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Car Forum / Driving, Maintenance, Tuning / Maintenance and Repair / March 2006Brakes - Hard pedal No Stopping - Intermittent But Serious Problem
Recently I was unable to stop my 2000 Avalon with 4 wheel disc brakes and Michelin X-Ice Winter Radial Tires. The speed was 20-25 MPH and the roads were slippery / icy. The temperature was just below freezing and there was fresh snow polished by rush hour traffic on the smooth asphalt road. Up until that point the car has always been braking normally. I get the car inspected by a very competent shop 4 times a year & have all repairs done ASAP. A couple of the rotors were slightly out of round (mild brake pedal pulsing on braking) and were scheduled for replacement the next time I needed brake pads. I'm uncertain if the problem was the icy roads / black ice or some problem with the brakes that suddenly cropped up. Up until that incident the brakes worked fine every time. Right after the incident the brakes also appeared to work fine - but now I'm afraid to have the problem reoccur. I have the car in the shop to have them look for possible problems and I am asking this group for suggestions on things I could have the shop check for. I saw a post talking about a faulty power booster & will have the shop check that - along with the vacuum supply to the booster. There were no ABS or other warning lights on the dash & all those bulbs do momentarily self-test when I start the car. I recall in the past hearing and feeling the ABS chatter when I would be braking on slippery roads. This time - as I slid along I did not hear the ABS and I also found the brake pedal to be rock hard and not responsive to me pressing on it. At first I tried using a steady pressure - but the car just sailed along as if I had not hit the brake pedal at all. Then I began 'stomping' on the pedal & still - nothing - no slowdown at all. Very Scarry. All suggestions appreciated. Thanks, Cindy a little slushy ice water on the rotor may perhaps cause this to happen!!  SignatureThere are no words that can be heard unless someone listens.... Remove *flaps* to reply > Recently I was unable to stop my 2000 Avalon with 4 wheel disc brakes > and Michelin X-Ice Winter Radial Tires. The speed was 20-25 MPH and [quoted text clipped - 32 lines] > > Thanks, Cindy I could see what you are suggesting if the car had been driven through a bunch of slush & had not been braked for some time - so the calipers could have been encrusted with ice that would have a chance to re-freeze. In this situation, the car had been sitting all day then driven a few blocks then parked for 1 hour. After that it was driven through rush hour traffic (lots of start / stop) for 1/2 hour prior to the skid. The brakes worked fine up to the point of the skid. > a little slushy ice water on the rotor may perhaps cause this to happen!! What makes you so sure you didn't simply slide on the ice? >I could see what you are suggesting if the car had been driven through > a bunch of slush & had not been braked for some time - so the calipers [quoted text clipped - 7 lines] > >> a little slushy ice water on the rotor may perhaps cause this to happen!! That is possible - and will have to be taken as what happened if I can't find anything wrong with the brakes. In all other past slides on slippery surfaces (until that one) I felt the ABS pulse - but that time I did not. That is why I'm wondering if ABS gets fooled on black or wet ice (if that is what I was sliding on). > That is possible - and will have to be taken as what happened if I > can't find anything wrong with the brakes. [quoted text clipped - 4 lines] > That is why I'm wondering if ABS gets fooled on black or wet ice (if > that is what I was sliding on). They don't call it "anti-stop brakes" for nothing :-/ Its very rare, and software to prevent it is getting better and better, BUT its still possible for ABS to get "fooled" into thinking that the car is stopped when in fact all 4 wheels are sliding. In that rare case, lifting your foot of the brake pedal will release the brakes, let the wheels start rotating again, and let the ABS (hopefully) work normally the next time the brakes are applied. Whether or not this is what happened I do not know. But any other ABS problem should at least set a code that can be read by a diagnostic scanner. A power booster failure will not disable the brakes, but it will dramatically increase the pedal pressure needed to stop. Everyone who drives a car should someday (in a deserted parking lot) coast along with the engine off, tap the brakes 8-10 times to bleed off all the vacuum, and then feel what it is like to stop the car without power assist. >That is possible - and will have to be taken as what happened if I >can't find anything wrong with the brakes. [quoted text clipped - 4 lines] >That is why I'm wondering if ABS gets fooled on black or wet ice (if >that is what I was sliding on). You need traction to brake. If there is no traction, then you can't brake. -------------- Alex >That is possible - and will have to be taken as what happened if I >can't find anything wrong with the brakes. [quoted text clipped - 4 lines] >That is why I'm wondering if ABS gets fooled on black or wet ice (if >that is what I was sliding on). If one wheel has traction the computer is smart enough to know the car is still moving and let the ABS do its job. It is possible to lock all four wheels so that the ABS computer thinks the car is at a stop and does nothing. For all the computer knows you are sitting at a light waiting for it to change when in reality you are sliding toward a bus full of pregnant nuns at 60mph. I sure would have someone check it out just in case of a problem but be prepared to accept the fact that you hit a situation where ABS couldn't help. Steve B. >Recently I was unable to stop my 2000 Avalon with 4 wheel disc brakes >and Michelin X-Ice Winter Radial Tires. The speed was 20-25 MPH and [quoted text clipped - 3 lines] >normally. I get the car inspected by a very competent shop 4 times a >year & have all repairs done ASAP. Exactly what happened? It is quite possible that there was so little traction available that your ABS kicked in and did not apply the brakes because there was no traction. ------------- Alex |
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