Brake pedal goes half-way to the floor, only the first time

[micky]

Brake pedal goes half-way to the floor, only the first time.



Finally driving my car again after it was laid up for 2 months.

I don't think it was like this 3 months ago.

When I first press the brake pedal, it goes half-way, but certainly not
all the way, to the floor, and at t hat point it stops the car very
well. If I press the pedal again within 2 or 3 minutes, it moves very
little before it's stopping the car.

If I wait maybe 15?? minutes, it's like the first sentence in the
previous paragraph.

What's the problem?

Bad master cylinder?

[Terry Coombs]

If you disconnected the caliper while you were working on the front end
the system probably needs bleeding - even if you didn't it probably does .
Some cars require bleeding both front and rear systems to maintain balance
in the valving system . Your repair manual should have the procedure .

--
Snag

[micky]

On Wed, 29 Oct 2014 09:48:47 -0500, "Terry Coombs" <snag...@msn.com>
wrote:

>micky wrote:
>> Brake pedal goes half-way to the floor, only the first time.
>>
>>
>>
>> Finally driving my car again after it was laid up for 2 months.
>>
>> I don't think it was like this 3 months ago.
>>
>> When I first press the brake pedal, it goes half-way, but certainly
>> not all the way, to the floor, and at t hat point it stops the car
>> very well. If I press the pedal again within 2 or 3 minutes, it
>> moves very little before it's stopping the car.
>>
>> If I wait maybe 15?? minutes, it's like the first sentence in the
>> previous paragraph.
>>
>> What's the problem?
>>
>> Bad master cylinder?
>
> If you disconnected the caliper while you were working on the front end
>the system probably needs bleeding

No, I didn't. (For others planning to do this: At first I did what I
usually do, I hung the caliper from other parts using a bent wire
hanger, but later I had a loop of fairly heavy stranded electrical wire
and that worked better.)

>- even if you didn't it probably does .
>Some cars require bleeding both front and rear systems to maintain balance
>in the valving system . Your repair manual should have the procedure .

Is the symptom I have really caused by needing bleeding? I had spongy
brakes once after doing something to the brakes, and every time I pushed
the pedal it was the same, spongy, like stepping on a sponge. Now
it's never spongy. When the pedal is going down the first time, there
is almost no resistance (only what comes from the spring) until there is
normal resistance.

[nestork]

I would check the brake fluid level in the master cylinder first. If
that seems to be OK, then I agree with Terry that bleeding any air out
of the brake lines and cylinders should correct the problem.




--
nestork

[philo]

Ditto and I'd do it ASAP!

[J Burns]

I'm foggy, but I think it could be a brake opening up mechanically, more
than normal, as you drive, gradually pushing fluid back into the master
cylinder.

If you have drums in the rear, one or both may need adjustment.
Sometimes pulling up the slack with the parking brake will act as a
temporary adjustment. If a rotor is warped, it could move the caliper
back and forth as you drive, gradually opening it.

[Tekkie®]

micky posted for all of us...

Is this the same car you did the suspension work on? If so you may have
introduced air into the system through cracks in the hose or bulging.
The first step is to top off the master cylinder then bleed the brakes
properly, per manufacturers instructions. If that doesn't work it is
probably the master cylinder, diagnose and repair per manufacturers
instructions. If it has power brakes it may be the booster but IDK your set
up. I have a faulty memory on this subject.

--
Tekkie

[larrymo...@my-deja.com]

I've had that happen with a couple of vehicles after I changed the
brake shoes or pads and didn't bleed their cylinders. Bleeding
always stopped the pedal from sinking.

After I bleed brakes, I close all the bleeder screws and pump the
pedal hard a few times. Then I open each screw, and usually no
fluid comes out right away, indicating there was still some air
inside.

[cl...@snyder.on.ca]

On Thu, 30 Oct 2014 01:25:39 -0700 (PDT), larrymo...@my-deja.com
wrote:

Badly adjusted brakes will have a low pedal on first push, and come
up and be firm on second. Poorly bled brakes will come up a bit on
each succuessive push but will never be "firm"

[Sasquatch Jones]

<larrymo...@my-deja.com> wrote in message news:3553ca0d-d20b-4cb3...@googlegroups.com...

If you bleed them, bleed the nearest one to the master cylinder first and then the next nearest, etc.

[trader_4]

Adjusted? I haven't owned a car with brake shoes in my lifetime. I
doubt Micky's import has shoes. And never seen a disc brake that you
could adjust.

[J Burns]

On 10/31/14, 8:25 AM, trader_4 wrote:
> Adjusted? I haven't owned a car with brake shoes in my lifetime. I
> doubt Micky's import has shoes. And never seen a disc brake that you
> could adjust.

Have four-wheel disks taken over? Well call me Rip Van Winkle! How do
you guys go parking without rolling into the lake?

The 1949 Chrysler Crown Imperial had four-wheel disks, but owners hated
them. The 1950 Crosley Hot Shot had them. Owners paid to have them
changed to drums.

The 1962 Studebaker Avanti established the standard of disks on the
front and drums on the rear.

If Micky has no drums, I believe brake mechanics could still be the
problem. Typically, runout is specified at less than .05mm.

If it's greater, and the cause is uneven transfer from the pads,
resulting in uneven disk thickness, the driver will feel pedal pulsing.

If that's not the case, and the measurement varies once per revolution,
the problem could be contamination between the disk and the hub face.

Otherwise, it could be a warped disk, which can happen putting lug nuts
on.

If a disk wiggles ever so slightly as the car runs down the road, the
caliper will wiggle. I can't speak from experience, but I imagine this
wiggling could open the caliper ever so slightly, causing a long push
the first time the brake pedal is pushed.

[cl...@snyder.on.ca]

On Fri, 31 Oct 2014 16:10:17 -0400, J Burns <bur...@nowhere.com>
wrote:

What kind of vehicle are we talking about? Was it ever stated?
Both of my cars still have drum rear brakes, with self adjusters which
by their very design have a tendancy to fail to adjust the brakes -
particularly on cars with automatic transmissions where the driver
seldom if ever uses the parking brake - which adjusts the brakes when
it is applied.

[J Burns]

On 10/31/14, 9:18 PM, cl...@snyder.on.ca wrote:
> What kind of vehicle are we talking about? Was it ever stated?
> Both of my cars still have drum rear brakes, with self adjusters which
> by their very design have a tendancy to fail to adjust the brakes -
> particularly on cars with automatic transmissions where the driver
> seldom if ever uses the parking brake - which adjusts the brakes when
> it is applied.

I wondered, too. Found it (September 30):
"I hit a curb with my car and broke in half the right half-axle, broke a
big chunk out of the RF rim and a piece the size of a tea-cup saucer
from the tire too, cracked my lower suspension arm, and severed the
right ball joint (2000 Toyota Solara, only has a lower ball joint. I'm
not sure how many cars this story covers. "

That car seems to have disks all around. After gazing into my crystal
ball, I'll vote for runout. It could come from damage to the disk or
hub, or it could be a little rust from all the time it sat disassembled.

http://www.motorsforum.com/tech/disc-brake-rotor-runout-46368-.htm

It may take thousands of miles of wear before the pedal starts to pulse.
Micky may have caught it quickly enough to fix it without buying
parts... if it's rust or dirt.

[trader_4]

On Friday, October 31, 2014 4:10:22 PM UTC-4, J Burns wrote:
> On 10/31/14, 8:25 AM, trader_4 wrote:
> > Adjusted? I haven't owned a car with brake shoes in my lifetime. I
> > doubt Micky's import has shoes. And never seen a disc brake that you
> > could adjust.
>
> Have four-wheel disks taken over? Well call me Rip Van Winkle! How do
> you guys go parking without rolling into the lake?
>

We're talking about Micky and the service brake, not parking brakes.

> The 1949 Chrysler Crown Imperial had four-wheel disks, but owners hated
> them. The 1950 Crosley Hot Shot had them. Owners paid to have them
> changed to drums.
>
> The 1962 Studebaker Avanti established the standard of disks on the
> front and drums on the rear.
>
> If Micky has no drums, I believe brake mechanics could still be the
> problem. Typically, runout is specified at less than .05mm.
>

Never said brake mechanics couldn't be the involved. The issue was that
Clare brought in "adjustment". Disc brakes don't have an adjustment.
And I'll bet Micky's brakes on that care are disc.

> If it's greater, and the cause is uneven transfer from the pads,
> resulting in uneven disk thickness, the driver will feel pedal pulsing.
>
> If that's not the case, and the measurement varies once per revolution,
> the problem could be contamination between the disk and the hub face.
>
> Otherwise, it could be a warped disk, which can happen putting lug nuts
> on.
>
> If a disk wiggles ever so slightly as the car runs down the road, the
> caliper will wiggle. I can't speak from experience, but I imagine this
> wiggling could open the caliper ever so slightly, causing a long push
> the first time the brake pedal is pushed.

I would agree that sounds possible. But it would seem it would have to
be quite a bit of wiggle to result in the pedal going half-way to the floor.

[cl...@snyder.on.ca]

On Sat, 01 Nov 2014 02:54:20 -0400, J Burns <bur...@nowhere.com>
wrote:

Well, runout on a disc WILL cause the problem if it pushes the
pistons back - effectively "backing off the adjustment"

[Geoff Welsh]

micky wrote:
> Brake pedal goes half-way to the floor, only the first time.

> ......

> What's the problem?
>
> Bad master cylinder?
>

that is indeed, the text-book symptom of a bad master cylinder.

GW

[J Burns]

I've been too optimistic. How could the hub transmit enough force to
break an axle, crack a suspension arm, and sever a ball joint, without
being damaged? Hub runout should show that a new hub and bearing is
needed. An optimist could hope the disk is OK.

[cl...@snyder.on.ca]

On Sat, 01 Nov 2014 11:04:59 -1000, Geoff Welsh <GeeD...@some.rr.com>
wrote:

Given the recent history of the vehicle -IE- it's damage history, I'd
be looking at the brake on the damaged axle first. Clamp off the brake
flex hose to that wheel. Is the pedal highand firm? If not, look
elsewhere. If so, you know where to look. Brake hose clamps are
available at Harbor frioeght and many auto parts/tool suppliers at
reasonable cost. Some are little screw clamps, others are a vice-grips
with round rod jaws. Make your own by brazing a 1/4 inch long 1/4 or
5/16" diameter steerl rods to a 6 or 8 inch cheap vice grips.

[N8N]

Supposedly these are one of the few things that Sears sells that are still worth it... apparently the same as S-K, Blue Point etc.

http://www.sears.com/craftsman-hose-pinch-pliers-set-of-3/p-00947218000P?sid=IDx01192011x000001&kpid=00947218000&kispla=00947218000P&kpid=00947218000&mktRedirect=y

Or, the plastic ones from Harbor Freight work fine.

Lots of guys just use flat jaw vice grips but I don't like doing that.

nate

[trader_4]

I'd like to see opinions from auto manufacturers one using these on
brake hoses. My concern would be that you run the risk of damaging the hose,
possibly resulting in later failure. And even if you did use them to pinch
the hoses, I would think they would cut off the fluid while you changed a
caliper. I tend to doubt they are going to hold pressure enough to test
the brakes with pedal pressure for functionality.

[N8N]

I actually agree with you; I have used them but would prefer to use a pedal jack to e.g. change a caliper. It's good to have them but I only use them when nothing else will do what I need it to do.

I don't know about the plastic ones but the metal ones should hold pressure in the situation the OP describes.

nate

[cl...@snyder.on.ca]

On Sun, 2 Nov 2014 06:40:48 -0800 (PST), N8N <n8n...@gmail.com>

I not only think they will, I KNOW they will. I've done it hundreds
of times. I've even used them to drive a car back to the shop after it
blew a fles hose (rear - body to axle) several times. (several
different vehicles) It was a very quick and accurate way to determine
where a low pedal problem came from. Block off the rear flex, pedal
comes up, rear brake problem, no use looking for the trouble in the
rear. Pedal doesn't come up? go to right front. Pedal doesn't come up?
go to left front. Still doesn't come up? look into the master.

[J Burns]

Trader 4 sounds right to me. I'd be scared to clamp a line made for
3,000 PSI.

I remember a car that came in smelling like burning brakes. I jacked up
the hot wheel and couldn't get the disk brake to release except by
loosening the bleeder. When I tried a stop on the road, the car pulled
to the other side, showing that the problem brake wasn't getting full
pressure. When I parked, I had to loosen the bleeder to release the brake.

It was as if something had kinked the line. I replaced it. Not long
afterward, the same thing happened to the other side.

I suppose normal braking pressure might be 1,000 PSI. It would take a
tight clamp to stop it. If I clamped it tight, I'd be afraid that down
the road I'd have a "kink" or a leak.

In view of the great damage from hitting the curb, the hub might have so
much runout that it might not require a gauge to detect it. Just a
ruler on a stable surface, held down by a weight, with the end pressed
against the hub. And some feeler gauges.

[cl...@snyder.on.ca]

On Sun, 02 Nov 2014 20:53:15 -0500, J Burns <bur...@nowhere.com>
wrote:

Your collapsed lined had nothing to do with clamping. Lines fail -
and the failure you mention is COMMON.. Clamping the lines WORKS, and
if done with the proper clamp it will not damage a good hose. Might
damage one that is already failing - which needs replacement
regardless.

[J Burns]

On 11/2/14, 10:13 PM, cl...@snyder.on.ca wrote:
> Your collapsed lined had nothing to do with clamping. Lines fail -
> and the failure you mention is COMMON.. Clamping the lines WORKS, and
> if done with the proper clamp it will not damage a good hose. Might
> damage one that is already failing - which needs replacement
> regardless.

I wish I understood what happened with that car. At first, I assumed
that the piston was jammed with dirt or corrosion.

If the line had collapsed, I would have expected pressure from the brake
pedal to open it so I'd get full braking on that wheel.

As I haven't seen it on any other vehicle, might those lines (just the
front) have been manufactured differently from most lines?

The other explanation is that something had been done to those lines
that isn't done to most lines. For example, I have read that if you
remove the caliper, you should be careful not to turn it 360 degrees (1
turn in the line) when you refasten it; a twist could cause the line to
burst later on.

[cl...@snyder.on.ca]

On Sun, 02 Nov 2014 22:55:46 -0500, J Burns <bur...@nowhere.com>
wrote:

Several things can happen. THe "lining" of the hose can separate from
the structural part of the hose and cause a "flap" that allows fluid
out to the caliper, but does not allow the caliper to return. In this
case, the brake initially drags, causing a pull to that side while
driving, and more on initial braking. When the brake heats up and
fades, the pull can move to the other side on braking. Can really
throw a beginner mechanic for a loop!!! Sometimes the problem is rust
in the metal crimp fittings expanding and squeezing the hose,
restricting fluid flow. This can have the same results, or it can just
cause the one brake to apply more slowly, causing a pull to the
opposite side on initial application.

The hose can also bulge, causing a soft pedal.
Then, of course, the hose can split/leak.

Other brake problems include calipers sticking due to corrosion or
fluid contamination, brake caliper sliders sticking, drum brake cyls
seizing, adjusters seizing or breaking, and caliprs or cyls leaking .

Leaking cyls can cause the brake to grab, or to loose friction.

Leaking grease seals can contaminate brake surfaces as well - causing
either a grab or loss of friction.

In other words, leaking cyls, calipers, or grease seals can cause a
pull in either direction.

Disabling brakes one wheel at a time can quickly isolate where the
problem is by elimination.

[J Burns]

Those two blocked lines are the only failures I remember. It was a
European car from the early 1970s. I may have found the cause:
corrosion at a fitting gradually squeezed the rubber lining together.
(Maybe the rear lines used a different kind of fitting.)
<http://ecomodder.com/forum/showthread.php/internal-flexible-brake-line-failure-finally-happened-me-21019.html>

Shop manuals always seem to say to hang a caliper by a wire so its
weight isn't on the line, but I've read that mechanics often let
calipers dangle on brake lines. Who's right?

[Stormin Mormon]

On 11/3/2014 12:36 AM, J Burns wrote:
>>
>> Disabling brakes one wheel at a time can quickly isolate where the
>> problem is by elimination.
>>
> Those two blocked lines are the only failures I remember. It was a
> European car from the early 1970s. I may have found the cause:
> corrosion at a fitting gradually squeezed the rubber lining together.
> (Maybe the rear lines used a different kind of fitting.)
> <http://ecomodder.com/forum/showthread.php/internal-flexible-brake-line-failure-finally-happened-me-21019.html>
>
>
> Shop manuals always seem to say to hang a caliper by a wire so its
> weight isn't on the line, but I've read that mechanics often let
> calipers dangle on brake lines. Who's right?

Manual is right, mechanics are wrong. That may
be common practice, but that doesn't make it
right.

-
.
Christopher A. Young
Learn about Jesus
www.lds.org
.

[cl...@snyder.on.ca]

On Mon, 03 Nov 2014 00:36:50 -0500, J Burns <bur...@nowhere.com>

Corrosion in the fittings is, as I noted, a major cause of the
problem.
Grease monkeys let calipers hang - real mechanics hang the caliper and
give the hoses some respect. They also use the right tool to clamp the
line to avoid dripping brake fluid everywhere when they remove the
caliper - and use the same clamp for trouble shooting.

[N8N]

The shop manual.

I know it's "common" to let 'em hang, but I don't like abusing hoses any more than I have to to get the job done.

I had a '71 Porsche 914 once, was working on it circa 1996ish. Probably still had the original hoses. When I replaced them I cut one open out of curiosity, the inside was swollen almost shut, so it may be normal for this to happen over years 'n' years of use.

Now my dad has a '73 chevy pickup that he still drives... I don't remember ever replacing the hoses on it... still drives fine, but were it mine I'd probably replace them and rebuild the hydraulics on principle. Just me...

nate

[J Burns]

On 11/3/14, 7:07 PM, cl...@snyder.on.ca wrote:
> Corrosion in the fittings is, as I noted, a major cause of the
> problem.

I see you did. Sometimes I don't comprehend what's in writing in front
of me!

> Grease monkeys let calipers hang - real mechanics hang the caliper and
> give the hoses some respect. They also use the right tool to clamp the
> line to avoid dripping brake fluid everywhere when they remove the
> caliper - and use the same clamp for trouble shooting.

If I see a clamp for sale, how can I tell if it's the right tool for
brake lines? The Lisle 22850 Hose Pincher looks like just the ticket,
but how do I know for sure?

[cl...@snyder.on.ca]

On Mon, 03 Nov 2014 19:37:50 -0500, J Burns <bur...@nowhere.com>
wrote:

The lisle unit is acceptable The SK 7600 series are better.
AMPRO T70547 Hose Pinch is another option. Halfords in Brittain also
sells a similar unit.
The KC 08205 BRAKE HOSE CLAMP is also a good looking unit.

Mine is like this irwin unit:

http://www.wahardware.com.au/specialty-pliers/11166-irwin-20r-plier-vice-grip-9-chain-clamp--0038548000299.html

I've had it for several decades (bought it in the early seventies)

[J Burns]

Amazon suggests the Lisle 22850 for brake lines, but Lisle's catalog
says fuel lines, vacuum lines, etc.

Amazon has 2 reviews for the AMPRO T7057. One said he used it to pinch
a coolant line. It failed to seal, and he ended up with coolant running
down his sleeve.

The other liked it. He used it to pinch a brake line when he changed
calipers, and it didn't damage the line, as happened every time he used
Vise Grips. There's a guy who's not afraid to damage brake lines, again
and again! (I believe if you put plastic food wrap over the top of a
brake-fluid reservoir and screw the cap on, that will keep it from
draining through an open line.)

The Irwin pinch-off tool is a Vise Grip 7" RR. It weighs 13 ounces.
Irwin says it's for tubing and opens to 1/4".

I use 6" long-nose Vise Grips to work on gravity-fed gas lines. At the
tip, the jaws are parallel when they come together and nearly parallel
when 1/4" apart. It weighs only 6 ounces. I've seen no damage. With
gravity-fed gas line, there's not much at stake.

[Oren]

On Sat, 01 Nov 2014 11:04:59 -1000, Geoff Welsh <GeeD...@some.rr.com>
wrote:

You ruled out a leaking wheel brake cylinder, leaking caliper, brake
line or connections?
--
"Trust me, I'm from the government. I'm here to help."