NSX Brake Fluid Problem

slimjim935

slimjim935

Registered Member
Joined
19 June 2009
Messages
48
Location
Austin, Texas
Hey all.... have a little problem with my brake fluid.

I have been struggling for the answer for the last few months because I thought I had a leak but I finally found what the problem was.

I am not as technically savvy as most people on there, but I will do my best explaining it. As many of you know, there is an upper brake fluid chamber(where you put the brake fluid in) and the lower chamber...where is siphons through or whatever.

For some reason every 2-3 weeks my upper chamber loses some of its brake fluid while the lower chamber gains some...it goes WELL over the "max" line and begins to leak. I have to siphon the fluid out of the lower chamber and put it back in the upper. As I said, it takes about 2-3 weeks for the upper to fully empty. I dont know why this is happening.

Has anyone heard of anything similiar? I do not want to have to buy a new ABS module, as im selling the car soon...but im honest and do not want to sell the car with this problem... even though it affects nothing.

Let me know if there is something I could check and figure out the problem. Again... there is NO LEAKS when the fluid is distributed evenly...just over time , one chamber fills completely up and one goes empty.


Here is a pic to show...

see how the upper chamber is not as full as it should be? the lower is OVER the max line... it was 2 weeks ago since i last siphoned some out.

brakefluid.jpg
 
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I have the same problem, But i need to fill the Reserve above the ABS unit up every 2-3 weeks, its a slow leak, doesnt hinder my stopping in anyway, and the ABS works like it should but after Exercising the ABS its leaks bad for a day or so, I am going to upgrade to the SOS ABS soon, so it doesnt really matter to me right now ya know, but I would love to know how to fix it, I know its a common problem for older models like mine (92)
 
Yea man... for me there is NO LEAK unless the lower chamber gets full...then it starts leaking all over.

However its fine and everything runs perfect if the fluid is distributed normal

I have a 1998 btw if that makes any difference
 
I don't believe that the two systems are connected. The upper one is the master cylinder for the brakes, and lower one is for the ABS. If you check behind the carpet near your pedals, you'll notice it's probably coated with brake fluid. Changing out the master cylinder is easy and then you just need to bleed the system.

Next, the ABS resivoir is probably getting high because a solenoid is stuck and the fluid is being displaced. You probably need to exercise the ABS a little more and get it flushed.
 
Yeah only after I exercise my ABS will it leak, or should I keep working it till it stops leaking? I wonder.
 
DocL said:
I don't believe that the two systems are connected.
Click to expand...
I think they are connected, well have to. Looks like the balance between the fluids is mixed up by something but don't know what. The simplest explanation could be that gravity is working here and there's a leak or a link between both systems that should not exist.
Looking generally for visible leaks is a good proposition, getting wrid of the v0.1 ABS system is even better. :wink:
The brake master rarely leaks to the carpet/interior. It mainly leaks at the brake booster (black drum area). If it's leaking quite long you get to know that an NSX CAN rust. :D
 
DocL said:
I don't believe that the two systems are connected. The upper one is the master cylinder for the brakes, and lower one is for the ABS. If you check behind the carpet near your pedals, you'll notice it's probably coated with brake fluid. Changing out the master cylinder is easy and then you just need to bleed the system.

Next, the ABS resivoir is probably getting high because a solenoid is stuck and the fluid is being displaced. You probably need to exercise the ABS a little more and get it flushed.
Click to expand...

Like I said DocL, I don't know enough about the ABS system to make any assumptions...however I do know, nothing behind the carpet is wet and im 100% sure there is no leak. I tested it for a week straight and put white paper underneath my car. It only leaks when the bottom cylinder gets full(way over the max line)

I let it sit overnight after driving it and had 5-10 drops of brake fluid on the ground. I fixed it the next day and drove it and no leaks for the next week till it got full again.


Basically, I havnt added ANY brake fluid in months. I just keep moving it back from the lower chamber...back to the upper chamber. Same brake fluid, just something isnt right


Anyway, thank you guys for trying to help. Hopefully I can figure something out
 
:confused: I don't think the 2 systems are connected in any way. They work independently from each other. If the top reservior is draining fluid check the master cylinder where it goes through the firewall on the interior or the brake calipers/lines for fluid leaks.
 
I stand corrected. There is a feed from the master cylinder to the ABS modulator/Solenoid unit. Why this is happening is strange. You may have a bad seal or proportioning valve in the master cylinder that is allowing fluid to transfer when it shouldn't. Maybe it would be worth it to install a new one. It's an easy DIY.
 
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DocL said:
I stand corrected. There is a feed from the master cylinder to the ABS modulator/Solenoid unit. Why this is happening is strange. You may have a bad seal or proportioning valve in the master cylinder that is allowing fluid to transfer when it shouldn't. Maybe it would be worth it to install a new one. It's an easy DIY.
Click to expand...



A new ABS modulator or a new master cylinder?

I have a great mechanic that is a friend that can do it , but he had no idea what the problem could be either.

thank you DocL for the advice as well
 
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I highly doubt it is the master cylinder. You would have a spongy brake pedal. You did not mention that you did:).

I would review page 19-35/36 of the 1991 service manual and look at how the modulator seals isolate the two systems (main and ABS). I have to say, I have never seen this issue up close and personal, so I cannot offer a concrete confirmed fix. With that said, I suspect you have a bad seal between Chamber "A" and Chamber "C". It looks like the piston has a pair of seals to isolate the fluids.

If this is the case, I would update the system, since the cost will be close for new parts.

HTH,
LarryB
 
Went to the acura dealership,

I was told there was an internal failure of the ABS modulator which was causing the fluid to siphon back and forth incorrectly.

Not sure what that means but they quoted me $3700 for labor/parts for a new ABS modulator


Anyone have any cheaper options of what I should do?


I have been driving like this for 8 months now and they said I could drive like this forever but the fluid would never siphon correctly.

I am selling the car soon but I could not sell it knowing there is a problem. Any opinions please let me know!


Thanks again everyone


Any sites where I could get it cheaper and have the local NSX guy from Raleigh install it?

or the new ABS v2 or whatever? let me know!

thanks
 
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You can try a used ABS system. There are some for sale from those who went to the 99+ system. If you can't find one I have one but I'm in Europe.
A 99+ version is about $1500 without labor. Hard to justify if you sell it. But I agree with you that this has to be fixed as the brakes are important for some reason.
 
goldNSX said:
You can try a used ABS system. There are some for sale from those who went to the 99+ system. If you can't find one I have one but I'm in Europe.
A 99+ version is about $1500 without labor. Hard to justify if you sell it. But I agree with you that this has to be fixed as the brakes are important for some reason.
Click to expand...


Can I use any ABS system from a 98 + NSX?

How much would yours cost (ill pay for shipping as well)

Thanks for all the help man

Can you send me some links of the 99+ version as well? (where i can buy it online)

thanks!
 
slimjim935 said:
Can I use any ABS system from a 98 + NSX?

How much would yours cost (ill pay for shipping as well)

Thanks for all the help man

Can you send me some links of the 99+ version as well? (where i can buy it online)

thanks!
Click to expand...

Chris at Science of Speed sells a conversion kit to upgrade to the second generation ABS. There is a recent thread about the upgrade, including the level of effort (pictures an all).

There are some older, possibly archived threads about 'working' the first generation modulator to flush any debris from the valves in the modulator. I believe 'oldmnnsx' even built a flushing machine that would exercise the solenoids (and valves) while the car is parked.

Miner
 
goldNSX said:
I guess that yes but I'm not sure. Maybe 'our' professionals here can tell.

@Miner: The problem is not flushing the problem are the gaskets Larry Bastanza talked of.

The SOS kit is here: http://www.scienceofspeed.com/produ...ts/NSX/ScienceofSpeed/NA2_ABS_System_Upgrade/

Not cheap if you plan to sell the car.
Click to expand...

I believe the seals that Larry is talking about are the internal valves between chambers. I had the same problem about 5+ years ago. I jumped on the binders hard enough to exercise the system and the problem was resolved. I believe 'oldmnnsx' has been very sucessful extending the service life of 1st generation ABS, which is the same on the first generation Legend, so it dates to the mid to late 80s.

As for the price of the upgrade, one can always sell the car with the upgrade advertised and built into the sale price, and perform the upgrade or repair as part of the sale.

Miner
 
Guys,
This is really weird. Have you checked all of your brake calipers for a possible leak? Look at the inside of your wheels and see if there is an accumulation of dirt/dust coated brake fluid. In order for fluid to get from the brake master cylinder reservoir into the ABS reservoir the fluid pressure would have to exceed the pressure in the ABS modulator. The operating pressure of the ABS unit is 4800 PSI. Have you noticed that the ABS pump has actuated regularly? If you don't know, the pump makes a LOUD ANOYING sound. If the pump was running at a stop light on a 4 lane road everyone around you could hear it. People think that your car is about to BLOW UP! Have you heard that noise? Is the ABS caution light illuminated on the instrument cluster?

If you have an ABS solenoid that is seeping the pump will cycle on a regular schedule. This is more than it should, normally the pump will only actuate after an ABS excersion. The fluid in the reservoir will rise due to the reduction of pressure in the ABS accumulator. The pump will then actuate and re-pressurize the accumulator. The pump actuates at 2800 PSI and then shuts off at 4800 PSI. The accumulator is the gold globe on the bottom rear of the ABS unit about the size of a grapefruit. (There other things in this world the size of a grapefruit too) If pressure drops in the accumulator the amount of fluid stored in the accumulator decreases and so has to go somewhere which is into the reservoir until the reservoir can't hold it and then it overflows and makes a mess.

I think that your brake fluid from your brake master cylinder is either going out a caliper or leaking down the brake booster, but it isn't going into the ABS reservoir. The only way that fluid gets back to the ABS reservoir is through the solenoids. Look at the cutaway picture in the manual.

Sorry I am in Afghanistan or I would be more helpfull. I have extra ABS modulators in my garage that would probably take care of your problem. I won't be home till Oct for leave, sorry.

Brad
 
The brake fluid is definitely going into the ABS chamber. I siphoned it all out again yesterday and the entire ABS chamber was full to the top... I mean to the TOP! I have not put new brake fluid in it months. The master cylinder chamber was so empty that my emergency brake light wouldnt shut off.

But thanks for the help guys. I ordered an almost new ABS v2 system from chris at SoS for $700 + the harness for another $400. He said my problem was somewhat common from 91-99 NSX'S


Alot cheaper then $3700 from the dealership

When I sell the car im just going to tell them whats going on and include the new system so they can decide if they want to install it themselves or let someone else do it.


Thanks again
 
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Jim,
When I was out doing my aircraft pre-flight, yesterday, I thought of something that you may want to try, and save you a LOT of MONEY!

If fluid is moving between brake master and the ABS you could try to see what is causing one of the actuators in the ABS modulator body to leak.

To do this you DON'T need to remove the modulator unit. You DO need to DEPRESSURIZE the ABS unit by using the HONDA T-Handle bleeder tool. Then remove the two covers (three bolts each) that house the ACTUATORS not the SOLENOIDS. The solenoids sit under the reservoir. You may have to remove the reservoir to get at the bolts.

The actuators have different sized springs that sit on top of them (KEEP THEM STRAIGHT). I can't tell any difference between actuators, but keep them straight anyway. I think that you must have either a small particle of contamination under one of the actuator seals or there is a TORN seal lip.

What do you have to lose? It doesn't work now. Take a look at my other threads and comments about the ABS system for help.
Brad
 

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