Possible ABS problem - juddering brakes.

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Guest

Guest
Morning All,
I haven't had a chance to investigate this properly yet, but would be
interested to know if anyone has encountered a similar problem.
Occasionally I have a problem when braking - I apply the brakes and I
get a juddering sensation through the pedal, but very little braking
occurs, then after a second or so the juddering stops and the brakes
work.
The juddering may be down to the ABS trying to work, but not because
any of the wheels are slipping or that I am braking hard.
I get the impression that it is worse if I haven't used the brakes for
a while, but cannot be certain of it. For example, driving out of the
drive, round the corner and then up to the dual carriageway (about
500yrds) it always judders when I stop at the junction.
I'm not getting any ABS warning lights coming on and as far as I can
tell all the sensors are working OK.
My initial thoughts are possible vacuum problems with the servo or the
ABS unit needs bleeding (manuals don't mention much about it).
I'm going to look at it this weekend, but for the time being I have
pulled the ABS fuse.
--
Regards,
Julian Voelcker
Mobile: 07971 540362
Cirencester, United Kingdom
1994 HDJ80, 2.5" OME Lift
 
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Guest

Guest
Julian
Not sure this helps but I had brake problems for a while although my car
doesn't have ABS. Different symptoms to you but anyway here goes. I had
intermittent pulling to the left. Sometimes quite severe and scary. I
checked and replaced everything, pistons etc etc. I checked servo,
repeatedly bled the brakes, replaced fluid more etc etcs... As a last straw
I removed and replaced the final section of brake hose on each front wheel
that travels the short distance to the caliper itself. Bingo. With new front
pads the brakes are amazing. I have yet to test fully loaded but they pull
up really well. I can only think that the pipes, original fit, had somehow
rotted inside or something.
Your symptoms sound more ABS-like but if you have done everything else, ie
pistons, calipers, servo etc the pipes are easy to replace although I cannot
remember if they were =A318.00 each or for a pair...
Jeremy
--
Jeremy Llewellyn-Jones
07831 458 793
 
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Guest

Guest
Julian
Sounds suspiciously like what I had when I first had the truck.
In my case it was crud getting into the air gap between the ABS sensors
and the toothed wheel on a rear hub, causing a poor signal, which made
the ABS computer think that wheel had stopped turning when in fact it
was still moving. I had no ABS warning light at any time.
If it *is* an ABS then you will probably find the following:
- Braking is fine at reasonable speeds until you get down to about 5 -
10 mph.
- At that point you get vibration or juddering of the brake pedal, and
less effective braking
- Eventually when you slow down to (roughly) less than 5mph the brakes
suddenly work OK again.
- Pulling the ABS fuse cures the problem
I didn't fix the problem myself, I had the truck at the Toyota agents on
the principle that their diagnostic computer should have been able to
figure out from the ABS computer what was going on. In fact it didn't
and they eventually got the solution from the Toyota UK technical
department. So I can't give you the fix details, only the general
description of the problem as above.
Again, based on my experience, if you get no pull to left or right when
it judders it is probably a back wheel sensor. A pull would suggest a
front sensor on the opposite side.
It is possible to test the sensor output using the milliamp scale on a
multimeter. You open up a connector by the ABS unit to get at the
leads, jack up the truck, spin the wheels, and compare voltages. I've
got the data somewhere (ex Roman - where are you when we need you?) I
can dig it out if you need it.
Christopher Bell
|
| Morning All,
|
| I haven't had a chance to investigate this properly yet, but
| would be interested to know if anyone has encountered a
| similar problem.
|
| Occasionally I have a problem when braking - I apply the
| brakes and I get a juddering sensation through the pedal, but
| very little braking occurs, then after a second or so the
| juddering stops and the brakes work.
|
| The juddering may be down to the ABS trying to work, but not
| because any of the wheels are slipping or that I am braking hard.
|
| I get the impression that it is worse if I haven't used the
| brakes for a while, but cannot be certain of it. For
| example, driving out of the drive, round the corner and then
| up to the dual carriageway (about
| 500yrds) it always judders when I stop at the junction.
|
| I'm not getting any ABS warning lights coming on and as far
| as I can tell all the sensors are working OK.
|
| My initial thoughts are possible vacuum problems with the
| servo or the ABS unit needs bleeding (manuals don't mention
| much about it).
|
| I'm going to look at it this weekend, but for the time being
| I have pulled the ABS fuse.
| --
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G

Guest

Guest
Hi Jeremy,
Thanks, but I don't think it is that. Your problem sounds like the old
issue with pipes loosing their integrity and 'balooning' so any brake
pressure you apply appears as a baloon/bulge out of the side of the
pipe.
Unfortunately it is one of those things that you need two of you to
check so is often missed/overlooked.
--
Regards,
Julian Voelcker
Mobile: 07971 540362
Cirencester, United Kingdom
1994 HDJ80, 2.5" OME Lift
 
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G

Guest

Guest
Hi Chris,
Sounds like the same thing.
I have been assuming that is isn't crud on the ABS rings because this
normally brings the light on.
The crud issue is an interesting one, espescially with the sensor and
ring for the front brakes being housed in the grease filled knuckle
housing.
I don't recall it pulling, so will check the back ones first and see
how I get on from there.
--
Regards,
Julian Voelcker
Mobile: 07971 540362
Cirencester, United Kingdom
1994 HDJ80, 2.5" OME Lift
 
G

Guest

Guest
Er.. no it wasn't the old ballooning thing. There were three of us checking
the pipes after doing all the other stuff, no ballooning but I decided to
change the pipes anyway. Looked to me to be more like crud and rot inside
the pipe...
Jeremy
On 8/2/06 12:30, "Julian Voelcker" <[Email address removed]> wrote:
 
G

Guest

Guest
Hi Jeremy,
That's surprising, although the balooning is often very hard to actually
detect.
When bleeding, did you get much crud out - this would be the indication of the
rot.
--
Regards,
Julian Voelcker
Mobile: 07971 540362
Cirencester, United Kingdom
1994 HDJ80, 2.5" OME Lift
 
G

Guest

Guest
I blew the pipes out with my Viair portable compressor and it looked like
the brake pipe equivalent of pipe scale. When bleeding the brakes, can't
remember seeing much crud but I expect there was some. Once back from
africa, I put new front pads on and changed fluid as a routine job...I was
slightly on auto pilot and pissed off about being back in Blighty in
winter...
Jeremy
On 8/2/06 15:00, "Julian Voelcker" <[Email address removed]> wrote:
 
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Guest

Guest
I don't blame you, although it's a lovely day out today ;-)
The other thing that I have also seen is rather than a bubble, the pipe
actually extends - the internal braiding seperated from the rubber and
was no longer being held at one end so the pipe just stretched!
--
Regards,
Julian Voelcker
Mobile: 07971 540362
Cirencester, United Kingdom
1994 HDJ80, 2.5" OME Lift
 
G

Guest

Guest
Julian,
I have seen this on one or two cars now. I have never
investigated it fully but I believe it to be the start of rust on the
discs, it also feels and sounds like that. I have seen rust start to
form on steel in less than Two hours. I usually drive for a few yards
with the brakes on lightly and it goes away.
Regards, Clive.
 
G

Guest

Guest
Hi Clive,
Thanks, but I think that Chris has hit it on the head - this is a
mechanically induced juddering rather than the gentle grinding of rusty
disks.
I'll take a look at it over the weekend and will report back.
--
Regards,
Julian Voelcker
Mobile: 07971 540362
Cirencester, United Kingdom
1994 HDJ80, 2.5" OME Lift
 
G

Guest

Guest
Hi Julian
I had similar problem(if not the same :( ) when I bought the
car:Someone told me it was rust on the disks?
I went to toyota and for 1000& they changed the complete exhaust and
the brakes.
After that no more juddering. Sorry - it was not a big help for you-
maybe wanted to say 'Hello'
But it wasn't ABS problem :)
Lubo
1996 HDJ 80
On Feb 8, 2006, at 7:30 PM, Julian Voelcker wrote:
 
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