Solve The Brakes Mystery!

abs
brakes
sable

#1

My automotive mystery reads like an Agatha Christie thriller…minus the thrills but - in Minnesota - plenty of sub-zero chills. The plot: during every winter in the Northland, we get snow and ice on the roads. And the brakes on my 2003 Sable are dangerously ineffective (although fine on dry pavement). When applied, the pedal slowly pushes back a couple times, then grinds and finally bottoms out. Even driving under 10mph, applying the brakes gets me into a longer skid than the gradual stop I get not using them at all! The clues: first, the ABS icon on the dash doesn’t light up and it is not a burned out bulb; thus, “Inspector” Mechanic can’t generate a simple diagnostic code. Second, I don’t know if I EVER feel the tell-tale “pulse” of ABS under any conditions. Solve this: what’s malfunctioning in my brakes or ABS (and perhaps exacerbated during snow/ice conditions) that would not trigger the related service light? And what needs fixing?! Tthe game is afoot! Signed, - Miffed In Minneapolis :frowning:


#2
Even driving under 10mph, applying the brakes gets me into a longer skid than the gradual stop I get not using them at all!

Clarify, please. That does not make sense. If your brakes failed completely, then your car would stop in exactly as long as it took to stop the car without brakes. So, pressing on the brake pedal should not make your car take longer to stop than not pressing on the brake pedal. Especially since the car won’t ever stop with no brakes unless you put it in neutral because the engine idle will be good for 10-15mph.

When applied, the pedal slowly pushes back a couple times, then grinds and finally bottoms out.

Please clarify this as well. What exactly is your foot doing while your pedal is dancing around? What does “grinds” mean? The pedal pulsates, or you hear a grinding noise coming from the actual brakes?

What kind of tires do you have on the car? How old are they? How many miles are on them? Honestly, because you say your brakes work fine on dry pavement, it just sounds like you’re sliding on ice which is what all cars will do. ABS is not “magic traction” that suddenly gives your car the ability to stop as fast on ice as it does on dry pavement.


#3

Like Shadowfax, I would like clarification of the issues that were mentioned.

However, I also have to say that I think that the OP’s ABS may be working.
The “feel” of the brake pedal and the sound of ABS activating can be a bit different from one make/model of car to another, but if he is hearing a “grinding” sound and if he feels the pedal pushing back, I think that he is likely hearing/experiencing ABS.

And, as Shadowfax notes, ABS will not give you the ability to defy the laws of physics when it comes to traction. ABS is designed to allow you to steer the car while applying maximum brake force. It is not designed to stop your car in a shorter distance than is allowed by the coefficient of friction.


#4

I also wonder if this grinding is simply the normal ABS action. When this happens, does the car continue in a straight line? Can you steer as you’re slowing?


#5

You’ve uncovered the great farce of ABS. On icy surfaces, you’d better have good winter tires or it will impair your ability stop, sometimes make stopping almost impossible. I discovered this years ago myself.

As already stated, contrary to popular belief ABS is not designed to shorten stopping distances, only to allow you to continue steering. The assumption is that there’ll be someplace to steer TO!


#6

Dear ShadowFax, VDCdriver, lion9car, and mountainbike…

Thanks so much for responding to my query in such a timely and spirited fashion! Pardon my delay in follow-up. What we’re talking about is high priority as a serious winter safety issue. I also allowed myself to get sidetracked with academia and other things. I hope to be more timely.

Shadowfax: (I remember that as the name of a fusion jazz band in the late 80’s!) Let me be both more conservative and precise in my description. If I were driving slowly down a snowy/icy street at a speed of <5mph, hitting the breaks generates such a slide (essentially extending the distance of a stop) than it would come to a stop more quickly than if I were to simply remove my foot from the accelerator. With snow or ice underneath, it will typically not coast and will stop more quickly than hitting the brakes. It is the slide and extension of stopping distance that makes this issue both difficult to describe and dangerous to negotiate.

While the brake slowly kicks back a couple times before bottoming out, my foot is pushing hard on the break with the intent that application will apply breaking power. Really, no different than what a regular foot does when breaking in a tough situation; firm, steady pressure. Let me take another shot at the other component of my description. There is no pulsing. The break pushes up and back slowly but powerfully from the fully applied position. After about the second kick-back, the break pedal bottoms out. The grinding noise (I don’t know what from) occurs through the time the brakes are applied. I relate “pulsing” with a more steady, reliable, and subtle pulse that can be felt through the brakes. Indeed, it is how I have experienced other ABS brakes. In that regard, I am not speaking as someone who is unfamiliar with the feel of that. What perplexes me is your thought that because I am having this breaking experience, I have a magical notion of what these brakes should be doing. I am not saying they can thwart a skid. I am not saying they increase traction. What I am saying, though, is I have never experienced brakes, even manual brakes, that have made the process of breaking more dangerous, less predictable, and atypical in feeling. All cars will slide on ice in one scenario or another. But that doesn’t mean that the brakes are a primary driver in that slide occurring in the first place. And that is what I am describing here. Almost no stopping power in anything other than dry pavement and/or some rain (wouldn’t test it, though)…poor to no stopping in icy and snowy conditions. I understand your question about my tires but that isn’t the factor here. Recent, good tread, all season. Anything more would be a snow tire. A majority of people don’t have them here and do perfectly fine under the same conditions.

I hope the details will illuminate. The difficulty is in trying to explain weird things in a way that makes sense…when maybe no one else has experienced them under the same conditions. And what I’m saying, in part, is that it’s all difficult to follow because something isn’t working right.

I got one mechanics opinion on all this. My entry here is long so I’ll mention it in another. Thanks.


#7

VCD: Thanks for including your voice. I am not suggesting that ABS should defy the laws of physics here. I think it’s easier to say “Hey, this guy just has unreasonable expectations of ABS”, rather than say “Okay, lets assume the guy knows enough to identify that something here is wrong. That being the case, how would something be wrong without the check ABS light going bananas.” And here is what one mechanic concluded. Agree or disagree, this was the feedback I got…

The ABS is not working. During his drive on dry pavement this fall, he reported not feeling the ABS at all. Barring a burn out of the light or an electrical issue with the connection from the sensors to the check brakes light, it was his sense that the master brake cylinder needed to be replaced. Further, if I understood him correctly, he said this is one malfunction that would not set off the check ABS light. I am assuming the reasoning here was - perhaps - because there are no sensors that read something like that. I may be wrong on this point but the general outline I’m expressing here is what he had to say. He wasn’t pushing product or services on me. Does good work, charges reasonably, and will let me use my own parts. But that doesn’t mean that his diagnosis was correct. I welcome any thoughts as to whether this explanation sounds feasible. Thanks, VCD


#8

lion9car: Thanks for jumping into the melee! Okay, yours is a good question. I don’t think it stops in a straight line. But I can test this. I mentioned it earlier, but this is not an even and steady pulse. It is a slow grind, a push back from the brake, and then a total bottom out. I have never experienced something like this with either standard breaks or ABS before, The non-power breaks on my 1992 Toyota Tercel were even better! So, I see where you are going here. But it is no where near anything that I have experienced as normal before. Please see the mechanic’s opinion I included in response to VCD. Thanks again.


#9

Mountainbike: Thanks for the important feedback based upon your winter driving experience. I am not averse to having winter tires. But there are a couple problems with that argument. If it were just a matter of a perfect storm “ABS + non-winter tires = sure problems”, just about everyone I know with ABS and no winter tires (a majority) would be in danger and reporting a similar experience as I. Now, I’m not saying that folks here don’t slide in bad weather or when the roads are icy. But I know of no one else who reports the kind of “performance” and symptoms that I do. I know of no one else having breaks that respond (or don’t respond) in this way. I won’t rule tires out for traction but it would still not rule out the behavior of my brakes, the bottoming out, the grind, the absolute lack of stopping power with no sense that the breaks are doing anything other than exacerbating the slide.

Gents, again, thanks for taking the time to take an interest. I look forward to the clarification and resolution of this issue; either here or in a garage. I hear its going to take me about $130 just to run the diagnostic (with no ABS light going off to begin with!) so I just wanted to explore other situations that might not be identified by this computer “check up”. Thanks, mountainbike. Enjoying a warmer climate now?


#10

I measured the snow in my driveway from yesterday’s storm… 14". But yeah, it is nice to see the days getting longer and average temps climbing. Thanks for the thought.

Your follow up posts do provide far more detail and a far better description. With this added detail this does not sound like an ABS problem. ABS has a wheel speed sensor at each wheel and a solenoid-operated valve in each brake line. If the computer detects that one wheel has stopped turning, it activates the valve with a square wave, which pulsates and closes the line in an intermittent manner. While the closing of the valve can have the effect of feeling like it’s pushing back, it cannot allow the pedal to sink to the floor.

The only thing other than a leak that can allow the pedal to bottom out is a bad master cylinder (MC). Since that seems to be pushing back first, I’m wondering if the piston seal (O ring) in the MC is sticking in the cylinder, then letting go and allowing the fluid to pass by it, allowing the pedal to sink to the floor.

In short, I’m now very strongly inclined to believe you need a new MC. I’d bet lunch on it.

By the way, it’s pretty impossible to get the ABS to activate in a Sable on dry pavement. The brakes are perfectly safe, but not capable of locking the wheels up on dry pavement. Not unless your tires are shot and your legs strong.


#11

Mountain bike,

Thanks very much for the kind follow up. Typing on my phone so pardon brevity. Great and very specific feedback. Will also verify that bottoming out is not just a lower than average stop point for my brakes. It really is my experience that it is a full bottom out but want to duplicate conditions and test. Having said all that, I think you are on to something here and I’ll investigate furrher with your great insight. Do you not feel ABS on dry surfaces in more sudden or emergency type braking at all? Man, I sure have. Quick, efficienr pulses that could be lightly felt through the break pedal when using. Is your ezperience of this different? Thanks again!


#12

It depends on the individual car as to whether you’re able to lock the wheels with the brakes, Different pads, different tires, and different pavement all make a difference. But on a Sable you’d really have to try.

You won’t generally feel the ABS when braking on a paved surface. The computer only activates a solenoid to pulsate a line’s hydraulic pressure if it detects that a wheel has stopped turning, like if it were on ice or sand. In an emergency situation, however, you may press the brakes hard enough to cause a wheel to slip on a bit of sand, a painted line, or something else. In that case the system will detect the slipping, activate the solenoid, and you will feel the pulsing.

Based no your post details, however, I suspect the master cylinder and not the ABS.


#13

Thanks! I can also Google this but is the master cylinder the device that governs the activation of rhe ABS? Oh, one more thing. In a brief experiment, I hit the brakes in a slow reverse. Much different experience- seemingly none of rhe other symptoms.Rhe braking had better traction and stopped by without the symptoms I described earlier. Will keep experimenting. Peace!


#14

I agree with the same mountainbike: The master cylinder is the likely culprit.

Shadowfax is the name of Gandalf’s horse.


#15

No, the MC does not govern the activation of the ABS system. The MC is simply a sealed chamber with pistons in it, that when you press the brake pedal the pistons push hydraulic fluid (brake fluid) to similar piston and chamber assemblies in the four corners of the car, called “calipers” or “brake cylinders” (for drum brakes). The pressure from the fluid, transferred from the master cylinder, causes the brakes to stop the wheels from rolling by pushing pads against a rotating frictional surface, a disc or drum.

The ABS “modulator” is a sealed chamber added to the middle of the brake lines and it contains the solenoid operated valves that open and close in response to the signal from the car’s computer, which sends that signal when it receives from a wheel speed sensor a sign that a wheel has stopped turning (is slipping). It is that pulsating pressure in the brake line that you feel as a pulsation in the brake pedal.

The master cylinder and the ABS system “join”, for lack of a better term, in the middle of the brake lines. The MC in no way governs the ABS system.


#16

Very Intresting discussion going on. Thanks for sharing.


#17

And the plot thickens!..

Hey Northwood, NYBo, and especially Mountainbike, thanks for an intelligent, thoughtful, and very helpful discussion. It is giving me an education on car basics and I appreciate it! Here are the latest developments. They may or may not influence your current thoughts but I wanted to let you know…

My mechanic tells me, after running a computer diagnostic, that nothing is coming up. I did more braking while in reverse and that altered my original impression. It, too, did the pushback, sliding, and bottoming out (though, on occasion, it would stop more decisively) that the front breaking did. When making stops on an icy surface, my car actually skids less (and less out of control) if I hit the brakes far more gently. This still means longer travel before coming to a full and complete stop. However, It doesn’t slip into a skid that lacks control.

Spoke to a car savvy guy, Mountainbike. He says if the master cylinder were not working properly, then my check brake light would be on in the dash. Is it your understanding that a sensor would not pick this up a bad MC? This is one of the reasons, in my initial post, that I asked if their were any scenarios in which something would be wrong but the brake/ABS light wouldn’t pick it up


#18

One more thing to add…

One of the things that has been helpful about this discussion is that it has inspired me to set aside the stress and emotion of frustration that has accumulated over several winters of this befuddling and dangerous braking dynamic. Instead, I am testing my own descriptions for accuracy and precision. In that regard, I wanted to say more about what I have referred to as the brake pedal fade and “bottoming out”. I can’t really measure distance while breaking for precision in inches. But suffice it to say, the brake pedal is not ending flush with the floor. To be very specific, I can slip the front of a low profile shoe between the floor and the pedal. That’s still a fair distance to go without a clean stop. But I want to make sure I am not using an inaccurate use of the phrase “bottoming out”. If it needs to up against the floor, it’s not. If it gets fairly close, it is.

Again, I am very appreciative of those of you who have taken the time to read all this, and those who have read and responded. I hope that I’m not the only one reaping the rewards of this discussion. But if I am, I’m good with that, too!


#19

@LightRadiant

I question the intelligence of the guy that told you a bad master cylinder always leads to a “check brakes” light

he is wrong

Almost all of the cars I work on have ABS

I’ve replaced a few faulty brake masters over the years . . . and most of them didn’t cause any “check brakes” light to come on

I suspect this “car savvy” guy is all talk


#20

@db4690

Thanks for joining the fray! This is exactly what I have been asking about and several people outside this site have expressed that unless it’s a warning light or a code that can be read with a computer, then nothing is wrong. I say, “No, something is off” and it’s as if I’m imagining things :wink: And what you are saying is exactly what the mechanic told me that I referenced much earlier in this string. Three questions: 1) Does a bad master cylinder in turn lessen the performance of ABS, even if they are separate systems? 2) When you are “diagnosing” a vehicle, what symptoms do you see/feel/hear such that you know “Yeah, this car needs a new master cylinder”? 3) Lastly, if the ABS itself is not working properly, would that definitely show up as a “check ABS” light? Between you and mountainbike and all the other kind folks, I’m getting one heck of an automotive education :slight_smile: