ABS Unit making pumping noise more frequently....please help

I have a 92 NSX that I drive around 2-3K miles per year. I have noticed ever since I purchased my car around 5 years ago that occassionally when I start up the car and start to drive off with it, a pumping noise comes from the ABS unit. I have had the ABS unit flushed a couple of times and the noise still comes on every once in awhile. Recently I brought my car to Don's Hilltop Auto Service and told him of the problem so he did something to it and I was hoping the problem would be fixed. Now it seems that when I drive the car after sitting around for 7 days or so, the pump goes on alot more frequently. I even tried to do some hard braking and locking up the abs every time I drive and this noise still happens.
Is there anything else that I can do to eliminate this noise/problem? I track my car once or twice a year and want to make sure everything is reliable. Does this mean that I have to spend some big bucks and change to a brand new or rebuilt abs unit? Please advise.

It sounds like you may have some sticky valves. If multiple hard braking runs on a wet/sandy surface hasn't cleard the problem, you may indeed need to have the unit repaired/replaced.

That damn noise always happens when I stop at the light and/or while some beautiful woman walks in front of the car admiring it.
Steve

whiteNSXs said:

That damn noise always happens when I stop at the light and/or while some beautiful woman walks in front of the car admiring it.
Steve

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She's too hot, the abs has to pressurize itself! :wink:

It may be that the pump is really not running much more than it ever did but it's just not as quiet as it was when it was new 13 years ago. It might be time to invest in a new pump.

What's the cost of a new abs pump? Is there a way to actually rebuild it? Please advise.

Not sure if this is related but I remember reading that if you lock-up the ABS brakes the next time you start your car the ABS unit can make a short clicking/pumping sound. I have had a clicking sound come from the ABS system on my 98 couple of times, I can confirm that both times this happened I locked the brakes the previous time I had the car out. I will search the forums and see if I can find to post related to this.

I feel your pain!!

I'm dealing with this right now with my 1991;

as a matter of fact, my new (used) ABS assy. is on the way this week.

A few weeks ago I did an EXTENSIVE search b/c of the same issue and didn't really see it explained as well as I'm about to do, so here goes:


As I've been told by Nick E. at Applied Motorsports in Oceanside (NSX ONLY mechanic):

Constant pumping (start/stop) is due to a sticking solenoid inside the ABS system. The pumping noise you hear is, believe it or not, the ABS air pressure pump working perfectly!

It's attempting to fill the ABS sytem with air pressure, but because of the sticking solenoid, the system sensor thinks that the system has only a tiny bit of pressure, but not zero pressure (see end of my reply for why that's important). The pump goes until the sensor just BARELY senses pressure, and stops. But just then, it senses BARELY too little pressure, and it pumps again!! And so on, and so on...


This is generally caused by UNDERUSE of the ABS system over the course of it's life. IOW, the NSX's ABS system is meant to be used frequently, and can get "rusty", so to speak. Your NSX has been babied too much!!


Now the bad news...

Unfortunately, the NSX's ABS system is a closed system, meaning you can't open it up and really work on/replace that solenoid. Bottom line: if you can't get it working again, you have to replace the entire unit, cost new: >$2,200, not including labor

How do you get it working again? Only 2 things you can do:

1) Have your mechanic THOROUGHLY flush your ABS system. There's a SLIM chance there may be a small piece of crud in the system causing the solenoid to stick, and that may work.

2) Excercise the system. You need to go out in some rain or sand (SAFELY, of course) and lock 'em up. A lot. Many times. For a while. And pray that the solenoid un-sticks.

If that doesn't work, than you are unequivocally SOL (As I am!!)

It took me 5 months to find a reasonably priced, used, newer unit by itself (The WHOLE UNIT, not just the modulator). You may find one quicker, but expect to pay no less than $500 for a decent unit. Again, new you're looking at >$2,200. Acura list is around $2,400.

What can you do in the meantime to quiet that embarrassing noise?

Remember, the sensor thinks that there's a LITTLE pressure in the system, but not zero. If it were zero, the pump would pump until it gives up, thinking that there's a system problem. You need to create zero pressure so that after 2 minutes, the pump will at least shut off. The ABS light will go on, but that's fine. I know how you feel, you just want it to stop PERIOD.

The ABS sensor harness is located just to the right of the spare tire and down. You'll have to squeeze your hand in there, but the sensor unplugs if you pull up on it after moving the securing clip to the plug.

I'm sorry I can't give a better description; ask your mech where it is, or if he can just unplug it. You can leave it resting on the connector, but not plugged. It will hang out there while you drive.

This will cause the pump to start pumping upon drive off, and pump constantly for 2-3 mins. Then, when the system recognizes zero pressure, the ABS light will come on, and the pump will stop. This will repeat every time you turn the car off/on, but at least after 2-3 mins while driving, the pump will not pump, and you can drive around without people looking at you.

NOTE: YOU WILL NOT HAVE ABS AT ALL IF YOU DO THIS. BE CAREFUL

Good luck!!

Thanks for the detailed response. I am kind of lucky that the pump only goes on for about 10 seconds or so but occassionally it goes on for what seems like about 30+ seconds. Once I drive the car for awhile, it doesn't usually come back on. It seems to only do this when the car sits around for more than a week at a time.
The thing that worries me is sometimes the brake fluide overflows and drips out of the reservior. That usually happens when the pumps acts up for the 30+ seconds.
I guess I will just keep on doing some hard braking and see if it can fix itself.
Talk about an embarassing moment.

Wow, I don't know about your brake fluid overflowing...

that sounds bad!

I NEVER had anything like that happen, even when my ABS pump was going CRAZY, essentially non-stop pumping...

To my VERY limited understanding, the ABS is a somewhat separate entity from the rest of the brake system.

Can someone confirm this?

I may very well be wrong, but I really think you've got another, separate issue altogether with your brakes, possibly a bad master or slave, most likely brought on by age and lack of use

If that's the case, I would get a tech to check that out ASAP before you go out on a rainy night and exercise your ABS and find out that your brakes are on vacation !!!

You mentioned that you had a tech flush your ABS recently. I would definitely be interested to know why your fluid leaks and if your tech missed something that was wrong with your brakes because he was only concentrating on the ABS portion of the system.

That logic would follow if indeed the ABS and brakes are as separate as I think they are; if you just told him to fix the ABS, he would assume the brakes were otherwise fine, and could easily have missed it. That, however, would indicate a separate problem with the brakes.

Conversely, if the ABS and brakes ARE that much related, then your tech would have to be blind to have missed something such as the leak that you describe!

Point:

1) You either have a different, more serious problem with the brakes;

or 2) Your mechanic may need a new prescription for his specs :tongue: (unless, of course, this leaking began after he worked on it)

back to topic, since your ABS seems have some life left in it (basically the pump's not going NUTS --yet-- ), now's the time to get out and excercise that puppy.

Don't be surprised if it takes a half-hour or more of ABS use to calm this down.

And due to the age of your system and your low mileage driving, expect to have to lock your brakes up EVERY time out, and if you haven't driven it for a couple of weeks, you'll need to pump 'em good for 15 mins +. or so.

REMEMBER: you've got a 13 year old car with an ABS with moving internal parts that sits around a lot. It's no wonder it's worse after 7-14 days of non-use. Lack of use can always lead to deterioration such as this.

I drive mine several times a week, and it happened to me. :wink:

Low mileage sometimes isn't all it's cracked up to be...

Fluid overflow from the reservoir is the classic sign of a stuck selonoid. This is the most common symptom. Flush the system and excercise it as mentioned. You want to be sure when you apply the brakes hard you get the brake pedal to kick back at you. You will feel it in your foot. Get that to happen several times and most of the time this clears it up.

It's attempting to fill the ABS sytem with air pressure, but because of the sticking solenoid, the system sensor thinks that the system has only a tiny bit of pressure, but not zero pressure (see end of my reply for why that's important). The pump goes until the sensor just BARELY senses pressure, and stops. But just then, it senses BARELY too little pressure, and it pumps again!! And so on, and so on...

With due respect, I am not in agreement with above. This is NOT an "air pressure" system at all. You are building fluid pressure. When the fluid pressure gets below a certain amount the pump will come on until the system is up to the proper fluid pressure, then turn off. It is designed to maintain a certian pressure, that is all. (the comments about "BARELY" sensing pressure are just not true) If the pump runs for a certian period of time, 120 seconds to be exact, and pressure is not up to spec, it will shut the pump off, and turn on the ABS indicator. Page 19-29 of the on-line service manual starts the description of the system. It is a good description and worthwhile reading.

The pump running frequently is the sign of the system not holding fluid pressure. This could be a stuck selonoid(likely) or any number of seals in the system, the accumulator, the pump itself, or the pressure sensor. I have had reservoirs overflowing, pumps making noise, ABS indicators on, and have never had to replace an ABS unit yet, not to say it is not possible, but more likely the system just needs to be worked.

HTH,
LarryB

Larry Bastanza said:

Fluid overflow from the reservoir is the ....bla bla bla ...... the system just needs to be worked.

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Had the same thoughts Larry. Reading the manual clears up a lot.
What i wondered though is if someone actually took the whole thing apart yet, and tried to fix it. The seals are only a few quid.
Though stated in the manual NOT to take it apart, Honda gives in the EPC an exploded view, and for all parts partnumbers and pricing.
Apparently there are 2 types off ABS units per the EPC, this is one of them:

I was hoping someone as knowledgeable as Larry would chime in.

I thought I may have been dead wrong...

Perhaps I wasn't given a sufficiently technical explanation by my guys.

I'm only vocal about this topic because I've had the same issue, looked at by 3 techs over 4 months, one of whom is an NSX-only mechanic, and I've excercised the system for HOURS, flushed it, worked it, and no results (pump stll pumps every 5-10 seconds)

The ABS does pulse when being excercised, BTW, so I know something's still alive...

And I have no fluid leaking...

I had to break down and buy a new unit, but maybe I'm an exception to the rule??

Hi Mich!!

Hope all is well with you. I cannot get these parts exploded views from my sources. They only offer the entire unit in the US, best I can tell.

NSXGMS,

Could you explain exactly your problem? You mention pump going on every 5-10 seconds? Do you get an ABS light? You mentioned not having overflow from the reservoir right? Please confirm.

Regards,
LarryB

Larry Bastanza said:

Hi Mich!!

Hope all is well with you. I cannot get these parts exploded views from my sources. They only offer the entire unit in the US, best I can tell.

Regards,
LarryB

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Hi Larry, everything 'about' oke here, hope everything is oke with you to.

My ABS is still oke, though it cycle's sometimes, but thats oke. At least i know the system works
If it completely fails, i will try to take the lot apart, an replace them seals.
Find it wierd though that no one has opened it up and tried it yet.

Mich

NSXGMS said:

I was hoping someone as knowledgeable as Larry would chime in.

I thought I may have been dead wrong...

Perhaps I wasn't given a sufficiently technical explanation by my guys.

Click to expand...

Like Larry, Nick is one of the best NSX mechanics around. I'm sure that if you printed out this topic and showed it to him, he would be able to explain to you the difference (if any) between what he (Nick) previously said to you, and the way Larry explained it.

Thanks, Ken and Larry,

I'm sure I misunderstood Nick,

perhaps he didn't give as technical an explanation as I thought he did and my mind filled in the blanks :redface:

Larry, regarding my problem:

My pump began cycling out of the blue after about 8 mos. of ownership. It would pump for 5-8 sec., then stop. Then do it maybe once or twice more within about 2 mins. of initial cold drive-off. This would happen maybe 2 out of every 5 cold drive-offs.

I had no idea what was wrong, but it was really loud and sounded like something I needed to have looked at. I took it to a very close friend whose Honda/Acura shop is three blocks from my house, for convenience's sake. (he does NOT do many NSX's, if any)

He explained the ABS pump was the noise, and briefly touched on a stuck solenoid. He said he would flush the system, and see what happens, saying it could be some crud. He also suggested that I excercise the ABS regularly.
Once he flushed it, NO pump cycling for about a week. I thought everything was great, problem solved. Then it came back with fury. One day, cold drive-off, and the pump would pump for 5-8 sec, then stop. Silence for 3-5 sec, then pump, and on and on.

I then proceeded to excercise the ABS like crazy. We had a rainy week, so I locked the brakes up for nearly an hour, 5 days in a row, and it did not help AT ALL.

At that point, I broke down and took it to Nick at Applied Motorsports.

He said, he'd do what he could, flush it as much as he could, but said that a new ABS was VERY likely if that didn't work. He also suggested more excercising of the ABS, but I told him I had done as much as I could.

After he had it for a few days, doing everything he could, he told me that it had been slightly better after he test drove it, saying that it would cylcle still, but not as much. He also told me to just unplug the sensor harness so the pump would just give up after a while and at least stop so I could drive it.

I pulled out of Nick's shop, and it was NO BETTER than the day it went in.

So, after 4 months of keeping an eye out, I just bought a '94 unit off a guy for $500. Hopefully, this cures it.

Thanks for the help!

G

Isn't the pump different in a '94 as compared to a 91-92 or is it 91-93?

DutchBlackNsx said:

Had the same thoughts Larry. Reading the manual clears up a lot.
What i wondered though is if someone actually took the whole thing apart yet, and tried to fix it. The seals are only a few quid.
Though stated in the manual NOT to take it apart, Honda gives in the EPC an exploded view, and for all parts partnumbers and pricing.
Apparently there are 2 types off ABS units per the EPC, this is one of them:

Click to expand...

Brian? Ready to start another rebuild / exchange service :biggrin:

A little info here too: www.danoland.com/nsxgarage/brakes/abs/abs.htm

You could also have an accumulator problem (air leak) and therefore the system is not able to hold pressure for any length of time.

Good luck,

DanO

NSXBill2 Isn't the pump different in a '94 as compared to a 91-92 or is it 91-93?

Click to expand...

Can someone indeed confirm this?

Larry?

OK, Now you guys have made me dig a little.

Here is the story:

ABS Modulator Year

57110-SL0-A02 1991-1992
57110-SL0-A03 1991-1996
57110-SL0-L01 1997-1999
57110-SL0-Z02 2000-2001
57110-SL0-Z03 2002-2005

So in 1993 there was a change, but it is applicable for 1991 models on. If you purchased it new the A03 would be all you could get anyway. So using a 1994 pump in an earlier car is fine.

HTH,
LarryB

NSXBill2 said:

Brian? Ready to start another rebuild / exchange service :biggrin:

Click to expand...

Just need to quit my regular job first. :smile:

I'd checking into replacing the accumulator before replacing the module.

I would have to agree with DanO.

DanO, do you know of a way to test the Accumulator? I was wondering if it is like most bladder systems, if it has fluid in it after removal, could it be ruptured? The service manual really only mentions disposal of it. Ther is a seal on the top of it, then two seals for the pressure switch.

I would think you would see brake fluid running down the side of the accululator if these seals were leaking.

HTH,
LarryB