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Antilock brakes failing in traffic jams

In the winter, driving around downtown in Minneapolis can be very… interesting, to say the least. The usual 5 minute trip from the highway exit ramp to the parking garage can take an hour. But hey, it’s a job. There’s enough stop and go that I can’t just put it in park, so I’m riding the brake for most of this hour.

It only happens a couple times a year, but every time we get weather, after about 45 minutes of this, my abs warning light comes on and my abs system stops working. (Finding that out was… unpleasant.)

I pull into the garage, leave my car for the shift, and it’s fine on the drive home. Is this normal? What’s happening?

Interesting. Have you ever had the brake fluid flushed and replaced?? I think that would be a good step one. It is possible you are over heating the fluid and the abs system is picking up on this.

I agree with " gsragtop" in general if it’s an old enough car or had moisture introduced into the system. Just some other thoughts… If it’s pretty new, I have seen making frequent starts in slippery weather does more to cause this situation then stopping if you have tradtion control. If your car doesn’t have it, disregard this suggestion and move on to the next post. :=) More babble. If you don’t have traction controll, you may be driving too aggressively still when stopping. Keeping speed down, keeps abs from activating as wheels are allowed to lock at lower speeds. Keeping in lowest gear helps too as well as using better winter tires.

How old is your Focus and how many miles are on it? Brake fluid should be drained and replaced every 3 to 4 years.

The next time this happens, wait until you are fully stopped. Then put your car in Park or Neutral, turn off the engine, and immediately restart it. Perhaps the ABS light will still be lit, but it would not surprise me at all if this action were enough to reset the system and restore ABS function. I do not understand the whys or wherefores but I’ve known it to happen.

It’s an '07 Focus SE with >70k miles on it (73k iirc.) Sorry, should have said that in the first place. The car doesn’t have traction control.

It’s been happening since I got the car in August 2010 (42k at the time.)

I had the brake fluid checked and topped off after the first time it happened. The mechanic said the fluid was clean but the level was a bit low. It didn’t solve the problem though.

Would a full flush/change be the logical next step then?

The next step would be to find a competent mechanic as my guess is something in the ABS sensors is failing, and brace yourself, it may not be a cheap fix. (imho)

IMO, just checking the brake fluid at the reservoir is incomplete. As moisture increases in the brake fluid, it tends to collect around the system’s moving parts, particularly the pistons. If the fluid has never been changed in 60k miles, it could give adequate performance until the now lower boiling point is reached in this area, resulting in ABS failure. I STILL think that a likely problem may be too much moisture elsewhere in the system.
“Would a full flush/change be the logical next step then?” Perhaps. I would have it done at by a brake specialist. Then. if “Barkydog” is correct, you’ll have someone more competent to tell you. You may even find that bleeding at the calipers and refilling may be all that’s needed too.

Move to Florida…It’s a miracle cars operate at all in Minneapolis…

I’d say dirty road grime held on by ice and snow gives the wheel sensors false reading. No wheel speed reading and no abs, not until you park your car for a while and the snow melts.

Well Dave we have some interesting contrasts. There is the theory that the brakes get too hot, causing the brake fluid to boil, and also that the brakes are so cold that ice builds up on the sensors. Others fall back on the ‘duh’ principle – when in doubt, change the brake fluid.

I still say it’s none of the above. Just a temporary glitch in the system. When next it happens, do a quick engine restart to reset the ABS.

Do nothing until you test the reset theory. Whatever the result, check back with us by all means and give us your report.

SteveF…good advice, but the condition is elicited by a particular set of circumstances and not intermittent. IMO, the circumstances, either sensor problems or usage is involved. Bottom line, take it to a brake specialist. I would not get into chain of fixes either when a diagnoss by a competent shop could tell him in a few minutes.

My office’s fleet of Escapes from that time period have lots of ABS problems that are sensor-related. I wouldn’t be surprised if Ford’s ABS design left something to be desired.

The bottom line is that I think you need to do some maintenance here. You’ll need to bring the car to a shop to have the sensors and their respective rings checked out, as there may be crud up in there from the road and that can cause your symptoms, and I’d also suggest that you get the brake fluid flushed and refreshed, not only becaue of moisture (which in your caes can ice up) but also because of crud that can get backed up into the system and affect the function of the individual valves in the ABS modulator. They’re little solenoid operated valves that open & close to control the pressure in the lines. When brakes are worked on, many people simply push the caliper pistons in rather than pushing the fluid out the bleeder and this can drive any crud in the calipers back into the modulator.

In short, I’d suggest that you

  1. have a shop check the ANS sensors and their respective rings, and
  2. have the fluid flushed and refreshed.

Well, many old pros (on Cartalk) don’t think I know anything about cars, but I agree with SteveF.