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ABS Brake Questions and Answers - This category contains featured questions
as examples. They relate to most vehicles.
Question: 2002
Ford Windstar 3.0L mileage: 156,000.
Can you tell me what the max wear specs
are for my front rotors?
I had a mechanic tell me he would have to
turn the rotors down first ($30.00) before
he would know if I needed new ones or not.
Needless to say...I walked out.
Answer: With the proper
measuring equipment any reputable mechanic
should be able to measure the rotors and tell
you if they can be machined within
specifications.
The minimum thickness for the rotors
should be permanently marked on the rotor
itself.
Question: 1999 Pontiac Grand Prix mileage: 109,000. Recently
replaced the rear disk brake calipers, rotors & pads and bled the complete
system. Brake pedal is pretty firm w/o engine running. However, when
the engine is running you have to press the brake pedal at least halfway to get
any braking action & nearly to the floor before it stops. It doesn't
feel firm in my opinion. What I fear may have happened is the master
cylinder may have completely drained. When I was replacing the first
caliper I let the brake line dangle in a container to collect the dripping
fluid. Quite a bit of fluid (probably a pint) had drained out by the time
I was ready to connect the brake line back up. I left the brake line
connected to the old caliper while I changed the other side. When I was
ready to bleed everything, I opened the bleeder fitting & let gravity fill the
line & caliper. Did this on both sides before using the typical two-person
method to get the rest of the air out of the lines. When I was not
satisfied with the results after bleeding the rear calipers, I bled the front
calipers, too. What have I missed? One last bit of
information, the rear calipers on this vehicle have an
integrated emergency brake.
Is there any adjustment required to this
mechanism that may cause this condition?
None of my manuals indicate it, but I was
told they may need to be 'ratcheted up' by
working the emergency brake levers on the
calipers.
I tried activating the emergency brake countless
times w/o getting a change in the pedal while
the engine is running.
Answer:
There is a possibility that you still
have some air in the brake system.
Also, check the rear emergency brake
ratchet in the calipers.
Although they are supposed to be
activated by pressing the parking brake pedal,
we have found these ratchets have a tendency to
hang-up and not adjust, as they should.
Question:
1999 Chevy Silverado mileage: 112,000.
My question is: I changed the motor in
the truck, it used to have a diesel (6.2) so I
had to change the master cylinder and booster
but now I have good brake pedal when the truck
is not running, once you start the motor I have
no pedal at all.
I have bled the system several times but
nothing changes.
What should I try next?
Answer:
To find your problem, you will have to
isolate the different components of the system.
Remove the two brake lines from the
master cylinder and insert two suitable plugs in
their place.
Start the truck and try the brake pedal.
If you now have excellent brake pedal,
the problem is obviously in the brakes on the
wheels.
Remove one of the plugs and re-attach one of the
lines.
This should help you pinpoint the source
of your problem.
If the pedal now goes to the floor, you
know which one is bad.
Follow this procedure to the other brake
line.
Question:
1989 Chevy 1500 4.3 mileage: 130,000.
Periodically the dash brake like flashes
a code and will not go away until I disconnect
the connectors to the brake module next to the
fluid reservoir.
The code is 8 short flashes followed by
one longer flash.
This continues until I disconnect the
cables.
The brake fluid levels appear fine.
The pads and shoes look fine.
I don't see any leaks in the system.
I have not been able to tie the start of
the flashing to any specific incident such as
hitting the brakes hard.
Any hints?
I assume the flashing code means
something.
The truck brakes fine.
Thanks
Answer:
The code you read on the brake light
would indicate a faulty brake dump valve.
Question:
1995 Chevy blazer 4.3 mileage: 85,000.
Anti-lock brake light comes on and stays
on after vehicle reaches over the speed of 8
miles an hour.
Have checked connections, speed sensor,
resistance, all checks out all ok, no set
computer codes, any suggestions?
Answer:
Recheck for codes on the ABS computer.
If the anti-lock light comes on, it is
storing codes.
Question:
1992 Buick Skylark Quad 4 2.8 liter mileage:
98,000.
The anti-lock brakes seem to engage right as the
car nears a stop.
There is a sound as if a valve is
applying and releasing pressure and at this time
the brakes grab then release at there own will.
I have been told by a dealer that there
are three parts to this anti-lock system and all
have been tested and were fine.
He said the rotors were warped, turned
them and the car worked fine for about 1000
miles and then started again.
Placed new rotors on this time but the
problem still exists.
It does not happen all the time but
enough to always make you wonder.
Other mechanics have said the whole
anti-lock unit needs to be replaced.
Brakes work fine at braking at high
speeds, it only occurs nearing a stop but its
making the car feel unsafe to drive.
Any advice would be very helpful and
thank-you for your time.
Answer:
It sounds like a thorough job has been done
checking out the front brakes.
Your problems are most likely caused by
loose or weak return springs or a faulty parking
brake mechanism in the rear brakes.
Question:
1990 Ramcharger 2 wheel drive 360 mileage:
280,000.
BOB or KEN - I have only front brakes and
have determined that it is a problem with the RWAL system - the antilock light in the dash
stays on - I have replaced the speed sensor and
the speed sensor wire harness from the speed
sensor to the first junction and still the
problem persists: - I have checked the condition
of all the brakes and they are fine
Answer:
The anti-lock brake valve probably is
causing the problems you described.
Replacing it should fix your problem.
Question:
1990 Mercury Cougar 3.9L mileage: 88,000.
I have recently been experiencing the
following braking issues (this is a non-ABS
system):
At first when I applied the brakes, it appeared
that too much brake was being applied.
It has now been progressively getting
worse.
Now when I apply the brake (even lightly) and
let off, the car continues to apply the brakes
to the point were it sometimes wants to stop the
car.
After reading about my system, I suspect
the booster.
Does it sound like I am in the right area
or should I suspect the check valve first?
Answer: Several things to check; the power brake booster, the rear
brakes, and the rear brake return springs.
Question:
94 Ford F350 7.3 diesel mileage: 62,000.
My brake pedal slowly bleeds down as in a
defective master cylinder, but we changed that
twice.
The rear brakes have been adjusted, the system
bled and we have 20+ inches of vacuum at idle.
(A Ford mechanic told me that
insufficient vacuum can cause this.
He also told me that as far as he knows,
a defective ABS unit can’t be the cause).
What is the cause?
It does not bleed-down with the engine
off (no vacuum).
Answer:
You have either another bad master
cylinder or a leak somewhere in the hydraulic
brake system.
Question:
1988 Chevrolet 1500 Pick up 5.7 TBI mileage:
170,000.
My question concerns anti-lock brakes.
I just recently purchased my truck and
from the beginning, the breaks have never felt
right.
Sort of firm at first then steadily travel down
past the gas pedal.
I inspected them the other day and
discovered that the front pads were worn
unevenly.
The inside pads (right left) were worn down to
the rivets, while the outer pads could have gone
another 10000 miles or so.
The backs however were hardly worn at
all.
I know that the fronts wear out about twice as
often as the backs do but they hardly looked
worn at all.
I noticed no fluid leaking from any of
the wheel cylinders so I replaced the front
pads, cleaned, and adjusted the rear.
The front calipers did not seem stuck
(suspected in the uneven pad were).
I then bled the breaks at all four wheels
and noticed no air bubbles from any of the
cylinders.
I have never owned a vehicle with rear
wheel antilock breaks and I was unsure exactly
what they should feel like.
The truck will stop but not like, I am
accustomed to (pedal feel).
You know!
Question 1:
When bleeding power breaks does it make a
difference if the engine is running or not?
Question 2:
Could I have a problem with the dump
valve that is mounted under the master cylinder,
relieving the rear break pressure prematurely?
Question 3: Does the ABS system look at
the same vehicle speed sensor that the cruse
control looks at?
I ask this because the cruse control does
not work either.
Question 4: If the speed sensor was
faulty the computer would think that the rear
breaks were locked up thus relieving the
pressure through the dump valve.
Is this a possible cause?
Thanks for any thoughts on this
matter....
Answer:
After reading your question, two things
come to mind that may be causing your problems.
The front caliper not sliding properly is most
likely causing the uneven brake pad wear.
Cleaning up the slides should fix that
problem.
A faulty master cylinder is probably causing
your other problem.
Replacing it should do the trick.
It makes no difference if the engine is
running or not to bleed the brakes.
Question:
1997 ford Explorer V6 mileage: 69,000.
Have turned rotors, replaced brake pads.
When you press the brakes to stop the
pedal surges back and forth towards you and
makes the car jerk.
Answer:
From what you described, it sounds like
your brake rotors were turned improperly.
Check to see that they run true.
Question:
1992 Mercury Cougar 5.0 mileage: 95,000.
The metal brake line from the right front
wheel to the master cylinder has a small pinhole
near the right fender wall down low.
Replacing the whole line would be very
difficult due to running behind the engine and
having many curves and bends.
What would be the best way to repair the
line?
I have been told I can use what was described as
a "double flare kit".
Cutting out the bad area and connecting a
new section with fittings.
In addition, can brass fitting be used or
only steel fittings.
I do not have ABS.
Answer: The preferred way to repair
your problem is to replace the entire steel
brake line.
It can be done as you suggest by splicing
in a new piece of tubing.
Be aware when doing the repairs on steel
tubing with a double flair, it can be very
difficult to do it properly.
Brass fittings are okay.
Do not under any circumstances use
copper tubing for the repairs.
Question:
1975 Toyota Land Cruiser FJ 40 2f mileage:
101,000.
Well, simply put, my brakes do not work.
I have replaced all the pads but nothing
works, when I step on the pedal there is no
pressure at all but when I pump them they seem
to work fine, but once there pumped up all the
way if you hit them again the pedal will go to
the floor, with no pressure at all.
There is plenty of fluid, and there is
not a drop of fluid leaking anywhere, not at the
wheel cylinders or the brake booster or at the
master cylinder.
Oh yeah, they are drum brakes front and
back!
Answer:
Two things to check. Are the brakes
adjusted properly? Is there air in the
hydraulic brake fluid system.
Question:
1989 Honda Civic DX 4 cyl mileage: 130,000.
I've been having trouble with my brake
system.
Had front and rear pads and rotors replaced
8/99, but the brakes still did not feel quite
right.
Had the booster and master cylinder
replaced last Monday, and the new booster went
out on Thursday.
My brakes locked up and started smoking,
fried the front brakes altogether.
Do I need to try another mechanic?
How common is it to get a faulty booster?
Answer: We are sorry to hear you are
getting the run-a-round with your car repairs.
Talk with friends and neighbors to locate a
professional auto mechanic you can trust.
Have him/her inspect the car giving
him/her the same information you gave us.
Faulty power brake boosters are not
common but it is possible to get one.
Question: 94
Pontiac Sunbird 2.0 mileage: 172,000.
Brake pedal goes slowly to the floor when
coming to a slow stop; you can hear the ABS
brakes clicking on the master cylinder.
Is it brake sensors or master cylinder
ABS?
Answer:
It is master cylinder ABS.
Question:
95 Ford/Explorer 6 Cyl mileage: 68,000.
My Explorer has been diagnosed with
faulty ABS sensors in the front.
I am unfamiliar with repairing ABS
brakes, but would like to do the job myself.
Can you tell me the steps, or am I
getting into trouble?
Answer:
Replacing the ABS sensors is relatively
easy.
If you have done other brake jobs, it is
straightforward.
Unplug the sensor wires and unbolt the
sensors.
Repair Topics /
Brake Pads-1 /
Brake Pads-2 /
Brake Pads-3 /
Brake Pads-4 /
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Brake Pads-8
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