Progress! Drive it!! Sometimes errors and lights clear themselves. Take note of mechanical brake action and pedal feel. Does braking feel right? Is action consistent? How is stopping power?

update 3:

I was driving for 20 miles now with all 3 relays new

I had the results I mentioned in update2 from yesterday
(brake motor is running every second brake action, not triggering the alarm / low accumulator pressure stage#2... I assume the pressure switch has 2 stages, stage #1 is the normal refilling of the accumulator, no alarm, no light here ...stage #2: further pressure drop in the accumulator and pressure below #2 threshold: the alarm sounds/lights go on, this alarm however stops as soon as the accumulator is recharged by the pump/motor).
I think once alarm stage #2 is triggered the code for low accumulator pressure is stored.

So far so good. The only complaints I'd have in this condition would be the 'soft brake pedal' (not enough braking power for my flavor) and the very frequent brake motor after every second brake action. I assume these symptoms are all related to the hydro booster unit and brake calipers, proper bleeding, no electronic glitch here.

However after maybe 1/2 hour drive I had the 'other' alarm started: alarm2 comes with the weird solenoid noise and pump running at all time, alarm2 comes on out of the blue with no brake action involved... it is not triggered by low accumulator pressure and alarm2 is not stopping by itself. I can only stop/reset it by removing the green relay. After reset it will take a little while and it will come on again.

I know now that the replacement of the relays did not solve the issue with alarm2.... meaning the relays are not the root of the alarm2 problem.

As Sam suggested I will exchange the skid control ECU now in the hope that this ECU might stop alarm2
Can I simply swap the ECU or is there more to it?

Best, Martin

Thanks Sam,
in 'update3' I described what happened. Alarm2 come on (alarm2 does the weird sound with constant brake motor running).
At least I know now that the relays are not the source problem for alarm2 .

Also I know now that I have 2 different alarms

Alarm1 = accumulator pressure below stage2 - abnormally low fluid pressure
This alarm comes on when I push the brake hard in sequence for at least 5-10 times. Under normal driving that possibly won't happen easily but I could trigger alarm1 during driving before.
That alarm1 cancels itself after pressure is replenished
(if that happens to other cars... I don't know. I have not experienced it before I had these brake issues last year).
I had this alarm1 after I installed the 'rebuilt' brake motor/pump/accumulator.

Alarm2= has to do with the ABS/TRC/VSC department... it must be an electronic gremlin. If this alarm starts it will not stop any more, unless I pull the green relay. Exchanging the relays did not do anything. This fault is coming back. It appears that Alarm2 is triggered randomly, no braking action involved here.

Martin

I think I mentioned pages ago in this thread that Japanese brake pedal action is softer than German action. It's OK to prefer harder pedal but we do not want to mistake Japanese feel for a problem. If your T4R pedal does not go to floor and there is braking action in the top half of pedal travel, that's normal. What we are looking for is consistent braking action that does not change regardless of temperature or miles.

Pump running every other brake application is a problem and indicates a seal somewhere is not sealing. Caliper internal leak would result in pulling and uneven pad wear. You are not reporting that. That leaves master cylinder / valve block seals. Bad MC seal would lengthen pedal travel and reduce braking power. You are not reporting that (yet). That leaves line bleed and valve block seals. You are probably tired of checking lines for air but do it with engine running. There are valve block seal rebuild kits available.

Thanks Sam,

You are not confirming the pressure switch and my assumption that this is a two stage switch. Is it and has anyone ever seen this brake alarm because of too low stage 2 pressure?
If not normal that the brake motor is running every other brake action.... I am wondering
I am questioning that there is an internal leak (only), unless that inner leak is substantial which might be the case.
There might be something that draws a lot of juice (brake fluid) during braking action too (might be air in the system or some other spring effect).
My brake pedal does engage only properly if I really press it down to almost to the bottom.
I had a much, much better pedal response and brake power after I rebuilt the brakes 4 years ago when I bought the 4R. I had one completely seized caliper piston in front and the others were more of less stuck. I think after rebuilding these calipers It felt as if I had double the braking power. What I wanted to say: I was in the situation before and I am not happy with the braking power, simply because I know it can be much better.
After the rebuilding (2.5-3 years after rebuilding the brakes)I felt that the braking power was declining but these are the moment when I was not 100% sure if I am overly sensitive or if it really went downhill.

I am so sick of these brakes that I bought Dorman sets and will rebuild all calipers. I'll know when I have these calipers on the bench.

I am assuming the soft brake pedal in general has nothing to do with the internal fluid leak inside the hydro booster. I am still assuming the master cylinder is not leaking..... well....at least not much leaking.

The first leakage point in a hdyraulic system with a pump and accumulator is the check valve between the two. To this day I am wondering where the check valve is for the accumulator. In a hydraulic system there must be a check valve for proper pump action and to make sure the stored fluid under pressure is stored tight. That is the check valve. It must be after the pump (I think I saw a 3 cylinder pump in Mercedes Star formation.... anyone opened that pump up and can show the interiors?)
I opened briefly the outer covers (with big Allen key) of my spare pump cylinders but did not get far. Below the 3 covers there are plates with an off center hole that re quires a special tool to remove...so that plate cannot be removed easily. It is not made for repairs I guess.
I might cut open one pump that i still have here for parts and see what is hiding there. This was the original pump.... while I am running the rebuilt pump currently.

At some point when I find myself in despair I might bite the bullet and simply buy a new Toyota hydro booster unit.... just because too many things run parallel in there (master brake cylinder/hydraulic pump/check valve/accumulator/ pressure switch/ABS/TRC/ VCS Solenoids and valves.. leakage)
1) With a new hydro booster unit I can at least be sure that this piece of hardware works per specs (and I am 1.4K 'lighter').
2) With rebuilt calipers/new brake pads that end of the hardware would be checked.
3) After that the only part left -that I am aware of- would be the skid control ECU.
Probably I will change that one first as it should arrive any day and it should be relatively easy to find and exchange. I can then see if a 'new' ECU changes anything.

What do you think of that plan? I know this is a lot of money but on the other hand I don't want to spend the rest of my time and your time with guess work about an overly complicated brake system.
I simply want to drive that car safely.

Martin

Well that stinks, I was hoping your were getting somewhere. I'm kinda thinking you may have two issues. The original one and one brought on by the supposed "reman" assembly.

Two questions, you mentioned squishy pedal, was that there before the alarms started? Second question, did any ABS codes disappear?

This is the root cause IMO. Squishy pedal that engages almost at the bottom is consistent with master cylinder internal leak. Here is the repair kit:

04493-60350 Toyota 4Runner GX470 Cruiser OEM Brake Master Cylinder Repair Kit | eBay

I'm beginning to suspect Martin's original fix muddied the waters. He has put a lot of effort into this so am going to give him plenty of latitude. I think we are in agreement that we want Martin to enjoy TR4 brakes as much as we do.

Hi Mike

thanks, yes that squishy brake pedal was there before the failure of the brake system last fall. I am relatively sensitive regarding brakes and I was planning to renovate the brake calipers before the brake failure event.... So this issue was present before.
I am aware the squishy brake pedal is a hardware or hydraulic issue (master brake cylinder leaking or brake calipers stuck or air in the hydraulic system)

The brake alarm with the ABS/TRC acting up (constant brake motor, weird solenoid noise) is the second item and here I can only think it is the electronics (skid control ECU) or something inside the solenoid/valve block.

ABS codes.... good question.
I was trying to understand the codes, but I am not sure.
initially I had 8 stored codes. I believe I have 2 basic events that are here in the code mix
EVENT 1: Super low accumulator pressure triggering the alarm (cancels itself but might trigger a code)
EVENT 2: Solenoid block activated creating this weird hissing sound and constant brake motor

1) C0278 open/short Circuit in Antilock Brake System Solenoid Relay Circuit (EVENT 2)
2) C0279 Battery Short Circuit in Anitlock Brake System Solenoid Relay Circuit (EVENT 2)
3) C1223 Malfunction in Antilock Brake System Control System (EVENT 2)
4) C1246 Malfunction in Master Cylinder Pressure Sensor (EVENT 1)
5) C1252 Hydro-Booster Pump Motor Malfunction (EVENT 1)
6) C1253 Hydro-Booster Pump Motor Relay Malfunction (EVENT 1 or EVENT 2)
7) C1254 Pressure Switch Circuit (EVENT 1)
8) C1256 Accumulator Low Pressure Malfunction (EVENT 1)


Event 1 is the low pressure below the Stage 2 pressure (super low pressure).... causing a low pressure alarm and with this the low pressure codes (codes 4-8...my assumption).

This is an event that happens if I am braking hard hitting the pedal several times in short time... like during race driving. This dash alarm is canceled after the pump motor is picking up the required pressure.

Then there is EVENT 2 , the ABS/TRC/VSC event.... this alarm starts out of the blue (after 10 -20 miles of driving after the alarm is canceled by pulling the green relay), no braking involved in triggering this alarm. This Alarm does not cancel itself. I need to pull the relay in order to cancel.

I believe this failure is triggering the 2 relay codes.

I could spend more time and figure out more. My problem is my cheap code reader (I can easily read the codes but cancelling is difficult, it does not always work...driving me nuts).

Martin

Hi Sam,

Master Cylinder internal leak: That could be an option.
Does it explain why my pump motor is coming on every second time I hit the brake?
I don't know how the hydraulics of this system works (a section would help a lot). I just know the good old piston master cylinder.
The old vacuum unit is right behind the master cylinder and simply enhances the push rod force initiated by the leg.
Same with an older air brake (in a Mercedes 600 for instance).

So I guess in the T4R the pressurized fluid from the accumulator is pushing the master cylinder rod in a similar way and the hydraulic push piston multiplying the force of the foot can be relatively small in dimension (compared to a vacuum driven piston).
A fluid leak in that push piston however would not go unnoticed unless the leaking fluid is going right back to the reservoir.
that might be the case.

As the master piston in front is not going down once I keep the leg force I am assuming the front master piston is not leaking. But the one behind multiplying the force....could leak? And thus the constant leak of pressurized fluid?

I wish I could give you a definitive answer but I always go back to fixing root cause first and hoping the rest clears up. We (at least I do) strongly suspect m/c so that would be my next move. I'm on shaky ground here and welcome correction but here goes. True, pump builds pressure but if pressure is leaking past the m/c, pedal will be squishy but we already know that. If there is a pressure sensor downstream of the m/c and it detects low pressure going to the caliper, that could trigger an alarm event that braking failure is imminent and it is. Replacing m/c piston could clear up pressure issues not only at the pedal but also for the ECU. ECU sees low pressure and commands pump to build pressure. This could be why it runs so much.

Those first 2 codes need to be chased down and are probably the same issue. I'm wondering if you have a bad wire connection in the relay/fuse box, under side where the wires attach. You touch the relay and things get better for a bit. South Main Auto has a YT channel, he's a super good troubleshooter for this type of issue. Often the odd intermittent issues he finds are because of "green crusties", as he calls them, on the wire side of a connector. He lives in NY so has the same issue we do with corrosion.

Green crusties, lol. Those are the bane of ignition coils.

Getting back on topic, our OP has the bad luck of experiencing electrical and hydraulic issues. I can see why he does not have confidence as the fix has eluded him. Ironically, all this remote troubleshooting has increased my confidence in the system.

Mike and Sam


Green Crusties:

Is this the copper carbonate hydroxide... copper corrosion... meaning green patina on copper connections?
I have not seen the green copper patina anywhere as of now. The relays are clean, they look new to me.
I haven't looked at the sockets in the fuse box with the microscope but to the naked eye the sockets look good. By removing/wiggling the relays pins rub hard on the socket leads. I removed these relays now various times... so they should be clean.
I could use vinegar/salt solution (or Brasso) and clean the sockets out....
Should I remove the fuse box , look more closely and clean the sockets if any doubt?


Increased confidence in the brake system? Explain to me please.

(I never spent so much time and money with any brake before... and still not knowing how to solve the problem)

Martin

Mike,

You seem to think that the first two codes are the root cause for the EVENT 2 - ABS/TRC/VSC alarm?

1) C0278 open/short Circuit in Antilock Brake System Solenoid Relay Circuit (EVENT 2)
2) C0279 Battery Short Circuit in Anitlock Brake System Solenoid Relay Circuit (EVENT 2)

If so, the simple question is: What is triggering these 2 codes:

open/short circuit in in ABS Solenoid Relay Circuit (assuming ABS Sol Relay being the Green Relay).
And ...Battery Short Circuit in ABS Solenoid Relay

What for example would be a short in a Relay circuit.
What is called a "relay circuit" I am assuming if the relay circuit is the circuit that is staring the motor or the solenoids.
The result of the short would be a closed contact of the ABS Sol relay.
But this does not happen during this alarm at all.
As I explained: With the green relay removed I mimicked a short by directly connecting
[1 and 2- work circuit] with a wire (creating an artificial short in the relay circuit).
But nothing happened.... well I did not leave it in place for very long...
Maybe I should try leaving the short in place for some time?

I am assuming the second code: Battery short in ABS Sol Relay is the same thing, Is it the same code or what is different between the two?
Martin

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