Posted by Ike on January 7, 2009, 3:53 am
My '04 has been remarkable - I've never before owned a car so long, and
it's still like new.
About 15-25% of the time, when coming to a full stop with light pedal
pressure there will be a major "grab" in the last foot or two. Toyota
(twice), Firestone (three times), and I (three times) pulled the brakes
apart and could find nothing wrong. The last time I did the work, I
replaced the rear shoes and turned the drums.
However, the phenomenon persists, and is #$%!! annoying. And, of course,
I'm concerned about safety.
If it is not the brakes, it might be the regen mechanism failing to
disengage, or something else in the hybrid system that's breaking.
The car is under an extended warranty (two more years), so I can just
wait for it to solidly break. Or is there another way to get attention
for this problem?
Can you think of diagnostic checks I might do?
Posted by Michael Pardee on January 7, 2009, 12:32 pm
Could it be a lurch as the combustion engine shuts down? That is a common
phenomenon, but it doesn't actually change the braking rate. It doesn't
really match your description of a major "grab" either but I wanted to get
the question out there.
The regen should stop at 11 mph. Does the vehicle have stability control?
That could apply braking to one or more wheels if it goes wrong. I am not
familiar but I think there is a way to disable the stability control so you
can see if that has any effect.
Otherwise, I think the next question is "how many wheels are doing this?"
That could be hard to answer; I hope somebody here will have an idea. Maybe
wrapping each wheel with paper, driving slowly between test stops, and
looking for wear and tear on the paper? My guess is you will have to do some
more identification of the problem (troubleshooting, actually) to get Toyota
Posted by Ike on January 7, 2009, 3:32 pm
Michael Pardee wrote:
It doesn't have anything to do with the engine.
Yes, there's stability control and you're point is well taken. I'll look
for a way to disable it.
As for the "...wheels..." suggestion, identifying 1 or 2 would be
useful. This weekend I'll do a series of stops with an outside observer
right next to each of the wheels. That'll take a while, and of course
intermittent problems never arise when one is testing for them.
Posted by Was Istoben on January 7, 2009, 6:13 pm
It sounds to me as if the problem occurs at the point where the car switches
from regenerative braking to the friction brakes. Perhaps there is
something amiss in the switching process.
Posted by Peter Granzeau on January 7, 2009, 8:15 pm
I'd say brake. My brakes grab coming to a stop after a rain, every
time. My solution is to make one stop from speed (25 or greater) with a
heavy brake foot. That cures the problem until the next time I drive.