Brake Gremlin

[werminghausen]

Hi Sam
Here I found a video showing the problems of a relay... I wonder if this is one issue that happens in my case as well?
He is talking about the relay that might jeopardize the ECU with its high voltage ... is that arcing?


https://www.youtube.com/watch?v=OE9TvfyC5EY

 

[SocalSam]

Corroded contacts can cause poor electrical transmission which can lead to overheated circuits. Most sensors rely on voltage signal so it is critical they get clean power. I'm no EE but I know this is not good.

 

[werminghausen]

Thanks Sam,
The green relay: control circuit pin 4 is fed by the ECU signal port 'SR'. The relay power circuit active then feeds into the ABS VSC TRC Actuator ( Port 'BS' at black box of the hydro booster). I think the solenoids are causing this weird sighing noise that I was describing earlier during the alarm.
The modern ECU seem to be much more sensible, and not accepting a worn out relay, compared to the good old electrical circuits from the 60s-90s.

My older son is a software engineer and does also robotics (software, computers, electronics and mechanical). I'll try and get him involved here. He has an oscilloscope.
He could, in theory, measure the voltages during shifts at the old relay and then test a new one in comparison.... and then we should see a difference if the old one is bad.
Wish me good luck that we can find something meaningful.

Martin

 

[MikeinNH67]

Personally, I would not bother trying to clean any relays. I'd want new and to know they are no longer the issue. I've seen issues with relays not contacting well but these Toyota relays seem to stick closed until you tap on them.

Back the hatch window, best bet is to pull the cover off to see how the cables and track look. Living in the similar area as me, I wouldn't be surprised if they are locked up. You could also power the motor directly to see what happens.

 

[werminghausen]

Personally, I would not bother trying to clean any relays. I'd want new and to know they are no longer the issue. I've seen issues with relays not contacting well but these Toyota relays seem to stick closed until you tap on them.

Back the hatch window, best bet is to pull the cover off to see how the cables and track look. Living in the similar area as me, I wouldn't be surprised if they are locked up. You could also power the motor directly to see what happens.

Thanks Mike,

I agree with the relays.
My son was here over the weekend and we tried to test the relays with the oscilloscope. Testing the same way the guy in the video did. It appears that both (old and new green relay) behave the same, no difference in the opening and closing voltage peaks. We measured about +100V peak voltage when energizing the e-magnet (closing the control circuit with 12V) and about -150V when opening the circuit. As I said both relays operated the same and therefore we did not find anything suspicious.
This leads me to believe that the green relay is okay and may be not the reason why the alarm is triggered. I know the pulling/wiggling the green relay can stop/cancel the alarm temporarily but the alarm will come back on in a matter of maybe 10-15 miles so far.
I am assuming at this point that during the operation there is something triggering the alarm and it must have to do with the ABS/TRC/VSC...
With the alarm there comes the whole package (all 4 dash lights plus the alarm sound, the continuous running of servo pump motor, the weirdo signing sounds (probabaly some of the ABS/TRC/VSC solenoids as this sound come from the aluminum block between master cylinder and the black box with the 3 connectors at the side of the hydro booster unit.

My suspicion is that the alarm is not triggered by the Green relay (as they tested okay... but possibly by one of the other 2 relays.
(I agree if one of the relays stick closed then this is an issue for sure... but then I should be able to trigger the alarm by mimicking pins 1-2 closed - by removing the relay and installing a direct wire connection).
If I remove the Blue relay then there is no booster power at all.... very difficult to brake without this relay.
As the Blue relay (ABS MTR relay) seems to be the relay that also operates the servo motor under normal conditions (with ABS not active) I am assuming that this relay is okay (When I wiggle the Green relay and cancel the alarm until the alarm comes on again I can drive and brake absolutely normal for say 10 -15 miles...until the alarm starts again. That tells me that the Pink Relay is probably the trouble maker... if any of the relays is causing the problems.

I was now replacing the pink relay (called TRC MTR relay #89633-24010- remember this relay is activating the servo pump motor as well. During the alarms the servo motor is running non stop and this then could be caused by either the Blue or the Pink relay stuck closed. As the Blue Relay should be okay I am assuming that the Pink one is the problem).

On the first test drive this morning with a new Pink Relay the alarm did not come on. But it does not mean that it can/will not come on at any time.

I also ordered a new Blue relay.... just to not bother with these relays any further.

If I am lucky that was it (Pink or Blue relay bad)

As Mike said it is probably best to replace all 3 relays (Blue, Pink and Green relay) just to take them out of the complicated equation.

Martin

 

[werminghausen]

[Back the hatch window, best bet is to pull the cover off to see how the cables and track look. Living in the similar area as me, I wouldn't be surprised if they are locked up. You could also power the motor directly to see what happens.]

Hi Mike, I'll do as you recommended. I'll pull the cover and see what I find. I also bought a good used rear hatch ECU if need be. It was $30.

Best, Martin

 

[werminghausen]

update:
With the new pink relay the same thing happens...I am starting with the dash lights and alarm off (remember I can 'reset' the alarm by removing and reinstalling the green relay) and I can drive a couple of miles and then out if the blue the alarm is starting.
That means the Pink relay is not the trouble maker either (not the green relay and not the pink relay as I have installed new ones)....
So the last relay missing is the blue one. Still waiting for the new blue relay to arrive.

If am driving without the green relay the brakes work (which is good!) but I have the 4 dash lights on. That is the only mode at this point to drive and avoid the alarm sound.
That triggers this alarm is still a mystery.

Let's brainstorm. I still have 3 options, I think.
1) I still have the blue relay to replace and see if this does solve the issues...We'll see but I doubt this will help.... to be honest at this point.
2) I can replace the ECU (skid control ECU - I bought a used one for replacement. Well it is used but it could solve the issue in case there is a glitch inside the ECU
3) I can replace the hydro booster or try to clean out the existing unit.

What do you think.

 

[SocalSam]

[Back the hatch window, best bet is to pull the cover off to see how the cables and track look. Living in the similar area as me, I wouldn't be surprised if they are locked up. You could also power the motor directly to see what happens.]

Hi Mike, I'll do as you recommended. I'll pull the cover and see what I find. I also bought a good used rear hatch ECU if need be. It was $30.

Best, Martin

Covering the basics... Disconnect FOB radio receiver located in the driver's side rear pillar, IIRC. We want to see if spurious window and door lock issues disappear. Door lock security will lock doors by themselves if doors are unlocked and doors not opened within about 30 seconds. This guards against inadvertent fob unlock.

 

[SocalSam]

update:
With the new pink relay the same thing happens...I am starting with the dash lights and alarm off (remember I can 'reset' the alarm by removing and reinstalling the green relay) and I can drive a couple of miles and then out if the blue the alarm is starting.
That means the Pink relay is not the trouble maker either (not the green relay and not the pink relay as I have installed new ones)....
So the last relay missing is the blue one. Still waiting for the new blue relay to arrive.

If am driving without the green relay the brakes work (which is good!) but I have the 4 dash lights on. That is the only mode at this point to drive and avoid the alarm sound.
That triggers this alarm is still a mystery.

Let's brainstorm. I still have 3 options, I think.
1) I still have the blue relay to replace and see if this does solve the issues...We'll see but I doubt this will help.... to be honest at this point.
2) I can replace the ECU (skid control ECU - I bought a used one for replacement. Well it is used but it could solve the issue in case there is a glitch inside the ECU
3) I can replace the hydro booster or try to clean out the existing unit.

What do you think.

Swap ECU. You have the part.

 

[werminghausen]

update 2:
I received the new blue relay and installed it.
Interestingly there are some different outcomes, at least in detail.
1)-With all 3 new relays the dash lights are off when I turn the key into ignition (that was the same before)
2)- When I press the brake pedal now several times in sequence (engine not running, pressing pedal hard for say 10 times in sequence) the alarm is starting at some point (alarm sound and the 4 dash lights)
That was probably the same before.
3) -After about 10 seconds however the alarm and dash lights stop.... During the 10 seconds time the booster motor is running but there is no weird sighing noise! That is new

So the weird noise did not show and The alarm is canceled after 10 seconds.... that is interesting.
I think what happens: with pressing the brake pedal in rel. fast sequence the accumulator capacity is at a limit and the pump cannot keep up and maintain pressure.... once the pressure is below a minimum threshold the alarm is starting.

I remember that the alarm starting and then stopping the first time on the highway (which scared me big time) was probably exactly the same.

So my question now is: Does this same scenario happen with another (a good) T4R as well (pressing the brake several times and at some point the alarms is starting)? Or does that simply not happen?
If you could give me your experience with your car... that would help.

I have not experienced this behavior prior to the brake alarm issues but I never tried to press the pedal hard in sequence very often either.

If your answer is no.... this does not happen.... then I would suspect that the 'hardware'- hydro booster unit might be in question.

I also don't understand that a bigger amount of brake fluid is pushed through if I press the pedal several times... the amount should be minimal....
If this is true... then another hardware part- the calipers might be in question? Could there be a caliper issue that requires more brake fluid flow that usual?

Best, Martin

 

[SocalSam]

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?

 

[werminghausen]

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

 

[werminghausen]

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?

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

 

[SocalSam]

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.

 

[werminghausen]

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

 

[MikeinNH67]

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?

 

[SocalSam]

...My brake pedal does engage only properly if I really press it down to almost to the bottom...

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

 

[SocalSam]

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?

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.

 

[werminghausen]

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?

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

 

[werminghausen]

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

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?