ABS issues

[duncan]

Historically marque specialists re-gassed Citroen spheres. Currently eBay lists new Citroen spheres from £30 up, it would most likely need a thread adapter (I’ve no idea which threads are used Honda & Citroen) but worth a deeper dive?

[Papalazarou]

Historically marque specialists re-gassed Citroen spheres. Currently eBay lists new Citroen spheres from £30 up, it would most likely need a thread adapter (I’ve no idea which threads are used Honda & Citroen) but worth a deeper dive?

That’s a good call Duncan. I wonder how viable that is. I guess it’s all down to the spec. I am really enjoying this thread.

Cheers.

[duncan]

Citroens (of old) used LHM hydraulic which always came with a warning not use in other non Citroen applications. Delving into the web to find out why . .
Seals for conventional brake fluid are a natural rubber blend which is not resistant to hydrocarbon fluids, like LHM. However, seals for LHM will be a nitrile rubber blend which resists oil based (hydrocarbon) fluids and will also resist conventional brake fluids.
Thus it would appear that save for the thread and sealing flare detail Citroen spheres could be considered.
Perhaps someone with a spare Honda sphere from a converted system could measure the thread?

[Kaz-kzukNA1]

Slow to join the conversation and you may have already decided on the future direction so going to just touch on the basic.


If nothing done to your existing ABS and just completely failed, I wouldn’t bother repairing it.
ABS light will result in MOT failure.
Can be disabled though.

However, since you mentioned that the pump was replaced (mechanical pump + electrical motor = expensive), then it’s worth at least doing some tests before upgrading.

You also mentioned that ‘it’s all been rebuilt recently’.

Don’t know what kind of overhaul was done but there are several procedures only available in Japanese workshop manual so may have missed something and contributing to your issue.


For the upgrade, you can find example here; http://www.nsxcb.co.uk/blog.php?1811&blogcategoryid=30

For your reference, as of June/23, Honda has stopped taking any new order for the NSX upgraded modulator.
Don’t think it will be discontinued but no future schedule at this stage.

Waited for months and even for years for the delivery of multiple orders because every time when the expected delivery date got closer, Honda/manufacture postponed it due to manufacturing failure.

Finally, got all three delivered last month but that’s it.
No more new order for the upgraded modulator accepted by Honda.

So, if doing the upgrade, the used S2000 AP1 modulator is one of the proven option for now unless you can source the NSX specific modulator from somewhere else.


Will leave the testing procedure for now but could you clarify the following?

Q1. When you triggered the ABS on purposely, did you feel kick-back at the brake pedal and if yes, was it weak or strong kick-back?

You already owned so many NSX that I assumed that you have some idea on what to expect from the kick-back.


This is the famous website that many refers to for flushing the modulator. http://danoland.com/nsxgarage/brakes/abs/abs.htm


Above link can only flush half of the ABS so not complete but good for understanding the procedure and the connector/relay location.


With the above method, you will be able to manually operate the ABS pump.
Also, you will know how to manually activate each solenoid.

These become handy when testing the abs pump and the accumulator.
Also, whether any high pressure fluid left inside the accumulator or not without the use of OEM ABS T-wrench


I’m aware that you got intermittent ABS light so while the accumulator could be not 100% healthy, it still has some life left with enough nitrogen gas left behind the bladder.
Otherwise, you would always trigger the ABS light after started moving the car and the ABS pump operated more than 120sec.


While it can help, please be aware that one can introduce new issue by applying hard braking on slippery surface to ‘exercise’ the ABS.

This is still recommended by many in order to prevent the sticky/leaky solenoid.
I used to recommend the same.

However, I no longer recommend it and instead, asking the owners to manually flush the accumulator and activate the solenoid in specific way at least once a year.


Most likely your 1st accumulator with your previous NSX was fine and just had so much air inside due to overly ‘exercising the ABS’ or the leaky solenoid issue.

Flushing the accumulator properly and air bleeding the modulator/piston chamber would have fixed it since your solenoids and the pump were not replaced.






If you are happy to remove the accumulator, you can check for the pin hole/puncture of it.

With the heathy accumulator, you can only insert centre punch, allen key, etc just for a few cm from the top, like less than 3cm.
Tiny opening so narrow tool required.


With the punctured bladder or loss of nitrogen gas at the accumulator, the tool can go all the way close to the bottom of the sphere/accumulator, i.e. the diameter of the sphere.


Years ago, I read somewhere on Prime about recharging/regas of the accumulator so probably can be done but it’s under extremely high pressure so may struggle with the delivery method.


Ultimately, best upgrading to the latest one body ABS modulator but you can buy some time if your existing ABS has some life left.


Kaz

[Papalazarou]

Thanks Kaz,

I drove the car today to see exactly how it reacted to different braking input.
Driving from cold and applying a small amount of braking force, triggered the chirping and the pedal to feel as if the ABS had been triggered when it had not; so kick-back and the feeling of the pedal falling through its travel.
At low to medium speeds the chirping would kick in regularly when not using the brakes.
At higher speeds with higher braking force, the brakes worked fine, but would chirp and kick when I backed off the brakes but was still applying some pressure.
Overall the kick was quite strong, but most disconcerting was the clunk as the pedal would fall through it’s travel as though I had lost traction.
The picture is the invoice for the seals replaced at the time of the rebuild.
Apparently when everything had been rebuilt/replaced, the previous owner reported that the ABS was improved, but still displayed the above characteristics at times.

[Kaz-kzukNA1]

I now understood why you were using the word ‘chirping’ unlike many owners referring the ABS pump noise as ‘squeaking’, ‘rattling’, etc.

Your issue is not the ABS.
It’s the wheel speed sensor signal quality (noise) issue.

You may still have certain ABS issue but from your test driving report, it’s doing what it should.

It explains the chirping and not squeaking noise plus the reason for the sunk brake pedal.
It will trigger the ABS light from time to time due to ABS pump continuously operating while the solenoid releasing the fluid back to the reservoir before accumulator reaching the targetted pressure.
In my personal view, classic ABS has design flaw.

Experienced exactly the same thing on few NSX with the classic ABS.
I still remember how scary it was drivng such NSX for the first time.

Later, it also happened on my NSX but with the upgraded ABS that I had better picture on what was going on.

This is what I reported at that time;
http://www.nsxcb.co.uk/entry.php?85-...and-14)-Part-3


With the upgraded ABS brain power, it can detect this signal quality issue and will trigger the ABS code #12, 14, 16 or 18.
Thus, you'll get the ABS light.

Unfortunately, with the classic ABS, the brain power is not enough that it can’t detect this failure mode and thus, no error codes assigned.
Thus, no ABS light.

Unless you can monitor the sensor signal while driving, it’s hard to find which sensor has the noise issue.

The simple resistance check will show the normal reading.
Never tried but after driving the car to warm up the sensor and then applying lots and lots of cold spray over the sensor body ‘may’ highlight something.


For your reference, only few examples so not definite but so far, this sensor noise issue happened only at the front sensors.
Again, it can happen at the rear side as well so please take that into your consideration.


From your photo, as expected, part of the o-ring at the piston body and the solenoid were replaced during the overhaul but not all of them.
The ABS pump is indeed the whole lot, both the mechanical pump + the electrical motor so expensive.
Most likely you have some air at the piston chamber side.
The flushing method in the link in my last post won't be able to flush this side of the ABS.


As investment made by the previous owner into your existing ABS, you could try replacing the w/speed sensor (probably try the fronts first) and then evaluate the upgrade option.
You'll need to replace at least one sensor any way.
Or, go for the upgrade and let the system to detect the noisy sensor.


Kaz

[Papalazarou]

Thanks Kaz,
I did the flash error codes this morning and got the following;
36 on the ECL
AND
Four quick flashes and one long flash from the ALB. 14?
I had similar symptoms on my first NSX (96 car), but with the TCS ALB lights on.

[Kaz-kzukNA1]

Addition to the 7.5A CLOCK fuse, did you remove the 20A ALB2,3 one before you drove this morning?
If not, the ABS error code was from the past.

CEL #36 is for the TCFC command line between TCS and ECU on non-DBW model.

It can be triggered if you struggle to start the engine, main relay issue, IGSW issue, misfire, etc.

If you saw ABS + TCS lights with sudden misfire like cut due to w/speed sensor failure, CEL #36 can be triggered with or without the actual CEL on the dash.

No CEL on the dash but the code will be stored if detected only once within the one driving cycle.
For example, if you disconnected the TCS controller.

I always get CEL #36 but without the CEL because I disconnected the TCS controller like 25 years ago.


ABS #41 or officially, it’s referred as #4-1.

Front Right w/speed sensor open/short circuit.

However, it won’t be fixed on its own and since TCS gets the level converted w/speed signal through the ABS controller, it should have triggered the TCS light at the same time unless you already disconnected the TCS controller.

This is the reason why I touched on the ALB2,3 fuse at the beginning and if you didn’t see the TCS light, most likely, the code was from the past.

If you did reset the ABS by pulling the ALB2,3 fuse and subsequently got ABS #41 but without the TCS light, at least, you have something to look at for the cause of chirping issue.


Kaz