Brake bleeding/problem question

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  #1  
Old 08-18-05, 09:42 AM
question1
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Brake bleeding/problem question

Hello,

Car is a 1994 Chev. Beretta, 5 pd. 2.2L, abs equipped. We have taken real good care of the car, bought new with 14 miles, getting close to 120k now.

Problem:
Brake master cyl. reservoir cap was off for other repair and brake pedal was "bumped" by a stray foot. Brakes have been alot weaker since this happened, all brake parts are in good shape. When the pedal was "bumped" I was under the hood and I did hear a very short "pssh" sound, I assume this was air getting sucked into the system.

Questions:
a)Will bleeding the brakes fix this problem?

b)During the bleeding do I keep the fluid level above the small hole inside the reservoir? Not sure but it seems that if the fluid is below this hole that is how air can enter the system if the pedal is pushed, Im not sure if that remains the same once a bleeder valve is opened so I am not sure how high to keep the fluid during the bleeding.

c)Could gravity bleeding the system fix this problem? I am a little worried about particles in the old fluid messing up the seals on the master cyl. pistons if the manual bleeding(pumping the pedal) method is used.

d)Do I need to bleed the master cyl. first before the brakes at each corner? I see what look like two bleeder valves on the master cyl. unit, and have been told by others to start the bledding process there.

I want to and need to do a full system bleed/flush, not only to fix the problem hopefully, but also because the fluid is original and in need of change, any help is very appreciated.
 
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  #2  
Old 08-18-05, 11:19 AM
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no problem

Did you open the brake system any place other than the cap on the reservoir?
If not, you do not need to bleed the brakes, and the sound you heard was vacuum left in the booster.

If you did open the system, you would need to bleed the system or at least that wheel anyway, so quit worrying about the "bump."

Air is compressible and makes the pedal feel soft/increased travel. Are you sure your brakes are "weaker" or do want to blame the "bumper" for a bad outcome?
 

Last edited by peabees; 08-18-05 at 11:23 AM. Reason: incomplete
  #3  
Old 08-18-05, 03:23 PM
question1
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System was only opened at the cap, I opened the cap so that I could push the pistons in the calipers back inward while changing what I thought was a bad axle that turned out to be the wheel bearing. Someone else got in the car while I was giving everything a once over and their foot bumped the pedal.

System has been weaker for sure, and there is increased pedal travel, braking is weak to the point that it is hard to get the car to dive into a corner, or if surprised by a red/yellow light it is sometimes hard to stop in time, again this fluid is original, the system has never been bled before. My other car is basically the same GM fwd chassis, and it stops like it should.

The car has h/d struts and shocks, Eibach springs, 215/45/17 rims with Dunlops, strut tower bar, and a couple other handling goodies along with x-drilled rotors and matching pads and handles really good, for awhile I thought the handling was going or alignment was off because I couldnt get through the tight corners as quick, then I realized its becuase of the brakes that I cant even get into the corner at speed like I used to.
 
  #4  
Old 08-18-05, 05:48 PM
Eddiebx
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although waht you described shouldn't have introduced air into the lines, i would definitely first try and bleed all the brakes out, so that you can rule out air in the lines before troubleshooting more.

and yes while you are bleeding make sure to keep the master cylinder level near full.
 
  #5  
Old 08-18-05, 05:57 PM
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No way you introduced air into the system in that manner. If you think you do have air somewhere, isolate the wheels one at a time by LIGHTLY crimping the flex hoses at the wheels. Gravity bleeding will normally do an excellent job on just about any vehicle. The bleeders you're talking about on the "master cylinder unit" I'm assuming are the ones on the ABS control. Those masters did not have bleeders. Not a good idea to mess with those unless you've actually serviced it.
 
  #6  
Old 08-19-05, 03:35 PM
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how do you gravity bleed? And while manual bleeding, and keeping the master cylinder level at full, won't the fluid be absorbing air the whole time?
 
  #7  
Old 08-19-05, 05:52 PM
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Brake fluid does not "absorb" air. Gravity bleeding is just as it sounds - take the cap off the master, open the bleeders, and let gravity do the work. Gravity "applies" exactly 14.7 psi of atmospheric pressure.
 
  #8  
Old 08-19-05, 07:10 PM
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Hey, thanks PM. So we're talking how long do I have to stand there adding fresh brake fluid? Also, do I open all four bleeders at the same time or one at a time starting from the one furthest away...? Thanks again!
 
  #9  
Old 08-20-05, 06:42 AM
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How long? As long as it takes - depends on what service was done I suppose. Method is up to you. Another plus when it comes to gravity bleeding - special sequences do not apply since you are not using the hydraulics to apply pressure. I always do them as you described, one at a time starting at RR and working up.
 
  #10  
Old 08-20-05, 11:06 AM
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Alright, forgive me for trying to get this right. So I bleed them one by one until I see the new fluid coming out the bleeder then I cap it and move on. If I gravity bleed it, no chance at me leaving air in my system? And it'll work just as well as if I did it manually? Also, when I asked how long, I was wondering if this was a deal that was going to take me 6 hours or something. I wanted to know if I was going to have to dedicate an entire day to this. That's all. Hey, sorry for being so particular, just trying to avoid a huge repair bill for messing up my brake line. Thanks!
 
  #11  
Old 08-20-05, 02:40 PM
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Like I said, time required will depend on service performed. I can't see it running more than 20-30 min. after a 4 wheel overhaul. After you have clean fluid at all 4 wheels, top off the master, replace the cap, and pump up the brakes. After that, remove the cap and hit all 4 wheels again for a few seconds each to "burp" them. I've done hundreds in this manner without a problem.
 
  #12  
Old 08-20-05, 04:33 PM
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darn it! You confused me again. Sort of. "Burp" them. You mean let a little fluid drizzle out of each bleeder then top off the master cylinder once more right? Or you mean, after you pump the brakes a lil something, there should be a few air bubbles at the tips of the bleeders I should introduce into the atmosphere? Or are both statements about right? Kinda sorta even? Sorry for being so anal here, I know it's annoying and I'm really not trying to be.
 
  #13  
Old 08-20-05, 05:23 PM
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Originally Posted by seancashmere
darn it! You confused me again. Sort of. "Burp" them. You mean let a little fluid drizzle out of each bleeder then top off the master cylinder once more right? Or you mean, after you pump the brakes a lil something, there should be a few air bubbles at the tips of the bleeders I should introduce into the atmosphere? Or are both statements about right? Kinda sorta even? Sorry for being so anal here, I know it's annoying and I'm really not trying to be.
Yes to all. Most times, there will be a bubble or two remaining and this will get rid of it.
 
  #14  
Old 08-20-05, 05:30 PM
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Perfect. Thanks a ton.
 
  #15  
Old 08-23-05, 05:53 PM
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One more question. Is it pretty much understood I should use DOT 3 or should I use something else? I drive a 2003.5 Mazda Protege5, 2.0 Liter, automatic. What do you think?
 
  #16  
Old 08-23-05, 06:55 PM
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Fluid type should be stamped on top of the mas cyl cap.
 
  #17  
Old 08-23-05, 08:11 PM
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coincidence.... is for the birds...

I truly hope bleeding off the system corrects your problems...... As I read your thread, I began to wonder..... I do not believe in coincidence....

You were changing out an axle, which turned into a wheel bearing problem..... removing the brake assembly in the process..... After repairs were completed, you had braking issues..... Poor at best.....

Again - I hope bleeding the system works for you.... but I would go back in and check my reinstall of the calipers/pads/shoes/etc.....
 
  #18  
Old 08-23-05, 08:15 PM
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Originally Posted by pmgheritage
Brake fluid does not "absorb" air. Gravity bleeding is just as it sounds - take the cap off the master, open the bleeders, and let gravity do the work. Gravity "applies" exactly 14.7 psi of atmospheric pressure.

brake fluid absorbs humidity in the air and every time you take the cap off the resevoir it drops the brake fluid's boiling point about 15 deg F. by the next day. i have an electronic brake fluid boiling point tester.

why i have this device i have no idea a company wanted me to test brake stuff for them on brand new products and they gave the $300 tester to me to. talk about random

he could have introduced air if the fluid level was low and the car was on jacks at an angle
 
  #19  
Old 08-23-05, 09:15 PM
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I figured it was something like that. That's the reason I was worried too about this gravity bleeding thing taking a long time. The longer it's exposed, the worse off I am. Really, my car only has a little over 25K on it, but I figured I'd bleed the brakes for longevity's sake. The way I see it, if I change transmission fluid every year, and change brake fluid every other year, along with changing my oil and filter meticulously, my car will be around for a long time. I haven't yet looked into the whole coolant/radiator thing yet. I'll be sure to read up on that sometime in the future and post on here some questions I have pertaining to switching out that stuff.
 
  #20  
Old 08-24-05, 04:14 AM
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Originally Posted by shottys
brake fluid absorbs humidity in the air and every time you take the cap off the resevoir it drops the brake fluid's boiling point about 15 deg F. by the next day. i have an electronic brake fluid boiling point tester.

why i have this device i have no idea a company wanted me to test brake stuff for them on brand new products and they gave the $300 tester to me to. talk about random

he could have introduced air if the fluid level was low and the car was on jacks at an angle
Humidity is moisture, which brake fluid is designed to absorb. If your $300 tester is showing that kind of a drop from removing the cap, either the fluid was already old and crappy, or it could also explain why the tester was "given" to you.
 
  #21  
Old 09-05-05, 06:15 AM
question1
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Just wanted to update the thread on my brake troubles, while in a fast food drivethru the brakes "gave out" and and the pedal traveled very close to the floor before I began pumping it and was able to stop, luckily there was no one in front of me and I only missed the pay window by a couple feet

After having the car available to me for a couple days I looked over everything more closely and found the drivers side rear drum backing plate and surrounding areas were wet from oil-ish looking fluid as well as finding marks on the inside of the rim of pooling fluid, bingo, now I knew I had a leak for sure and knew where it was at, spent $128 on new drums, pads and a new wheel cyl., got everything on and am now trying to get the system bled.

Using mostly gravity bleeding I have bled both rear sides into clear bottles, the fluid coming out at first was very dark/black, looks nearly like used motor oil, but not as thick, and had visible debris particles moving down the line.

I had a problem with the bleeder valve threads drawing in air on the rears, I got new fluid coming through the system so Im pretty sure that Ive got most the old fluid and air out, but I get a continous stream of bubbles along with the new fluid, the bleeder valve threads seem just loose enough to draw in air and I can see that they are just barely leaking a little fluid in return. While manually bleeding the continous stream of bubbles goes away as the fluid is forced through the valve and past the threads at the same time, hope that makes sense. After finishing the rear I started the car and very briefly tested things and the car came to a halt quickly from a very low speed as I pushed harder on the pedal, felt almost normal but still a little soft.

Going out this morning to gravity bleed the front(no partner to pump)and hopefully test drive with positive results, thanks for all the help so far, any more tips are appreciated.
 
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