Modulator rebuild time or bad accumulator?

[Nguyen Nguyen]

Hello,

I recently did a Dan’s solenoid flush on my 92 NSX (90K miles driven about 5 times/year the last 10+ years) to solve the problem of ABS pump running every few minutes. The fluid that came out was clean and everything work as described in Dan’s procedure. Unfortunately the problem didn’t go away during test drive. I think the accumulator is o.k (though I am not sure) since there was pressure to cause fluid flushed back as each solenoid was energized. On first start (after overnight) the pump runs for about 1+ min, then after that during driving, it’d run for a few secs every few minutes. So it seems pressure is leaking somewhere.

Would rebuilding the modulator using Warren’s kit solve this or it’s likely a bad accumulator?

Thank you for your opinion.

Nguyen

 

[asylum]

It seems you have no leak to the outside. I think (someone confirm ?) that the only possible way for the fluid is that it goes from the accumulator to the reservoir via the solenoids. That would mean you have a small leak at a solenoid.

In your garage, I would activate the pump "manualy" to build up max pressure in the accumulator. Note the fluid level in the reservoir. Come back later and see if the level has raised.

If this is the case, there is perhaps still a dirt around the solenoid valve (repeat the solenoid flush) or an o-ring is worn.

 

[Kaz-kzukNA1]

Hi, Nguyen.

After flushing all four solenoids, you will need to pressurise the accumulator by activating the ABS pump manually for 30sec.
Before doing so, did you use fresh fluid or waited long enough so that there was no bubbles sucked back into the accumulator?

After manually activating the ABS pump for 30sec, wait for more than 1 - 2min to cool down the pump.
Activate the pump again for another 15 - 20sec or so but keep listening to the sound of the pump and stop it as soon as the sound started to change.
The reason why I used the word '15 - 20sec or so' is that it will be different for each ABS due to the health of the pump as well as the accumulator.


When you activated the ABS pump for 30sec, did the fluid level drop rapidly?
For example, with healthy system, 30sec is enough to lower the fluid level from MAX level to the MIN line.
If the level didn't change at all or just a few mm drop, your accumulator is punctured or your ABS pump is dead.

Warren's kit is great for fixing the issues around the o-rings.
However, if your leakage is caused by the contamination at the solenoid valve seat, it won't fix your issue as they are all inside of the solenoid body.
There is no easy way telling whether your issue is o-ring or valve seat related or both without opening the system and visually checking it.

You just need keep flushing.

If your fluid level drops rapidly as described above when manually activated the ABS pump for 30sec, at least your ABS pump and accumulator are operational.
If that is the case, then try flushing each solenoids while running the ABS pump.
You need to be careful not to burn the pump but the pulsating pressure while the solenoid is rapidly opened and closed will help washing off the contaminated valve seat area.


Kaz

 

[asylum]

The pump is good enough as it is able to pressurize the accumulator. If pump was not good, it would throw an ALB light after running 1min+ saying pressure did not build up.

Keep flushing with fresh fluid before starting a rebuild...

 

[Nguyen Nguyen]

Hi guys,

So I went through 3 sessions of solenoids flush using a total of 128 oz of brake fluid. When the pump was activated about 30 secs (less), it did lower the fluid level from max to below min. After max pressure was achieved, the fluid level did not rise overnight. So this seems to indicate pump and accumulator are good and perhaps no solenoid leak?

Unfortunately the problem is still there, although has improved. Before any flushing, I would get a warning light after the pump ran for a long time during a drive. After the first solenoid flush session, I didn’t get any more warning light, however each time the pump got activated (every 15-20 secs or so), it took 45-60 sec to stop running. After the second solenoid flush session, the pump still got activated every 15-20 secs or so, but only ran for 5-10 secs. There were no improvement after the third flush session. Note that the pump got activated even when I didn’t touch the brake.

If there is air in the accumulator, would that cause the system to cycle frequently? Does solenoid flushing get rid of air in the system? I could not open the bleeder nipple using a 10mm wrench or a ¾ extension as some people were able to do.

Incidentally on the last solenoid flush session the system might have sucked in air. I did not run the pump enough to fully pressurized the accumulator. As soon as the car was rolling, the pump ran and empty (full when started) the reservoir.

Thanks again.

 

[JoeBEZSLU]

so what was the final solution on the ABS issue?

 

[Nguyen Nguyen]

I Have not have time to work on the problem, car has not been driven.

Nguyen

 

[NSX1145]

Where can the seals be purchased?

 

[SWFL_NSX]

[MENTION=18431]warrenw[/MENTION] put together an o-ring kit that is described in this thread:

http://www.nsxprime.com/forum/showthread.php/162710-ABS-ALB-modulator-rebuild-write-up

Unfortunately he may have discontinued the kit after this last group by.

Hopefully he will keep going, or somebody else will pick up the project. I just fixed my ABS using the kit and am very pleased with it.

 

[warrenw]

I still have kits for '91 - '92 modulators.

 

[warrenw]

Dan was able to create a youtube video on what is required to rebuild the modulator:
https://www.youtube.com/watch?v=NqTzxKum55Q

my original thread from 2012, is now closed, but I still have 0-ring kits available:
http://www.nsxprime.com/forum/showt...ulator-rebuild-write-up?highlight=abs+rebuild

 

[Wavey1]

It's not too hard to pull the accumulator to see if the diaphragm is still intact. From inside/under the LF wheel, pull a few small bolts and disconnect hydraulic line. You can insert a probe with a soft &/or rounded tip and see how far it goes. If you encounter resistance the diaphragm is OK. If it goes all the way through it's ruptured and the accumulator needs to be replaced. They're available new but $$$$$, good used ones are scarce.