Brake bleeding techniques

I have a 92 grand voyager and a 94 grand caravan. I have a couple
brake bleeding questions.

First, the manual says I can use the old procedure for the 92, but
need some sort of electronic abs tool for the 94 and should take it in
to be serviced. Personally, I'd rather eat glass. So is there a way
for me to bleed the lines on the 94 without the tool, or
alternatively, is this tool inexpensive?

Second, i'd like to bleed the lines on the 92 with the tool that
attaches to the top of the master cylinder and pressurizes it. Is
this tool ok for this abs system?

thanks

brian

 

Let's assume that your '92 GV is a standard, non-ABS-equipped vehicle, and
that your '94 GC has the optional ABS equipment.

Your '92 brake fluid can be safely and easily changed via the "regular"
manual bleeding method (see various shop manuals and online web sites for
this procedure). You can use the master cylinder pressure bleeder you
mention, but there's no added benefit to doing so if all four wheel
cylinders and the master cylinder are manually bled correctly. And, of
course, there's the expense involved in buying such equipment, not to
mention the time involved in learning how to use it properly.

Your '94 with ABS is different. Yes, you can manually bleed this vehicle's
brake system. However, this does not change the fluid inside the ABS pump
and related piping circuitry. That fluid can be purged only by use of the
proper procedure using an OBD III scan tool.

Here's how a properly trained and equipped professional Mopar or independent
service facility does the job, and why it costs 2-3 times what a "normal"
brake fluid change costs: First, the brake system is bled the "standard" way
(manually, or using a pressure bleeder -- it doesn't make any difference,
except in time and the number of mechanics needed). Then, the OBD III tool
is used to cycle the ABS pump until the fluid runs clear. Then a final check
at all four wheel cylinders.

Some "experts" will tell you that you can manually bleed an ABS-equipped
system, then go out and brake like the devil to activate the ABS system and
flush the ABS pump and circuitry, then do another manual bleed. This may or
may not work satisfactorily, but it does raise questions about how many
stops are required, and probably involves what may or may not be unsafe
driving actions depending on traffic, road conditions, etc.

I manually bleed my non-ABS vehicles, with an assistant behind the wheel to
push down the brake pedal. I spend the money to have a Chrysler dealership
bleed my ABS-equipped vehicles.

What happens to ABS systems that aren't bled properly? After about 4-6 years
(depending on climate, etc.) crud begins to collect in the ABS circuitry.
Sometime after that the ABS pump/circuitry gets so corroded and/or gunked up
it fails, which causes a very expensive replacement of the main ABS parts
($600-700 and up, depending on manufacturer, age of system, etc.). I've seen
it happen on cars/trucks as "old" as 5-6 years which were driven mostly in
city traffic in humid coastal climates. Vigorously-driven ABS vehicles seem
to fair a bit better, which is no doubt due to the fact the ABS is activated
often enough to flush fluid out of the ABS passages.

These are my observations and opinions. Yours and those of others might
vary.

 

You'd rather eat glass than have brakes that work properly and last a
long time? Interesting philosophy.

I don't think scan tools are all that expensive, probably a couple
hundred or so.


Matt

 

Well first of all it's a DRB scantool that is used for this, not OBD -III
unless he's talking about a brand name of a tool.

Secondly, the cheap (ie: cheap meaning under $500 used) scantools
do not have the functionality for bleeding ABS. You must purchase either
a new or used genuine Chrysler DRB scan tool (such come up on Ebay from
time to time and always sell for at leat $2K or so) or I believe the
high-end
scan tool from OTC (genisys) can do it, also OTC makes a tool called
the "OTC Air Bag/ABS Scan Tool" that can do it.

Ted

 

In the interest of clarity, thanks for mentioning the DRB Scan Tool or DRB
Diagnostics Tester, which are two terms Chrysler uses to describe the
diagnostic readout box (DRB) or scan tool that connects to the On Board
Diagnostics (OBD) port connector usually to the left or right of the
steering column at the bottom of the dash in recent-vintage Chrysler
vehicles. But let's not get led astray by confusion over terms.

I just revisited page 5-92 of my '97 T&C, Voyager and Caravan Service
Manual. It says to first bleed the standard or base brake system (using
either the manual or pressure method), then to use the DRB scan tool
connected to the OBD port to "initiate the 'Bleed ABS' cycle one time." This
is done after the brake pedal is applied firmly; the pedal is released after
the ABS bleed cycle is completed.

Then the shop manual says to bleed the base brake system again, then repeat
the "Bleed ABS" cycle, and to keep doing this "until brake fluid flows clear
and is free of any air bubbles." This is to be followed by a test drive to
confirm proper brake system operation and that the brake pedal is firm.

As implied in my original response, this is why an ABS system bleed
procedure is more expensive than a standard brake system bleed (time +
expensive equipment = money).

Other Chrysler shop manuals I have agree with this procedure for bleeding
ABS-equipped systems.

The point is that it is necessary to bleed the standard/base and ABS systems
separately. To do so correctly requires the proper scan tool (or whatever
it's called by Chrysler or the manufacturer of the tool) to activate the ABS
Hydraulic Control Unit (HCU) pump through the OBD port or connector.

Yes, the DRB Scan Tool used by Chrysler dealers is a very expensive tool.
It's actually a sophisticated computer that's programmed to do a wide range
of specific diagnostics and service procedures for a wide range of Chrysler
vehicles.

I am leery of any relatively inexpensive ($200-$400) store-bought scan tool
that promises to replicate the multi-thousand-dollar Chrysler DRB Scan Tool
functions. This is why I urge anyone with an ABS-equipped Chrysler product
to get the brake fluid bled regularly by a Chrysler trained and equipped
dealership. Every 3 years or so should be a sufficient brake fluid
bleed/change interval in most climates. My local dealer charges about $30
for a standard bleed, and about $80 for an ABS bleed.

On the same page 5-92 of my '97 Chrysler minivan Service Manual, it also
says, "Under most circumstances that would require brake bleeding, only the
base brake system needs to be bled." Assuming that a ABS-equipped vehicle
owner has the base brake system bled every 3 years or so, this probably is
good advice. However, in my experience very few vehicle owners have anything
done to their brakes until something fails or wears out. Most car drivers
have no idea they should change brake fluid regularly.

I've bought dozens of vehicles that are 2-10 years old (usually from the
original owner), and all but a few have still had the original brake fluid.
I always ask if the brake fluid has been changed, and the response usually
has been, "I'm not sure" or "I don't think so." Upon bleeding the brakes,
the dark color of the fluid and the bits of corrosion have confirmed they
had never changed the fluid.

Since the base brake system and the ABS system both use the same brake
fluid, and that fluid gets cycled through the ABS circuits occasionally,
then it stands to reason that if the base system bleeding unveils
contaminated fluid, then the ABS system also has contaminated fluid. This is
why I contend that both systems should be bled, notwithstanding the Chrysler
Service Manual quote above.

 

I was kidding. I've had a lot of experience with bad mechanics, which
is what led me to start doing my own car repairs years ago. There's
obviously a lot i cant/wont do. I'd hate for brake bleeding to fall
into that caregory.

As a tangent, this same shop manual says that removing old races from
a hub is beyond the normal home mechanic and should be done by a shop.
Makes me wonder about that advice elsewhere in the manual.

brian

 

I started doing my own work back in the mid-'60s when Chevy mechanics
couldn't do routine maintenance work on my Corvair Corsa without making it
run worse or become unsafe. In one case, they even sabotaged my car after a
warranty repair by only finger-tightening lug nuts!

You and I and anyone else who wants to can still bleed brakes at home with
simple tools. But I'm not going to spend thousands of dollars to buy a tool
to properly flush the ABS portion of my brakes. And I'm not going to ignore
the ABS system. It's a lot cheaper and gives me peace of mind to rent
Chrysler mechanics and their high-faluting equipment to do it right.

I also change my own bearing races with nothing more than simple hand tools.
All you need is a brass punch, a heavy hammer and some blocks of wood. Once
the old race is out, I use it to help drive the new one into place. Just did
that last summer on Mitsu Mighty Max front hubs, in fact.

Experience is a great teacher, and I've learned how to do most car repair
jobs myself. I buy model year-specific factory shop manuals, read them and
learn what it takes to do a job right. There are many satisfactory
work-arounds. But there are some things that require equipment I don't have,
such as a spin balancer or alignment machine or brake disc/drum lathe or DRB
scan tool. That's when I let the pros do it. At least I know what they are
supposed to do and can quality-check their work.

But most people have neither the inclination, nor the talent, nor the desire
to learn how to do even simple auto maintenance. And they don't do anything
about it, even when they know they can save big bucks doing routine
maintenance and repairs. No wonder the average car owner's at the mercy of
the auto repair industry.

 

It's not thousands of dollars. The OTC tool I mentioned earlier that is
specifically
for bleeding ABS retails at about $900 and used ones can be had for in the
$500
range (although those may not have all updates and thus may not be able to
do every
current model vehicle on the road)

But how do you really know that they are doing it right unless your standing
over
them?

I can still remember when I did my first brake job on my own car, years ago.
I had been doing my own minor work for a few years and finally decided to
attempt brakes. I read all I could about it and used the FSM of course -
and
in the process discovered 2 things - first that there are a number of
operations
in doing brake work that have quite obvious shortcuts - cuts that might seem
to
be OK but could compromise long term reliability. Such as reusing brake
shoe return springs. Second I discovered that to really do them right
requires
a fair bit of time, espically if you find hydraulic leaks that need
attention.

I therefore have come to the conclusion - fair or not - that probably 70% of
brake
jobs that are done are done too fast, skipping steps, and in short aren't
done
right. This is keeping in mind that every corner tire shop in the country
advertises
that they do brake jobs. I would hope that the vast majority of brake jobs
that
are done at real mechanic's shops by contrast are done properly - but to be
honest
after doing my own brake jobs now for years, I just cannot trust anyone else
to do them.

So, is it perhaps a bit of a stunner to discover you have to drop $500 on a
tool
to do your own ABS brake system right. But folks, that's the future of auto
repair. You may be able to argue that it's cheaper to hire a mechanic to do
the
job, but if that mechanic makes a mistake because he's rushing because his
boss
is pushing him because they booked in too many repair jobs that week, then
suddennly that $500 tool doesen't seem that expensive anymore.

I do concur on tires - I don't have the space in my garage for a tire
mounting
machine, or spin balancer even if someone gave them to me for free. But why
are you even bothing to turn brake drums or discs? For the money you save
on a brake job, just throw the used drums or discs out and buy new ones.
And
while a DRB tool is nice to have, even today with the computers in engines,
the vast majority of failures are still mechanical, and most DIYers can
easily get
by with one of those new $150 scan tools that plugs into the diagnostic port
and
you use a computer to download the info from it.

Where I see the real need for professional repair today is in auto bodywork.
Frame alignment is not something you can do in your garage.

That is I think a really narrow view of things, it's a middle class
viewpoint I think.

Time was that only the rich bought cars and used them for 5-6 years then
sold
them at 6,000 miles. Everyone else, middle class and on down, when they
bought
a car they drove it until the wheels fell off. Thus a lot more people
were stuck trying to keep 15-20 year old vehicles running, thus they had
much
more interest in learning how and in doing simple auto maintainence.

Then the auto industry realized they could sell more cars if they convinced
the
middle class to give up owning a car older then 10 years old, and you ended
up
with the situation you have today, where the middle class are the new car
purchasers
and never really own a car, they are making car payments the rest of their
lives.
The lower middle class and the poor people who years ago used to take the
bus
are now able to afford the used vehicles that the middle class is
discarding, these
are the ones who cannot afford to pay people to work on their cars, and they
all seem to be working on their own cars. And the eco-greenies are running
around
wondering why nobody is riding the fancy bus systems they are getting the
city governments to build for them.

Ted

 

That's getting to where I could buy one.

I'm on a quest to do everything myself when it's practical. It seems
as though it's impossible to find anyone these days, regardless of the
profession, who cares about the work they're doing. It's like you
need a lawyer following you around to make people do their jobs.

I try to do this. Some shops don't care. Others get real upset with
me in a hurry. Makes me wonder what they're up to. Most claim that
their insurance company won't let customers in the shop, which is
probably true (i hate insurance companies also) but sure feels like
bull shit. I guess if I had a shop, I would have that attitude also.
I know enough not to fall into a pit or slip on oil, but most people
probably don't.

It took me a week's worth of evenings to get it done. That was with
multiple trips to the auto parts store though.

This is how I feel about it. I had a suburban that was making a lot
of valve train noise at 80k miles. I took it to the dealer. My first
mistake was not leaving when one of the mechanics tried to tell me
that it's perfectly ok to put water in the oil filler. I'm not making
this up. Then another mechanic told me that I needed new lifters.
$1300. I then asked if I was going to lose the bottom end in a couple
weeks wondering weather the work was worth it. They assured me it
would be ok. The engine was indeed quieter when I got it back, but it
left me stranded three weeks later with two bad connecting rod
bearings, on a sunday night, in the snow, with four kids, in the
middle of nowhere, with a 3000lb trailer. When the customer has
better insight into what's wrong with the engine than the professional
mechanic, that's a problem. Had they pulled the oil pan, they
probably would have found metal.

Can you even be sure that the mechanic bled the abs portion of the
system? The customer would probably never know unless there was air
in the line. A tool doesn't do much good if you don't use it.

They're on my long term shopping list. I have four cars and five
little kids. (I may need a parking lot soon) Also, I think I would
balance more often if I had the machine. I also want to be able to
patch nails from the inside rather than use the plugs. The lift comes
first though.

That's my attitude now. I didn't replace the disks this time because
they were nearly perfect. I did replace the drums though. This
really is only practical on cars where millions were sold. A set of
back rotors for a vw passat ran $250 a pair.

I'm seriously considering opening a body shop. I think this is
another area where simply doing acceptable work would make you one of
the best in the industry.

I've vowed never to do this again. It's my mission in life not to be
a mindless consumer. I also resent the idea of spending $30,000 for a
car that's worthless before all the payments are made. Big rigs go
300,000 to 1,000,000 miles without a rebuild. Car manufacturers could
easily do the same but won't because they'd kill their long term
sales.

brian

 

I've seen a number of diesel powered cars that lasted 300,000 miles.
I've seen very few big rigs that go more than 500,000 without major
overhaul of the engine at least, and often the transmission and axles as
well.

Cars could be made to last longer, but you'd pay a lot more than you do
today. I'm guessing most people wouldn't pay as many people only want a
given car for 3 years or so anyway as they always want the new model.
I'm like you, I like to maintain my own cars and try to make them last a
long time (my current daily driver has 145,000 and climbing), but we're
actually a small minority of car owners.

Unfortunately, as you are finding with your ABS brakes, modern cars are
getting harder for the average backyard mechanic to maintain. I still
do most of my own maintenance, but I take my vehicles to the dealer for
things like transmission oil changes (I don't have flushing equipment),
ABS brake work, etc. Fortunately, I have a local dealer that I trust
and whose mechanics have thus far proved pretty competent in most
things. They aren't as sharp at electrical troubleshooting as I'd like,
but then I'm an EE and can do much of that myself.


Matt