bmw e30 "crunchy" brakes

In article <20080512063620.73451fb5.TakeThisOut@privacy.net>, Yvan <me.TakeThisOut@privacy.net> wrote:
>Nedavno dhs napisa:
>
>> My 89 325i has a brake problem I haven't experienced before
>> on any other car. Several times a day, when the brake pedal
>> is depressed it feels (for the lack of a better term) crunchy,
>> a bit like the ABS is kicking in. For those of you who live
>> up north, it feels exactly like stepping on snow that partly
>> melted and then re-froze. This has been going on for several
>> months and seems to be getting more frequent.
>
>I do not know if this is legal / safe, but you could try driving with
>ABS disconnected to find out if it is ABS related.

Safe (and easy/cheap) would be the more important issues, at
least for short-term trouble-shooting. Is this something I can do
myself, or will I need to take it to my mechanic? I'm inclined
to believe that at least one of the two used controller/computers
that I tried was good, so could there still be ABS problems causing
this? Could it be the ABS sensors or the hydraulics?
When I deliberately engage the ABS (jamming on the brakes on
a wet/dusty road), it seems to work normally.

And is this a common problem on E30s? I've searched with
Google, and didn't find any mention of this type of problem.

Thanks,
 >> Stay informed about: bmw e30 "crunchy" brakes 

In article <g084ft$2md$1@jib.cs.utexas.edu>, dhs <dhs.RemoveThis@cs.utexas.edu> wrote:
>My 89 325i has a brake problem I haven't experienced before
>on any other car. Several times a day, when the brake pedal
>is depressed it feels (for the lack of a better term) crunchy,
>a bit like the ABS is kicking in. For those of you who live
>up north, it feels exactly like stepping on snow that partly
>melted and then re-froze. This has been going on for several
>months and seems to be getting more frequent.

It's possible the ABS is kicking in. Pull out the ABS relay and see if
the problem persists. If it still happens, it's an ABS issue. There is
no harm in driving with the ABS disabled for a while if you brake properly.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."
 >> Stay informed about: bmw e30 "crunchy" brakes 

> Safe (and easy/cheap) would be the more important issues, at
> least for short-term trouble-shooting. Is this something I can do
> myself, or will I need to take it to my mechanic? I'm inclined
> to believe that at least one of the two used controller/computers
> that I tried was good, so could there still be ABS problems causing
> this? Could it be the ABS sensors or the hydraulics?
> When I deliberately engage the ABS (jamming on the brakes on
> a wet/dusty road), it seems to work normally.
>
> And is this a common problem on E30s? I've searched with
> Google, and didn't find any mention of this type of problem.

You can disable the ABS by pulling the right fuse.

I've heard of ABS problems being caused by a chafed wire to a wheel
sensor shroting out. But it's pretty rare.

When did you last have a brake fluid change? Maybe there's air in the
system?

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 >> Stay informed about: bmw e30 "crunchy" brakes 

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 >> Stay informed about: bmw e30 "crunchy" brakes 

In article <g0ap09$ame$1@jib.cs.utexas.edu>, dhs <dhs.TakeThisOut@cs.utexas.edu> wrote:
>In article <g09eo5$538$1@panix2.panix.com>,
>Scott Dorsey <kludge.TakeThisOut@panix.com> wrote:
>>It's possible the ABS is kicking in. Pull out the ABS relay and see if
>>the problem persists.
>
>OK, I yanked the ABS relay, and didn't see the problem see
>the problem in a 20min test drive.

Sounds like an ABS issue, then. Drive it around for a week or two like
that and see if the problem appears again. Intermittents are funy.

>>If it still happens, it's an ABS issue.
>I would have thought the opposite - that if the problem doesn't
>happen with the ABS effectively disconnected, that this points
>to an ABS problem?

Yes, I posted that before having my morning tea.

>If so, could this be the relay? The ABS light has been
>intermittently on in the last few months (and is, of course,
>on with the relay removed). The relay, unlike the controller,
>is cheap enough to buy new.

Wait.... wait... the ABS light has been intermittently coming on and
you did not associate it with your problem?

It could be the relay, but probably not. It could be an intermittent
wheel sensor or a wiring issue, too.

>Or maybe I have 3 bad controllers or ???

I don't know, and I don't know if your ABS system is new enough to
generate proper error codes for diagnosis. I do know that if you
continue to swap parts out without doing actual diagnosis, it will
cost you a fortune before you find the problem.

If you HAVE established that it's an ABS problem, you're probably
going to have to take it to an ABS guru. I don't drive any cars
new enough to have ABS so I don't work on the things much. I
generally don't like the whole idea of ABS but that's another story.

>If not, I'm not sure when I last changed the brake fluid, as
>another poster suggested - would that be a good place to start?

It probably has nothing to do with the issue, but you need to change
it out anyway to prevent other problems in the future. While you are
at it, do you remember when you last changed your transmission and
differential fluids? How about coolant? You gotta do this stuff.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."
 >> Stay informed about: bmw e30 "crunchy" brakes 

This message is not archived
 >> Stay informed about: bmw e30 "crunchy" brakes 

Bad form to follow-up your own posts, but I did want to note
that I ordered a new relay and will try that - the old
one had loose connectors that could cause signals that may
have confused the controller. But if that doesn't work,
are there computer diagnostics for ABS problems on an 89 325i?
The sensors are $150/per. Before I replace one, I'd like
to have some reason to believe that it's defective. A
quick visual inspection didn't show any damage.

Thanks,


In article <g0c8cs$fpc$1@jib.cs.utexas.edu>, dhs <dhs.TakeThisOut@cs.utexas.edu> wrote:
>In article <g0asui$sk3$1@panix2.panix.com>,
>Scott Dorsey <kludge.TakeThisOut@panix.com> wrote:
>>In article <g0ap09$ame$1@jib.cs.utexas.edu>, dhs <dhs.TakeThisOut@cs.utexas.edu> wrote:
>>>In article <g09eo5$538$1@panix2.panix.com>,
>>>Scott Dorsey <kludge.TakeThisOut@panix.com> wrote:
>>>OK, I yanked the ABS relay, and didn't see the problem see
>>>the problem in a 20min test drive.
>>Sounds like an ABS issue, then. Drive it around for a week or two like
>>that and see if the problem appears again. Intermittents are funy.
>OK - I'll try that, but the 20min drive was probably enough,
>since the problem usually appears now every 4-5 stops.
>
>
>>>If so, could this be the relay? The ABS light has been
>>>intermittently on in the last few months (and is, of course,
>>>on with the relay removed). The relay, unlike the controller,
>>>is cheap enough to buy new.
>>
>>Wait.... wait... the ABS light has been intermittently coming on and
>>you did not associate it with your problem?
>For the first 2 months that I saw this problem, the ABS light
>wasn't coming on - it's just been the last few months and it's
>not 100% correlated with the perceived brake problems.
>
>>It could be the relay, but probably not. It could be an intermittent
>>wheel sensor or a wiring issue, too.
>Any cost-effective way to check these? I have the Bentley manual
>and a meter.
>
>>>Or maybe I have 3 bad controllers or ???
>>I don't know, and I don't know if your ABS system is new enough to
>>generate proper error codes for diagnosis. I do know that if you
>>continue to swap parts out without doing actual diagnosis, it will
>>cost you a fortune before you find the problem.
>
>Eventually (see above). But the two controllers cost me $50 and
>about 10min to swap them in, and sometimes swapping parts is
>cheaper than taking it to even a competent mechanic.
>
>>If you HAVE established that it's an ABS problem, you're probably
>>going to have to take it to an ABS guru. I don't drive any cars
>>new enough to have ABS so I don't work on the things much. I
>>generally don't like the whole idea of ABS but that's another story.
>I don't either - this is the first car I've ever owned that had
>ABS, and it never kicked in until it started acting up.
>Figures.
>
>>>If not, I'm not sure when I last changed the brake fluid, as
>>>another poster suggested - would that be a good place to start?
>>It probably has nothing to do with the issue, but you need to change
>>it out anyway to prevent other problems in the future. While you are
>>at it, do you remember when you last changed your transmission and
>>differential fluids? How about coolant? You gotta do this stuff.
>I actually do - I just don't remember if the brake fluid was changed
>when we did the brakes earlier this year or last year. I change my
>oil every 3 months, and the other fluids at least every other year.
>
>I think your advice about an ABS guru is probably the best course
>of action, but finding one is another matter. One of my complaints
>about mechanics is that they all charge by the hour, regardless of
>whether they solve the problem or not. So its often cheaper to
>just swap-in lesser components (used ABS controllers, ABS relays, etc)
>yourself - even if you don't solve the problem, you still have
>probably saved money because the mechanic won't need to try those
>simple things.
>
>Any recommendations for ABS (BMW?) gurus in Austin TX?
>
>Thanks,
 >> Stay informed about: bmw e30 "crunchy" brakes