Squirly Braking...ABS Problem?

[merex]

Here is the problem. I drive in a straight line, I have tried this on a variety of roads, and if I slam on the brakes, hard enough to engage ABS, the LEFT rear end suddenly and quite alarmingly I might add, breaks loose.

Could this be an ABS problem. My tire pressures checked out ok. Could it be from having softer settings on my shocks? I really have no clue, just throwing out blind guesses.

I have noticed that the ABS pump thingie in the front of the car seems to run more often that it used to, which is why my first guess was ABS.

TIA! Any ideas?

Cheers,
Ross

 

[NSX-Racer]

ABS is not ESP so the rear end of the NSX can come loose under heavy braking even when ABS is alright (been there, done that - I even totalled one with that behaviour which is not uncommon for a car with more weight rear than front, has something to do with load transfer during braking).

Don't know which shocks you have (adjustable Konis?). If the front shocks are softer than normal the car would dive more under braking and so the rear is lifted more - the rear tires therefor loose ground contact very early. This effect increases with stickier tires but also when the road has some bumps.

If one of your ABS sensors would be bad you would most likely have an ABS/TCS warning light in the dash.

 

[drew]

Guess:

Your rear calipers are are not releasing as they should. If the LR (LF?) locks up, I believe the car would slide in that direction. The ABS might not be working for the one of the channels and/or the caliper is not responding fast enough to the change in pressure.

You could also have alignment problems: bad suspension bushing or a bad ball joint [somewhere] that is causing things to get out of whack under stress.

Have somebody watch you lock the car up a observe what happens....mark the tires so you can see what is happening easier.

Drew

 

[DanO]

It could be alignment as easy as it could be an ABS issue. Done lots of ABS braking both on/off the track and never had a problem with sudden loss of control, except one time when my alignment was way, WAY out of whack.

DanO

 

[merex]

I feel pretty confident that my alignment is within specs. I just went for a drive and my ABS light came on for a little while then magically turned itself off. So right now I would assume ABS is flaky.

Thanks for the input guys.

 

[DanO]

I feel pretty confident that my alignment is within specs. I just went for a drive and my ABS light came on for a little while then magically turned itself off. So right now I would assume ABS is flaky.

Is the yellow light coming on during braking? Obviously, a yellow indicator light points more towards a ABS problem than an alignment problem. Check around the ABS reservoir for what will look like spilled brake fluid, this is a telltale sign of intermittent solenoid failure.

DanO

 

[MJK]

Did you by chance rebuild the calipers lately (or otherwise introduce air into the system)?

If so, read on. If not, ignore.
When I rebuilt mine, it acted as you described until I tapped/flushed all the air bubbles out. You'd be amazed what even just a LITTLE air does. It took me 3qts to get everything filled and air free. Tap on the caliper with a wrench to dislodge all the little air bubbles and then bleed to get them out of the valve.

As a second question, is the car leaking fluid anywhere?

 

[ATERPAK]

Let's keep this simple gang. First. How long has it been since you've had the ABS system bled? If not within a year, then have it done with a high quality fluid. Believe it or not when you activate the system, it repumps the fluid in the reservoir and this pressure builds up heat. This heat will eventually cause the fluid to break down and that with the water the fluid collects over the year will cause it to foam. This foaming action will often cause the sytem to cause uneven braking, long ABS motor cycling, and even potential failures. Try bleeding the system first and that may solve the problem. If that doesn't solve the problem, you may have other brake issues, such as a sticking caliper, uneven brake line pressure to a caliper or something else to troubleshoot. My guess the ABS bleed will probably solve your problem.

Let us know.

 

[merex]

How long has it been since you've had the ABS system bled?

I can check service records for an exact answer, but I am certain it has been more than a year.

Thanks much ATERPAK for the advice. I think looking for leaks and bleeding the ABS system are my best options.

Another question: Is the ABS a distinct closed system with its own fluid? I think the answer is yes, and if so would it be wise to also bleed the brakes as well?

Thanks for all the help guys. I will post an update in a few days.

Cheers

 

[Larry Bastanza]

Another question: Is the ABS a distinct closed system with its own fluid? I think the answer is yes, and if so would it be wise to also bleed the brakes as well?

"Yes and Yes" especially if it has been over year since either system has had maintenance.

HTH,
LarryB

 

[nsxtasy]

Since you're having problems, and you haven't had the brakes serviced in over a year, I think it would be a good idea to flush the brake fluid (replace it with fresh fluid), rather than merely bleeding (removing air bubbles from the system).

 

[ATERPAK]

Bleeding the brakes and flushing the brakes are really one in the same. Since the whole purpose of doing either is to completely change the fluid and also get rid of any potential air bubbles in either of the systems. :wink:

 

[merex]

I hate my local Acura dealer, however my NSX tech I have used in the past, (headers, clutch, timing belt, shorties, CT R&P) now works for a Honda dealer. Sigh...his bill rate was $55 at the small import shop he left, but it is a tad bit more now

I digress. He should be able to handle the ABS and braking flush at the Honda shop, correct? I seem to recall the service manual mentioning a special tool for the ABS bleed.

 

[drew]

Bleeding the ABS is fun and easy (no really it is).

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


I have the special tool available on a free "mail to the next guy" for about three years now. Made several tours around the country now. It is around here....somewhere... anybody know where? (Al, any ideas?)

Drew