the braking to cycle ABS and had my friend hold the pedal after a few cycles. I crack actual brake lines out the ABS, and the lines at the LSPV. If air came out I didn’t see it.

The brake pedal was still sinking under my foot, however, a change is noticed.
This sponge area holds the truck now and don’t have to keep pressing pedal to firmness to hold the truck in gear.

Driving, feels pretty good normal driving. The sponge isn’t nearly as noticeable. I did a max braking up to prior to ABS engaging to a stop, at 70 MPH to a complete stop like I did prior to changing anything on the brakes, before at max pedal no ABS, I liked to have overrun my stop area. This concerned me greatly and that night, I ordered hi performance brakes, rotors, pads, calipers and stainless brake line hoses.

Today same speed, same brake point, stopped like 3 truck lengths sooner, with no abs engagement. Max braking before ABS engagement was my goal.
Truck slowed down nice and nothing odd happened.



Abs works, I did that the day before, Jab the brakes and caused ABS to engauge both front and rear. Performed a really true panic stop. Rear broke loose and ABS came in.


So, there was improvement today, Two pumps, brake pedal is hi, let off and wait then one pedal pump, and is a little lower, maybe 1 inch lower. I wished that wasn’t there, but overall there is improvement.

I saw Toyotapartsdeal had a listing for an ABS unit right under 800.00 , but isn’t available. Japan and UAE have no stock, and higher priced.

I still may order unions and fittings to block the return line to the front, see if I can isolate what system circuit the sponge is on. Air, or leaking dump valve or other.

Tex

Well today, let’s report this as fixed complete. If it stays fixed is yet to be determined.

I don’t believe much in it fixes itself, air in brakes can be tricky… rapid brake reps I have seen had to get air out. Like foams the fluid and air hasn’t formed a bubble yet kinda of thing.

Time sometimes helps, in case Motorcycle TIE the brake lever or pedal on and let it side over night, it amazing results the next day. Why it helps, pushes the air out once a bubble forms. I seen it many times work just like that, overnight good to go.

Well my truck, yesterday a little spongy feel left, normally I check for air, pump twice record brake position, take foot off let it sit. One press and record position. If same then adjustment good on drum, and no air.

That check revealed yesterday, pedal on wait a press , lower pedal about a thickness of a sole of a shoe lower pedal and a little spongy feel and stops the truck fine.

Today, two pedal pump and brake pedal height of Has Pedal height, stops the truck in gear moving slowing.

Take foot off wait, one brake pedal apply and same position now. If not maybe 1/4 of an inch lower to stop the truck maybe. No spong!
If an air bubble was there yesterday and or foamed fluid, the bubble formed and burped it way out the mater cylinder is the only place it could have gone. But it’s gone. Sitting overnight helped it in this case.
Normal brake pedal feel now… omg I am happy about that.

ABS is a great thing when it works, and town driving you need it here in Dallas Ft Worth. Just last night in my 100 I had a max brake effort to avoid an idiot jumping into my lane and slamming on the brakes to avoid traffic stopping. I easily slowed but it’s the person behind me and behind them that worries me. If they are paying attention or not.

That lack of attention is where ABS will
And can help. Under panic mode you do not have fine motor skills to regulate foot pressure very well. Then Slide to impact normally happens. Last night that happened almost when I saw the car behind me nose dive and I stepped out on the shoulder and they parked in my spot. My wife freaked out a
Until she saw the car come up beside us.

Anyway I wanted to keep the ABS working if I could and it is currently. Hope it stays that way.

The fix , magor determination, jack the truck up, all
4 wheels , spin wheels up, apply brakes enough to engauge the ABS. Hold pedal and bleed.
I started ABS out lines and worked my way back to the actual lines on the LSPV. Took some doing… but it worked.

I have a pressure bleeder and master cylinder adapter and pressure bleed the brakes. That didn’t help at all. Cycling the ABS did.
I tried pressure bleeding and hot wire ABS motor and dump valves, that didn’t help.
Actually foot brake pressure and cycling the ABS had results. I actually drove it and engaged ABS 6 times on gravel. Resulted in no improvements.
Only bleeding immediately after cycling the ABS resulted positive results in my case.

I check for TSBs on this issue and found non.
This is a temperamental system the worse I have ever ran across in working on cars / trucks since 1983 professionally. 1 gen 1800 Goldwing ranks number 2 as difficult bleed. Speed bleeders on that makes it easy now, and know the sequence.

Good luck to any others with this issue.

Tex