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'soft' brake pedal


rmac-etc

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95 etc, 137 k

Had a lot of nasty repairs lately. shift solenoids, wheel hub assy's, drive axles, and the brake pedal has been going way too soft and deep. I need a weekend without a major repair!

So my brake pedal has been soft, as in going to the floor. I replaced the master cyl, it was 'bench bled', installed and I bled the whole system with a 'mityvac' (along with a drive axle and a ball joint which is another story). The brake pedal is still not right after all that. I did note that the driver side rear had a continual flow of bubbles as it was being bled. The fluid was drawn until clear, but the bubbles persisted. I do not think it was leakage around the vacumn tube as they appeared to be coming right out of the middle of the bleeder valve on the caliper into the tube. If you have not used a vacumn bleed device this may not make sense.

Either, I have not gotten all the air out, or it's getting in somehow, but there is no leak.

Ok, long story short, the brake pedal will go to the floor 'almost', after sitting a while, but will 'pump' up. The master cyl was replaced and the whole system has been bled with a mityvac, but the symptom persists. It can't allow air in without fluid leaking, right? And since there is no 'leak' I must be missing something obvious. Any advice appreciated....

thanks

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I'd dump that mityvac and go the old fasion way of bleeding your brakes. Never had success with it. You can bleed brakes yourself by propping a bar (I use my Club) between the seat and the brake pedal.

Air can enter the brake system without an obvious fluid leak. Air is comming in from somewhere. Have someone pump the brakes while you snoop around the brake lines from the master cylinder all the way back. You'll hear or see (bubbles) air passing through a joint. It could be a bad master cylinder or proportioning valve. Do it at a quiet place without cars, airplanes or wind around.

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jschunke,

I just purchased a one man bleeder from Advance Auto parts.

Plan to use it this weekend. This way I won't need to take all

the time opening and closing the bleeder and get someone

else to pump the petal. This particular product has a check valve.

I believe with it you can just pump the pedal and add fluid.

I didn't buy the vaccuum system because I know how difficult it

can be to keep a vaccuum on the system from the bleeder. Is there

any way you are pulling in air athe bleeder from a bad connection at

the bleeder?

mu .02 ;)

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Of course you can get air in at the bleeder because you have to unscrew the bleeder screw and air can get in between the threads. I've tried those one-man

bleeder check valves by Russel and tossed them out. It may be a pain in the butt bleeding the old way, but it works.

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Hi

I used a mity vac when I changed my brake fluid and bled the system. I also did get a lot of air bubbles in the drain tube when I was sucking the fluid out. What worked for me is you just have to crack the bleeder vavle very little so as not to suck air around the bleeder valve threads itself If that does not work I would try to use some plummers tape around the bleeder valve threads so you have a nice tight fit.

It does not take much vacuam to get the flow of the fluid maybe you just pumped up the vacuam press. too much. I noticed that when I did the first wheel I used to much vac pressure and that's when I would get air bubbles but after a few minutes I figured it out. I didn't have a low pedal mine is fine I still feel the old fashioned way is the best have someone hold the pedal down and crack the bleeder at the wheel. I used the mity vac because it beat having to use the wife as a helper pushing the brake pedal.If I didn't get it rite with the mity vac then I would have used the wife to assist but that's a shakey proposition at best I did it during the day so all my friends were at work i didn't want to wait until the late afternoon or weekend to do the job.I have used the wife before on other cars and that was an interesting 1/2 hr. to say the least..I finally had to put a block under the brake pedal and tell her to just hold the brake pedal on the block and let it up when I tell you imagine that BS for a 15 or 20 minutes....All in all I would use the mity vac again over the wife as a helper.

Good Luck

Jim

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i never had much success with the mighty vac when i used to do that type of stuff...same problem with the air getting sucked in around the threads...what i did to eliminate the bubbles, besides cracking the bleader very slightly, was to put some general purpose grease or wheel bearing grease around the bleader where it threads into the caliper...that seemed to help. jackg 90seville 94k

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So my brake pedal has been soft, as in going to the floor. I replaced the master cyl, it was 'bench bled', installed and I bled the whole system with a 'mityvac' (along with a drive axle and a ball joint which is another story). The brake pedal is still not right after all that. I did note that the driver side rear had a continual flow of bubbles as it was being bled. The fluid was drawn until clear, but the bubbles persisted. I do not think it was leakage around the vacumn tube as they appeared to be coming right out of the middle of the bleeder valve on the caliper into the tube. If you have not used a vacumn bleed device this may not make sense.

Either, I have not gotten all the air out, or it's getting in somehow, but there is no leak. 

Ok, long story short, the brake pedal will go to the floor 'almost', after sitting a while, but will 'pump' up. The master cyl was replaced and the whole system has been bled with a mityvac, but the symptom persists. It can't allow air in without fluid leaking, right? And since there is no 'leak' I must be missing something obvious. Any advice appreciated....

thanks

I wouldn't blame the vacuum bleeder. I use these all the time and

they will "not" introduce air into the system unless you do not know

how to use them. You will see air coming thru the vacuum hose

as you bleed each corner, as it sucks air past the threads of the

bleeder screw, but all that needs to be done is to allow the caliper

to gravity bleed for a little bit after you take off the vacuum

bleeder. Some people (including techs) do not do this, and then

wonder why they have a low pedal (still have air in the system).

There are some brake systems that just will not bleed properly

even with the vacuum bleeders. In those cases, manually bleeding

the brakes works well. Just have someone help you, do not pump

up the pedal first and then crack a line...crack your bleeder first

and then have your assistant push the pedal slowly to the floor,

holding it down until you have tightened up the bleeder screw.

Then release the pedal and repeat.

Depending on the model and it's ABS system, you might

even need to perform the automated bleed procedure, but

this does depend on the model and how much air has been

introduced into the system.

Ian

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You may not believe this, but the behavior has corrected itself.

What have I done that might affect it, well .... I did not open up the brake system anywhere. I did replace the left front halfshaft. In the process I removed the brake caliper, and hung it by a clothes hanger UPSIDE DOWN.

I can only surmise that an air bubble that I had not removed with the mityvac (probably operator error), moved in the caliper then when remounted escaped up to the master cylinder. Don't know it this is really possible, but its the only explanation that I can think of.

Whatever happened, I'll take it.

<_<

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I believe with ABS brakes there's an additional step you might be missing during the bleed process.

If someone has a service manual for your year of vehicle they might be able to get those pages to you.

I have the '92 Seville/Eldorado manual and IF the procedure on my manual will work for you, I'll happily scan the pages as a PDF file and post them where you can download them and review them.

Let me know.

If you really want to make people safe drivers again then simply remove all the safety features from cars. No more seat belts, ABS brakes, traction control, air bags or stability control. No more anything. You'll see how quickly people will slow down and once again learn to drive like "normal" humans.

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Thanks for the offer marika, but I am feeling the need to get my own darn manual .... :P ..

This forum should do a poll regarding geographic location. Some of us might be neighbors ( or close anyway) and could share special tools, methods and/or advice face to face ...

I am pretty certain there is a bay area contingent ...

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Hey ... our posts are being auto-edited. The previous post says 'darn manual' ... well guys, that ain't what I wrote!!!!

The word 'darn' hasn't escaped my lips (or fingers) for, oh ..... ever since radial tires were the next big thing!

:lol:

(anyone want to test out the other six G Carlin 'dirty' words ... oh, wait, the one I typed in wasn't even one of the original seven !!! gasp)

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I think it's a good idea for everyone to put their city in their profile. That way if we find someone close to where we live, we might then be able to share special tool, etc.

Jeff

Jeff

98 Concours

90 Seville

04 Corvette

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I just got back from the mechanic who bled the entire system and replaced all the fluid. It needed it. The fluid was brown and pretty much at the end of it's service life.

Car actually brakes better now. I don't have to press hard on the peddle anymore.

If you really want to make people safe drivers again then simply remove all the safety features from cars. No more seat belts, ABS brakes, traction control, air bags or stability control. No more anything. You'll see how quickly people will slow down and once again learn to drive like "normal" humans.

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I've already "met" two on this site. One right down the road and another about :30 min away. Adding location to your profile would be nice, unless of course your in the wittness protection program.

:re auto-edit, I noticed that some tima ago when I typed "hell". Maybe the quotes will defeat it this time. The politicaly correct term apperantly is "heck".

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