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

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On Sunday, November 2, 2014 8:11:31 AM UTC-5, N8N wrote:

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.
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On Sunday, November 2, 2014 9:07:35 AM UTC-5, trader_4 wrote:

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
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wrote:

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.
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On 11/2/14, 4:52 PM, snipped-for-privacy@snyder.on.ca wrote:

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.
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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.
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On 11/2/14, 10:13 PM, snipped-for-privacy@snyder.on.ca wrote:

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.
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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.
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On 11/2/14, 11:15 PM, snipped-for-privacy@snyder.on.ca wrote:

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?
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On 11/3/2014 12:36 AM, J Burns wrote:

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 .
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On Monday, November 3, 2014 12:36:55 AM UTC-5, J Burns wrote:

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The shop manual.
I know it's "common" to let 'em hang, but I don't like abusing hoses any mo re than I have to to get the job done.
I had a '71 Porsche 914 once, was working on it circa 1996ish. Probably st ill had the original hoses. When I replaced them I cut one open out of cur iosity, 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 p robably replace them and rebuild the hydraulics on principle. Just me...
nate
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wrote:

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.
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On 11/3/14, 7:07 PM, snipped-for-privacy@snyder.on.ca wrote:

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

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?
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