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

[DanO]

Hi Larry

I don’t know of a way to test the accumulator but I think you are right, that it is a bladder-type pressure system.

Edit: (Please disregard the rest of this post, the info is wrong)

It seems to me that the problem here is on the AIR side of the system (pump, accumulator); it is losing pressure. There is no air in the hydraulic module (one would hope) so why replace the module? In the past, I have replaced both my pump and accumulator but don’t remember the particulars anymore. What I’m trying to get at here is that there are two problems the ABS can have: hydraulic and air.

Hydraulic problems seem to manifest themselves in the module and will involve erratic ABS functioning, foaming or ejection of brake fluid at the reservoir and typically the yellow ABS light on the dash. Problem = MODULE.

Air problems seem to involve the pump running more than it should, otherwise the system functions normally. Problem = PUMP and/or ACCUMULATOR

That’s my .02 worth,

DanO

 

[Larry Bastanza]

Hi DanO,

Thanks for the comments. I noticed you used "air" in your discussion as well as above, which I did not agree with. Are you certain there is air pressure? After reading the description of the system they specifically talk about fluid pressure. So please straighten me out if my comments above are not correct. Page 19-34 in the manual is where I interpreted my info about the pump and entire system being fluid only.

I am thinking the system is just like my hot water system or well(as in water supply) in my home. There is an air bladder, it's a big blue tank with a bladder inside it(in the cars' case nitrogen/accumulator) and that is making up for fluid pressure drops(or surges), when the system is active, just like when I turn on a facet or flush at home.

I know when my well tank went bad it was full of water, instead of air, since it actually broke, so I am thinking if you remove the accumulator and it is full of brake fluid, instead of nitrogen, it is toast.

Funny, a plumber friend of mine, said: "Kick the bluetank, if it does not move it is bad, if is was good it would be full of air and move easily when you kick it". Damn was that baby heavy to move out and replace.

Thanks,
LarryB

 

[rbirling]

You're both right. The accumulator is just a sphere separated with a bladder. There is high pressure nitrogen on one side, and fluid on the other. The pump pumps in fluid, which raises the pressure of the fluid and the "air". The pressures are the same, since it's a flexible bladder. (I'm reading up on hydraulic components for another project.)

If all the air leaks out, you should get high pressure immediately, and the pump would only pump a really short time, since the fluid itself is not compressible. If some of it had leaked out, I imagine it would pump for a shorter time, more often. If there was a fluid leak somewhere (like a leaking solenoid?), it should pump for the same amount of time each time, but do it more often.

It would be great if you could measure or repressurize the accumulator, but looking at the manual, this doesn't look possible. This is probably by design for safety and liability reasons. But as long as the system pumps and shuts off normally, and the abs works, I'd doubt you have an accumulator problem, unless it's just lost some of the nitrogen over time as mentioned above.

That's my 2 cents while sitting here thinking about it.

Hi DanO,

Thanks for the comments. I noticed you used "air" in your discussion as well as above, which I did not agree with. Are you certain there is air pressure? After reading the
....

 

[DanO]

I noticed you used "air" in your discussion as well as above, which I did not agree with.

Thanks Larry, you are correct as usual. The pump pumps fluid, not air. Please disregard what I said about “Air” above (I’ll try to edit the post). If there were a leak in the bladder then it seems that the pump would run significantly, the reservoir of fluid would be low and the ABS would not function well. But, if there were a small leak on the air side of the bladder then the pump would need to pressurize more often.

That’s a funny story about your water tank. I remember trying to pressurize my parent’s failing water tank with a bicycle pump one night.

DanO

 

[merex]

Just to chime in and join the club

I am having the same problem. I have not flushed the ABS system yet which is the least expensive option. Well...other than playing 'lock-em-up' to exercise the system.

 

[Litespeeds]

Thanks for the technical evaluation of the ABS unit Larry and DanO. So if it is a leak in the bladder or accumulator, are there parts that I can buy to have them replaced so I don't need to replace the entire ABS unit? Please advise. Thanks.

 

[CKS Papa]

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

Did it ??

 

[NSXGMS]

just came in today...will update...can't see how it won't cure it unless the unit is defective.

I'm not sure myself if it's just the accumulator or both the accumulator and pump...pump is quite loud, but not sure if that's a byproduct of hardly any fluid pressure.

G

 

[NSXGMS]

Well, just installed new ABS unit and the silence is music to my ears. Everything works perfectly, no pumping noise at all, even upon start-up. Very faint pumping after ABS is active, can hardly hear it.

I'll be sure to excercise my ABS regularly these days! As a new unit is $2,200 +, I feel I got a relative bargain for $500 for a 1994 unit. $175 for the install here at Hontech in SD.

As long as this unit is excercised from time to time, from what I've learned through this whole experience, I should never have this problem again. As it was, I was apparently one of the rare, extreme cases who had to resort to actually replacing the unit. According to Larry B, he's seen this problem myriad times and claimed he has NEVER had to actually replace a full unit , so I knew I had to replace it, and this used unit seems like it will be just fine.

 

[drew]

(revive)

Anybody figure out how to test the accumulator?

Symptoms:
1.ABS light on after 120 seconds of pump starting, every time
2. Bled and replaced brake fluid--no problems noted, I do this about every two years.
3. I pulled each ALB connector and powered up the solinoid multi times and each one "thumped" as expected (I did not run the pump)
4. A few (~5) rounds of exercise (brake stomp) and pump cycling did nothing, the brakes pulsed but weakly. Lots of tire smoke though.
5. Fluid is clear and no bubbles.
6. The pump is very quiet when running, not the CLACK CLACK CLACK that I remember before
7. This all started with the car not moving for about 90 days.

So I think I'm down to "low pressure"...either a weak pump or accumulator??

Comments?

Drew

 

[Briank]

If the accumulator is bad you will get short pumping cycles, if the pump runs for 120sec and times out then either the pump is bad or a valve is leaking.

 

[AndyH]

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!!

I have been waiting for socal to rain sometime so I can practice my ABS.
In the mean time, I just unplug one of the 20A fuse in the fuse box and the noise still went away.

 

[menuserve]

its crazy... but the abs modulator costs $2500+

the pumping/ticking noise is the unit trying to build up pressure. when the valves (solenoids) either stick or leak the modulator can not build up the needed pressure so you hear this noise as it tries...

after a few minutes the noise goes away... not because the pressure built up but because its a safety feature so the pump doesn't burn out.

it might be possible to unstick the valves, but if not replace then.

or just live without abs!

 

[EndlessNSX]

Bump for some good info here. Great stuff guys...:smile:

 

[NSXGMS]

This is the numero uno thread for this problem...it should almost be a sticky.

2 years later and my used ABS assy is still holding up like a champ. Soooo glad I went used. :wink:

 

[Minch]

Hello guys,

I trying to find out if the later models of the ABS Modulator are a different size or not. Does anyone have a photo of a 2000 onward modulator?

Larry Bastanza wrote:

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

I'm just wondering if a US part might fit my UK car? Honda UK are not exactly helpful when it comes to the NSX as there aren't many here (only around 500 sold here). Can anyone help?

Many thanks
Nathan
(aka Minch)

 

[EK4 hatchback]

Hello guys,

I trying to find out if the later models of the ABS Modulator are a different size or not. Does anyone have a photo of a 2000 onward modulator?

Larry Bastanza wrote:

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

I'm just wondering if a US part might fit my UK car? Honda UK are not exactly helpful when it comes to the NSX as there aren't many here (only around 500 sold here). Can anyone help?

Many thanks
Nathan
(aka Minch)

They won't fit!! You have to get the RHD ABS units.

 

[Minch]

:frown:

 

[cfra7]

I had the same problem at 150K miles. Pulled the fuse so that I wouldn’t have to hear the sound again. Now the light comes on after 30 seconds but no sound. Of course, I no longer have ABS but it wasn’t something I needed in my previous 20 years of driving, so I probably don’t need it now.

The fact that my NSX is only worth around $18K also made the decision real easy. I’m not spending more than 10% of the cars value just to have something I don’t really need. Those with more valuable NSXs will have a more difficult decision.

 

[TurboLexus]

I had the same problem at 150K miles. Pulled the fuse so that I wouldn’t have to hear the sound again. Now the light comes on after 30 seconds but no sound. Of course, I no longer have ABS but it wasn’t something I needed in my previous 20 years of driving, so I probably don’t need it now.

The fact that my NSX is only worth around $18K also made the decision real easy. I’m not spending more than 10% of the cars value just to have something I don’t really need. Those with more valuable NSXs will have a more difficult decision.

Make sense...I mean, who wants to stop in a shorter distance?

 

[summersky1984]

Hi, I had this problem today where the abs is making noise and a lot of brake fluid came/leak off from the top of the abs reservoir cap, what do you guys mean by "exercise" the brake when it's raining?

- - - Updated - - -

what are the steps I should do do "exercise" when raining? thanks for your help.

 

[NSXGMS]

Hi, I had this problem today where the abs is making noise and a lot of brake fluid came/leak off from the top of the abs reservoir cap, what do you guys mean by "exercise" the brake when it's raining?

- - - Updated - - -

what are the steps I should do do "exercise" when raining? thanks for your help.

I'm not sure exercising your ABS is going to help you at this point...a new ABS unit sounds like it might be in your near future. :frown:

Is the ABS making a pumping noise at frequent intervals? That indicates a bladder leak. Not only does it sound horrible and is annoying it reduces the amount of pressure available to the ABS making it less effective and safe when it does engage.

To answer your question however "exercising" the ABS simply means using it by intentionally locking your brakes up from time to time. This is generally easier to do in wet conditions. Remember to do this in a safe place e.g. a large parking lot. Using the ABS once or twice a month should help delay or prevent any atrophy, so to speak, that the unit can develop from non-use. It's common for most drivers to go many years without ever locking their brakes up and using the ABS. On the NSX the ABS seems to develop issues from long-term non-use.

 

[tof]

I have had good luck draining the reservoir with a turkey baster, refilling with clean freshly opened brake fluid, exercising the abs, then repeating the whole process several times until the fluid in the reservoir is clear and free of debris after exercising the system. My ABS pump is currently running more often than I think it should so I will be doing this procedure again soon.

By the way, gravel is the perfect surface to exercise the ABS. You only need to be going 10 or 15 mph to lock up the brakes. Wherever you do it, do it where there is NO traffic and NO roadside hazards.

 

[nis350]

one or more of the solenoids is stuck open and caused the reservoir to over float. Exercising the ABS system will sometimes unstuck (close) the solenoid(s) so that the fluid would stay where it should be. The pump will also stop running as it can now maintain the pressure in the system.

There is a procedure from Dano to manually exercise each of the solenoids. It is fairly simply and effective.

http://www.danoland.com/nsxgarage/brakes/abs/abs.htm

Good luck.

Hi, I had this problem today where the abs is making noise and a lot of brake fluid came/leak off from the top of the abs reservoir cap, what do you guys mean by "exercise" the brake when it's raining?

- - - Updated - - -

what are the steps I should do do "exercise" when raining? thanks for your help.

 

[cmthomson]

ABS pump runs often: an overview

The primary underlying cause of pressure failure in early NSX ABS systems is crap in the reservoir tank fluid. (Crap is a technical term for insect and other airborne debris.) This eventually finds its way down to the solenoid pistons and their O-rings, causing the rings to lose seal. The crap gets into the system because there is a slit in the reservoir lid intended to relieve overflows; sadly that slit is in the airflow from the radiator fan. So if you drive in a place with lots of bugs, especially small ones, you're a candidate for contamination.

Exercising the ABS simply means braking hard enough to cause a skid. The ABS will deploy, which causes all four solenoids to oscillate, which in turn causes the O-rings to scrub themselves, which (almost always) causes the crap to disintegrate into brown goo. Replacing the dark fluid is recommended once it looks like old motor oil.

You can exercise the ABS anywhere that you can skid while braking without getting rear-ended. Wet or gravel roads are recommended to minimize tire wear, but if you don't mind laying down rubber (if you're about to replace the tires anyway), then any wide open road will do; you'll have to go pretty fast. You'll know the ABS has deployed by the distinctive clicking of the solenoids and (usually) shuddering braking, followed after a couple of seconds by the gawd-awful racket of the pump re-pressurizing the system.

A clean system will hold pressure for months (at least). A marginal system will run the pump for a few seconds just after starting the car (and rolling >10 Kmh) every few weeks or even every day. A screwed up system will run the pump for 2 minutes then turn on the ABS dash indicator.

If exercising once doesn't succeed, don't give up. A repeat try (or three) may do the job. Worked for me one time... The only trick here is that you have to skid before the ABS indicator comes on (turn the engine off then back on, and within two minutes, accelerate hard, then brake hard; definitely best done on a deserted wet road). Your fluid will probably turn surprisingly dark.

If none of this works, rebuilding or replacing is one option (hard work and/or expensive); pulling the fuse is another.

Read this pdf for much more gory detail on rebuilding. Look at the photos on pages 8 and 9 to see what the crap looks like.
http://www3.telus.net/public/warshan/Cars/NSX/ABS/ACURA NSX ABS mod rebuld_v06.pdf