Brake Fluid Leak at Bottom of ABS

[Heineken]

When checking my garage today I noticed suspicious marks on the concrete floor.
As the front right of the NSX is free of the typical fluids found in front engine cars (like oil, power steering fluid and the like) the first thing I checked was the ABS brake fluid level.
It was near the 'low' mark even though I remembered it to be at 'full' mark about a year ago ..

The brake fluid at the master cylinder was perfectly fine, though.

Looking under the car, the drops on the floor were exactly below the lower mounting bracket of the ABS unit and the bracket was wet:

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Before trying to disassemble everything I wanted to ask if it might be a familiar issue as it strikes me a little odd as of where the bracket is wet (all up to the mounting bolts) and that it seem to have no effect whatsoever on the master cylinder fluid level.

PS: The ABS was not exercised recently but could it be an overflow-during-pump-run issue?

[goldnsx]

overflow-during-pump-run issue?
More sort of a "overflow while not using the car or a stuck solenoid or debris around the gasket. Quite common on older cars but certainly not funny.

[Heineken]

So you're suspecting a not-sufficiently-closing valve probably in team with foamed up brake fluid in the pressure chamber?
I'm currently pondering what to do about it. The reservoir was topped-up of course and I'll probably clean the area with brake cleaner. Additionally I could replace the brake fluid and exercise the pump and valves manually and hope that it clears things up .. I'm not expecting too much from that ABS anyway as long as it stops leaking on parts and the floor :-)

[goldnsx]

Yes, that's the way to go. Exercising all solenoids and hoping that you get as much junk out of the system as possible. There's somehow a description somewhere but I can't help you as I went with the newer pump anyway.

Some people have taken the unit completely apart. Some went with the later pump, much better anyway.

[Heineken]

Well, looks like another busy weekend :)

PS: Finding the descriptions should be no problem, I remember at least one PDF for a rebuild and several videos on how to flush it manually.

[britlude]

the ABS system is completely separate from the rest of the braking system, save for 4 pistons controlled by the solenoids.... that's why the ABS system fluid can be completely drained without affecting the main brake fluid reservoir.....

[goldnsx]

BTW what happened to the German forum?

[goldnsx]

the ABS system si completely separate from the rest of the brakingg system, save for 4 pistons controlled by the solenoids.... that's why the ABS system fluid can be completely drained without affecting the main brake fluid reservoir.....
That's interesting as I've my newer pump since 10 years now and completely forgot how the old pump works. Problem is that I know of an NSX where the brake pedal is ultra long (not safe!) and the ALB reservoir is empty. I correlated the long pedal to this but now I'm not sure where to start. It's not my car...just trying to help out.

[Heineken]

BTW what happened to the German forum?

The one I joined was never much of a help to me, to be honest. The things I posted (like how to repair broken plastics, capacitor replacement, Tokyo Motor Show) weren't taken up in any useful way (except from a friend). It's basically a three-to-four man show and some of them are seriously difficult to discuss with ..

[Heineken]

If I understood the technical description correctly than the wheel pressure control is realized by two separate fluid systems:

The ABS system
The master cylinder and caliper system

Both systems are interconnected via a sliding piston, effectively separating both fluids but allows the ABS system to manipulate the master cylinder / caliper pressure

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If high pressure from the accumulator is pushed into chamber C (by opening the inlet valve an closing the outlet valve) the sliding piston is pushed upwards and:

disconnects the master cylinder from the caliper
enlarges chamber B which causes the caliper pressure to drop
reduces chamber A which pushes back the pedal

The volume pushed back into the master cylinder (via chamber A) matches the volume by which the chamber B was enlarged. As a result, the brake pedal is pushed back to a position that matches the lower pressure of the caliper.

When the wheel stops locking the inlet valve is closed and the outlet valve opened. Chamber C is then connected to the pressureless reservoir and quickly discharges that way, supported by the master cylinder pressure in chamber A. Once the sliding valve hits bottom, the master cylinder and the caliper are once again connected. Pressure at the caliper can then be increased the usual way (by further depressing the brake pedal).

Let's hope that description makes sense and not only to me :D

[goldnsx]

The one I joined was never much of a help to me, to be honest. The things I posted (like how to repair broken plastics, capacitor replacement, Tokyo Motor Show) weren't taken up in any useful way (except from a friend). It's basically a three-to-four man show and some of them are seriously difficult to discuss with ..
Same experiences for me with that forum. Plus two "wannabe part dealers" with quite a strange behaviour (I've read the story about the headlights...). This forum here is much more technical. So you're in good hands here. :)

Thanks for the description of the ALB system. According to the image of the system I'm wondering what happens if the piston in the ALB is faulty and lets air from an empty ALB system into the main brake system ->long pedal stroke. On the other hand the master brake cylinder is leaking (sweating) which has to be addressed. The car has been sitting for more than 10 years...yet the owner has still to decide to wake it up.

[Heineken]

Same experiences for me with that forum. Plus two "wannabe part dealers" with quite a strange behaviour (I've read the story about the headlights...). This forum here is much more technical. So you're in good hands here. :)
That's good to hear :)


Thanks for the description of the ALB system. According to the image of the system I'm wondering what happens if the piston in the ALB is faulty and lets air from an empty ALB system into the main brake system ->long pedal stroke. On the other hand the master brake cylinder is leaking (sweating) which has to be addressed. The car has been sitting for more than 10 years...yet the owner has still to decide to wake it up.
From a sealing point of view it's probably not a good idea to leave one side of the system dry as failing seals could cause one to leak into the other.
The first step would certainly be to fix the master cylinder but as long as he can't decide about it .. :rolleyes:

[goldnsx]

It's his car, so his decision to wake up the whole car...

[Kaz-kzukNA1]

If your NSX is 97 JDM AT, then the VIN is NA1-140*** and you have 2nd gen classic ABS.
The overflow happened while you were driving and triggered the ABS long enough last time. You just parked the car afterwards.
2nd gen ABS package is far better than the original 1st gen spec against the leaky solenoid issue but still, not free from it. It will happen if not exercised regularly.

You may have multiple issues with your ABS.
For sure, the air in the accumulator and possibly, the leaky solenoid.
Hope your accumulator bladder doesn't have pin hole….
At this stage, your ABS pump seemed to be at least operating fine.

Not sure how often you drive your NSX but after you parked the car for many weeks, you may hear the sound of ABS pump just after leaving your garage.
Starting the engine is not enough, one of the rear w/speed sensor (not VSS) must see the pulse over about 5mph before the ABS controller activates the ABS pump.

It depends on how long you parked the car and how bad the solenoid leakage is so there is no single diagnosis method for every scenarios but broadly speaking, if the ABS pump stops in less than 5sec, your leakage is not too bad. The longer the pump runs, the worse the condition is.
If the ABS pump kept running for 120sec, it would trigger the ABS warning light and ABS would be disabled.

Another thing you can do is to check the fluid level of ABS reservoir when you are likely to park the car for many weeks.
If healthy, the fluid level won't increase even by 1mm and stays the same over 3 - 4 weeks.
With very-very leaky solenoid, you will see the fluid level going up in just after 1 week.

If you lost the high pressure nitrogen gas behind the bladder of the accumulator because of pin hole, etc, eventually, the pump won't be able to reach the threshold pressure within 120sec and will trigger the ABS light. There is no cure apart from replacing or re-charging the accumulator.

The problem with the classic ABS is the combination of the way it is controlled (logic/software) and the actual hardware design.

The ABS pump won't kick in until it hits the specified threshold. If you have leaky solenoid but the accumulator pressure just sits above the threshold, you'll start the journey with the ABS reservoir above the max line.

Even a tiny single bubble inside the accumulator will turn into millions of bubbles when passing through the solenoid valve.
Before all of these bubbles disappear, the ABS pump kicks in and push back all these bubbles into the accumulator. Repeat this and you have lots of air inside the accumulator and thus, next time when you trigger the ABS long enough, you will have overflow resulting in fluid coming out of the reservoir cap.

The worst scenario is, if the classic ABS was triggered long enough, you could lose the ABS assist completely resulting in full lock condition until you release the brake pedal.
Asking this to ordinary driver under panic braking condition is almost impossible.

I tested this on the proving ground skid pad and snow covered long down slope.
The ABS kicks in while keeping the foot on the pedal.
You keep pressing on the pedal and there are kick-back so the aerated fluid is getting into the reservoir. Sooner or later, the ABS pump is activated and will force all these aerated fluid back to the accumulator but because you are still applying hard braking, the ABS is still triggered and thus, keep sending the aerated fluid to the reservoir.
You are still applying the brake pressure and the ABS pump keeps sending back the aerated fluid back to the accumulator but because of lots of air inside there, the kick back gets weaker and weaker.
It feels as if the brake pedal getting closer to the floor.
Eventually, your foot force will overcome the full of air accumulator fluid and thus, no more ABS.
This is one of the major reason why I upgraded my classic ABS to the modern one body Bosch style.

You can find the well-known flushing method through danoland website.

However, that method won't flush the piston side of the fluid.
You must activate both the inlet (NC type) and the outlet (NO type) valve simultaneously to get rid of the remaining air in the system.

There are very rare cases of ABS piston failure reported but it can happen.
At least one owner experienced the ABS fluid leaking from the slider piston chamber and leaked outside.

On NSX Prime, the owner reported that the ABS fluid did mixed up with the main brake side resulting in increased master cyl fluid level VS reduced ABS side and vice versa.

Both cases can happen with the failed seal at the slider piston.


Kaz

[Heineken]

Dear Kaz,
Thank you very much for the profound and extensive answer. It's always a pleasure to read your recommendations.
When driving the car in Japan (about every two weeks) I remember that the ABS pump started after leaving the garage (>5 km/h). It shut off about 10 seconds later.
In a single occasion it ran for rather long and caused the ABS lamp to come on (when a dealer drove it get Shaken). Since then the lamp never came on again, even though the short pump runs were still common.
Since the vehicle is registered in Germany pump runs are very rare even though the NSX was driven less than in Japan.

Regarding the flushing procedure, let me check if I got this right:



The Danoland procedure opens the inlet valve only
As a result, the accumulator fluid is pushed directly through the outlet valve into the reservoir.
This cleans the accumulator but air bubbles in chamber C are not affected.
Applying voltage to both the outlet and the inlet valve will cause the inlet valve to open and the outlet valve to close
As a result, the accumulator fluid is pushed into chamber C, lifting the sliding piston.
After removing voltage from inlet and outlet valve the spring of the sliding piston pushes the fluid in chamber C back into the reservoir.
This cleans both the accumulator and chamber C.

Am I correct?

PS: It's probably best to start preparing a loom for the procedure, first.

[Heineken]

A short update: I got in contact with Joe from www.cycleterminal.com and ordered a set of matching connectors (Sumitomo HW90).
The remaining parts to build the corresponding loom have been ordered, too. Arrival of the connectors is expected wihtin 1-2 weeks, the other parts within a few days.

I'll keep you updated on the progress and the result.

[austrian type-r]

Hello! IMO trying to repair the old outdated ABS system is a waste of time and a waste of money if you need to pay labor and parts. Upgrade to the 2000+ digital ABS, you wont regret it. It reacts way faster, its lighter and free from mechanical issues. I converted 4 NSX the past 2 years, it is a job of 5-6h about and can be done at home with some good skills and standard tools. I stock all needed parts for RHD and LHD and it is a plug&play solution. I also sold one System to a German Honda Garage after he saw my car at 2016 NSX club Switzerland October meet.

GoldNSX & Heineken: As for the "wanna be parts dealer" at the German Hondaboard and beeing behavior. I hope you dont refer to me, who ships 1-2 boxes with NSX parts worldwide EVERY DAY! ;) I only know Detlef and me are posting there regulary and a bunch of other people unregulary, so reading your comments here kinda feels addressed to me.

It is the only NSX board with german language, but yes it is not much going on there, but still...somehow usefull for my business and therefore I just transfered some cash to the forum operator to get things sorted. It is a problem of all boards, not only NSX....most things are discussed in Facebook groups nowadays. This is not only a good thing... :(

Heinken: How did you solve your headlights problem with not having the E4 mark? I know not all TUV techs need them, but many. I sold 2 sets the past 2 years for realy high amount. As I remember my set was to expensive for you? What way did you go in the end? I have no problem with the situation back in the days, but you never got back to my PNs and Emails in that time when we communicated. :/

800+ several new oem NSX parts in stock
worlds biggest stocking of used NSX parts
www.nsx-parts.com - ATR racing parts GmbH

thanks
Christian

[Heineken]

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Too bad ..

[goldnsx]

Lol!!!!!!!!!!!!! :)

[Heineken]

First part of the loom has been delivered (connectors are on the way).

We'll be using a 10 A four way switch to activate the inlet solenoids and one additional switch each to activate the outlet valve simultaneously (outlet valve extra).

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All these will be put into a plastic housing and equipped with alligator clips to attach it to the battery.
One single 25 A button and necessary cables will be added to the housing to run the pump.

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As it looks like I'll be working on cables tonight :D

[goldnsx]

One thing I remember is to NOT power the pump for more than x (30?) seconds. Good luck!

[Heineken]

One thing I remember is to NOT power the pump for more than x (30?) seconds. Good luck!

Yep, I'll write that down :)

[Heineken]

I'm OK so far with the result:

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The Box is a bit tight. In case of a second try a bigger one should be used.

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Manual testing was OK and when the ABS connectors are attached it's going to the car.

[ozon02]

interesting topic,please more Pictures

[Heineken]

No problem. I'll keep everyone updated and provide a final summary.

[Heineken]

The connectors arrived and have been attached (thanks to http://cycleTerminal.com for support)

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The functionality was tested with a single connector:
Pushing the joystick into one of its four directions works the same way as the Danoland ABS flush (http://www.danoland.com/nsxgarage/brakes/abs/abs.htm) (open the inlet valve and foamy fluid is pushed from the accumulator directly into the reservoir). That technique works but foamy fluid might still be stuck in the sliding piston area.

When the outlet-extra switch (one for reach connector) on the loom is activated the behaviour is as suggested by Kaz:


Both valves (inlet and outlet) are activated at the same time. In other words: The outlet valve is closed additionally.
Fluid is now pushed from the accumulator into the sliding valve (instead of the reservoir).
When the joystick is released the output valve opens and the inlet valve closes.
Then the spring in the sliding piston pushes the fluid into the reservoir


During testing you could here a click and the sound of fluid flowing through the ABS system but no bubbles in the reservoir.
After the joystick is released, foamy fluid appears in the reservoir. It seems to work as advertised :)

After that was confirmed, the final white plastic piece was attached to the connector-in-test (because changing the pinning is very difficult after attaching it).

Once the other connectors are tested I'll provide the final description and a corresponding video.

[goldnsx]

Looks like a lot of work and fun. :)

[Heineken]

Looks like a lot of work and fun. :)

Thank you very much, it's been a pleasure so far :D
A friends who services the NSX in his areas asked for a copy. He'll receive his when this one is proven to work.

[Heineken]

Once the other connectors are tested I'll provide the final description and a corresponding video.


As promised: http://www.nsxcb.co.uk/showthread.php?15395-ABS-Flush-with-Test-Cable