Bleeding Brakes

[TheBigDog]

It should not be this much of a challenge. In fact it should be pretty damn simple. Changed front calipers. Bled brakes. Complete brake failure. Now I am driving a rental car and trying to decide what my breaking point is for having a professional look into this. WTH!

Why is is that nobody has developed a closed loop system for hydrolic brakes that would be self bleeding? WHY!!

Bill

[Moontanman]

Describe what you call brake failure..... no pedal, soft pedal, no stop at all or just not enough stop? Possibly you need to bleed your brakes more, you didn't get fluid on the disc did you? brakes are not exactly my forte' exactly but I have done a few of them in my time....

[lawcat]

Bleeding brakes is no funny matter. Read this and decide that maybe professional help is required:
http://auto.howstuffworks.com/auto-p...-bleeding3.htm

The site links to these pertinent sites.
http://www.popularmechanics.com/auto...o/4213448.html
http://www.drivewerks.com/tech/mult_bleed_brakes2.htm

[TheBigDog]

Originally Posted by Moontanman

Describe what you call brake failure..... no pedal, soft pedal, no stop at all or just not enough stop? Possibly you need to bleed your brakes more, you didn't get fluid on the disc did you? brakes are not exactly my forte' exactly but I have done a few of them in my time....

Brake to floor, no stopping, no slowing, no nothing. In fact there was a sensation of acceleration. Pumping did not help. I bled them again and they improved enough that pumping them had an effect, not I did not see any air come out when I did this. The next step is to bleed them from all four wheels again, and let enough fluid pass through to know that any air in the lines has been exhausted out.

But I am done with it for a day. The rental is until Monday, so I am going to worry about it then. Just set off fireworks, now to go have some.

Bill

[Cedars]

Originally Posted by TheBigDog

Brake to floor, no stopping, no slowing, no nothing. In fact there was a sensation of acceleration. Pumping did not help. I bled them again and they improved enough that pumping them had an effect, not I did not see any air come out when I did this. The next step is to bleed them from all four wheels again, and let enough fluid pass through to know that any air in the lines has been exhausted out.

But I am done with it for a day. The rental is until Monday, so I am going to worry about it then. Just set off fireworks, now to go have some.

Bill

Make sure the fittings sealed. Did you bleed the anti-locks too? Did you have someone helping you (pushing on the brake until the flow was good)? Was the car on jacks when you were bleeding the line? Sometimes the bubbles work out while they sit. Could there be a pinhole in the lines? I blew my front brakeline stopping for a baby turkey last fall and it was soo rusted it blew. 80% of the time, when we do a caliper, we do the line at the same time if theres a hint of weakness (depending on the hassle involved).

[arkain101]

"You should find out the suggested bleeding order. Most vehicles suggest a specific order in which you are intended to bleed the brakes to ensure that air is efficiently evacuated from the system. In the absence of this information, you should bleed the back brakes first, and you should start on the driver's side; So for a USDM vehicle, you should bleed the rear left first, followed by the rear right, then the front left, and finally the front right."

"The person in the car should push in the brake pedal and hold it down; Now you close the valve. If the pumper raises the pedal before you close the valve, some air will be drawn back into the system (or, if you're lucky, some of the fluid in your line) and possibly compromise your bleeding job. The tighter your clear line fits onto your bleeder fitting, the less likely this is to happen.

Use a hose that leads vertically from the nipple bleeder to not only acquire a safe amount of back flow, but also to witness the extent of the air that is being pumped out of the system.

The pumper can pump the brakes a couple times, and then with them up, you open it again. Repeat as necessary until the fluid comes out completely free of bubbles. The purpose of pumping the pedal with the bleeder closed is to unify the air bubbles in the system to aid in pumping them out. It sounds superstitious, but it makes a significant difference."

Tricks and Tips

Sometimes air bubbles can get trapped in vertical bends in the brake line. That is, if the brake line has an up and down pathway towards the caliper air may refuse to pass through these areas. This is why when I start my bleeding process (especially when there is no pedal pressure) I try to do it very quickly. Slamming the pedal down forces fluid through the lines and can get the air bubbles to move, since they tend to climb back to the highest point in the line, you then have to close the bleeder and have the person on the pedal immidiately try to push the pedal down again... Do this quickly a number of times untill you notice a large amount of air leave the system, or when you feel it has been pumped enough times. Infact, during this proceedure all you need to do is keep your finger firmly pressed on the end of the bleeding hose.. (or install some kind of one way valve that accomplishes the same effect) WHen the peddle pusher pushes down your finger will be unable to stop the fluid/air form leaving the hose, however, when the pedal comes back up, your finger will seal the flow of the hose and nothing will backflow. This way, the pedal pusher only needs to rapidly pump the pedal while you hold your finger on the end of the line (aiming a spray into a container of some sort)

This is where tools that push a constant flow through the system come in handy, since they are much less likely to break up air bubbles.

After this somewhat violent method, you can then slow it down and work out smaller bubbles more carefully, using the open/close up/down proceedure.

Always look for air bubbles in the resivoir before starting!!! It will do you no good to pump bubbles into the line. If you have bubbles in the resivoir you may have to slow down the pedal pumping, and wait for for the fluid to desaturate the air aswell.

[arkain101]

Originally Posted by TheBigDog

It should not be this much of a challenge. In fact it should be pretty damn simple. Changed front calipers. Bled brakes. Complete brake failure. Now I am driving a rental car and trying to decide what my breaking point is for having a professional look into this. WTH!

Why is is that nobody has developed a closed loop system for hydrolic brakes that would be self bleeding? WHY!!

Bill

imo, you may also want to manually fill the calipers before starting the bleeding process. A low fluid level can cause more bubbles to form.

It is a rather easy process, but sometimes you have to begin by moving the fluid in a quick and almost constant flow to get past some annoying bends / and deal with large bubbles.

[arkain101]

is your driveway sloped?

If so you may want to put the wheels you are working with on the high ground to cause the bubbles to flow to the bleeder more effectively.

[TheBigDog]

OK, here is the whole ugly story...

Back in May I was making an unplanned trip to Pennsylvania. It was late at night, and I had to get there and get back in time for work in the morning. As I was driving I noticed that my brakes got very soft. Very soft. Did I mention that the brakes got very soft? But they worked.

When I got home from work the next day I checked them out and found that I had damaged the left rear brake line and it had leaked all of the fluid from the master cylinder back. My next-door-neighbor is a Ford mechanic, and he gladly crafted a new brake line for me at work. Meanwhile I rented a car. He and I bled the brakes after he repaired the line and they were still soft, but functioning. We could not bleed them 100% properly because all of the bleeder valves were seized.

I ordered new front calipers and deprioritized doing any more work for a while. I did not order rear brake stuff because I did not want to do that work.

Then in June I was in a car accident. Now I know what you are thinking, it was because of my brakes. It was not, I would have hit that car anyway. Lets move on...

So when the truck gets back from the body shop after replacing the front bumper I finally decide to replace the front calipers. When I get them out fo the box I find that they are the wrong part, or at least the brackets that came with them are the wrong part, so I have to return them for a different brake kit. The work goes easily enough and I get to the bleeding. With the engine off the brakes appear fine at all four corners. Pressing the brake pedal it is nice and firm. Pumping makes it a bit firmer and lowers the level in the resevoir above the master cylinder by maybe an eighth of an inch; just a bit of air compressing in the lines. When you let off the level rises back up slowly as the bubbles expand again. This should be fine.

Then I turn on the engine and .... the pedal goes straight to the floor with no apparent resistance at all! Repeat procedure, same result. Frustration.

So then I call the all-knowing one (my father) and explain all of this. He thinks that either there is air in the rear brake cylinders themselves, or the master cylinder has a bad seal that cannot be felt unless the power assist is running. He suggests that I begin by replacing the rear brake cylinders (because only some kind of idiot would try and bleed the brakes from the input valve), and then if that did not work to look at the master cylinder.

So today I had the car towed to a shop to have a real mechanic work on it for me. I have been driving a rental for almost a week, this is the second time I have driven a rental related to these brakes. All in the name of saving me money by doing it myself.

Tomorrow I hope to be driving my truck again and the brakes will be like new.

Bill

[Cedars]

Originally Posted by TheBigDog

When I got home from work the next day I checked them out and found that I had damaged the left rear brake line and it had leaked all of the fluid from the master cylinder back. My next-door-neighbor is a Ford mechanic, and he gladly crafted a new brake line for me at work. Meanwhile I rented a car. He and I bled the brakes after he repaired the line and they were still soft, but functioning. We could not bleed them 100% properly because all of the bleeder valves were seized.



So when the truck gets back from the body shop after replacing the front bumper I finally decide to replace the front calipers. When I get them out fo the box I find that they are the wrong part, or at least the brackets that came with them are the wrong part, so I have to return them for a different brake kit. The work goes easily enough and I get to the bleeding. With the engine off the brakes appear fine at all four corners. Pressing the brake pedal it is nice and firm. Pumping makes it a bit firmer and lowers the level in the resevoir above the master cylinder by maybe an eighth of an inch; just a bit of air compressing in the lines. When you let off the level rises back up slowly as the bubbles expand again. This should be fine.

Then I turn on the engine and .... the pedal goes straight to the floor with no apparent resistance at all! Repeat procedure, same result. Frustration.

So then I call the all-knowing one (my father) and explain all of this. He thinks that either there is air in the rear brake cylinders themselves, or the master cylinder has a bad seal that cannot be felt unless the power assist is running. He suggests that I begin by replacing the rear brake cylinders (because only some kind of idiot would try and bleed the brakes from the input valve), and then if that did not work to look at the master cylinder.

So today I had the car towed to a shop to have a real mechanic work on it for me. I have been driving a rental for almost a week, this is the second time I have driven a rental related to these brakes. All in the name of saving me money by doing it myself.

Tomorrow I hope to be driving my truck again and the brakes will be like new.

Bill

Wheel cylinders leaking usually means fluid loss. Steady fluid loss.

Sounds to me like your master cylinder was weak and the cause of your soft brakes and it finally failed when your calipers began working properly