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fixitgayle
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Dec 28, 2009, 12:45 PM
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Brake Problems
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I need help. I have Chevy 96 c-1500 2wd with a v6 and automatic. The brake petal slowly goes to the floor. No leaks and a new master cylinder. It was doing it before the new master cylinder.I had to hit the brakes hard in reverse and next time they went to the floor. Without engine running you can hear master cyl bubling. I did bench bleed the master cylinder before installing.
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Sidom
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Dec 28, 2009, 6:04 PM
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Re: Brake Problems
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These system aren't known for their firm brk pedals but also shouldn't go all the way to the floor...
On quick question.
Since that reverse incident, have you removed all 4 wheels and done a complete inspection of the whole system?
(This post was edited by Sidom on Dec 28, 2009, 6:05 PM)
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fixitgayle
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Dec 28, 2009, 6:15 PM
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Re: Brake Problems
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Other than changing master cylinder and a general look over, no. The thing that bugs me is the bubbling back thriough the master cylinder.
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Sidom
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Dec 28, 2009, 7:26 PM
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Re: Brake Problems
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Those can be a little tough getting the air out, I'm assuming you bled out the whole system, if not it really needs to be done..... If you are having a helper pump the pedal, the trick on this system is to pump the pedal very slowly... Pressure or vacuum bleeding would be the best way to go.....
As for the other thing... Just for peace of mind, the rest of the brakes really do need to be inspected to make sure nothing came loose when you had to jam on the brks.........
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fixitgayle
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Dec 29, 2009, 3:21 AM
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Re: Brake Problems
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I will start in that tonight when I get off work and see where that leads me. Thanks, I'll let you know what happens
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fixitgayle
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Dec 29, 2009, 7:18 PM
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Re: Brake Problems
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Well I am getting nowhere fast. I decided to try a new booster. No luck there. I took all 4 wheels off and bled the brakes. No problems found and still no luck. Unless it is something in the antilock system I am out of ideas 
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Loren Champlain Sr
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Dec 29, 2009, 7:47 PM
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Re: Brake Problems
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gayle; I've been hesitant to jump in, here, but....If you are getting 'bubbles' in the master cylinder when pumping the pedal, you haven't got all of the air out of the system. The rear brake adjustment has a definite effect on the pedal height. Bleed the master cylinder, one line at a time, until you are certain that all of the air is gone. Adjust the rear brakes as needed. Then, bleed all four wheels, starting at the passenger rear wheel, driver's rear wheel, passenger front, then driver's front...in that order. The brake booster has nothing to do with pedal height. All it does is 'assist' the 'foot' pressure to the pedal. Whether or not the engine is running, you should have a good, solid, pedal.
Loren
SW Washington
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fixitgayle
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Dec 30, 2009, 3:37 AM
Post #8 of 25
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Re: Brake Problems
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Thats the order that I bled in ,starting at the farthest point and working to the closest and did not get any air out. The petal just goes slowley to the floor and pumping the petal does not eliminate this. I have never encountered this before in a vehichle. The brakes start working as soon as you press the petal, but the petal just fades away. Thanks for all the help here by the way.
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Tom Greenleaf
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Dec 30, 2009, 8:36 AM
Post #9 of 25
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Re: Brake Problems
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You have the gang on this! If brake pedal can fade to floor with steady pressure you might have a defective master cylinder! It does happen. I don't think air alone would cause fade to floor but an even spongy pedal.
I've had a few new defectives and more so with rebuild ones (master) and will pay for new for anything I own and strongly suggest it for anyone - My opinion.........
T
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Sidom
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Dec 30, 2009, 11:27 AM
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Re: Brake Problems
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I'm not there and you may be doing this correctly but this is overlooked a lot, so I'll say it again......You have to pump the pedal.....very slowly on these systems.....If you pump like normal you aren't going to get the air out. Start at the master & bleed each line (while the helper pumps slowly and the go from there....
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Tom Greenleaf
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Dec 30, 2009, 6:51 PM
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Re: Brake Problems
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Good article Sidom,
I notice especially when cold, even brake fluid is thicker viscosity and too fast just sucks air back in from lines. It was in there - helper must hold steady with pedal till bleeder is closed or it's start over again!
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ratrace2
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Dec 30, 2009, 8:32 PM
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Re: Brake Problems
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If there are no brake line leaks. . . . . ."Fade to the floor" is a bad master cylinder. . . .Buy NEW. . . .always. . . .
(This post was edited by ratrace2 on Dec 30, 2009, 8:34 PM)
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fixitgayle
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Dec 31, 2009, 7:38 AM
Post #13 of 25
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Re: Brake Problems
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That is one of the problems, It is a NEW master cylinder. The only reason for the booster change is one of the guys I qork with just had his go bad on a 98 c1500 and it had the same symptoms,but he did say that he could hear the vacuum leak when it went bad.
I am off today and going to explore more and see where I end up, I will keep all posted of results as this is a very strange one.I do agree that new is always the way to go one a brake system repair.
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Tom Greenleaf
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Dec 31, 2009, 9:41 AM
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Re: Brake Problems
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Too bad about the booster if it didn't need it You can test them to know. You should have power assist for at least one good feel with engine having been off for a while - days if perfect. A check valve could fail and give you various amounts of assist.
Master new or not could be bad. Not many but I had two in a row found to be one place had a spec wrong - all recalled after lots of hair loss. If you come to a strong conclusion that's it definitely don't get the same brand.
T
(This post was edited by Tom Greenleaf on Dec 31, 2009, 9:46 AM)
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fixitgayle
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Dec 31, 2009, 3:39 PM
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Re: Brake Problems
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One of the guys I work with is looking at the truck for his 16 year old son, so at least I know he won't have problems with the brakes,IF I ever get them fixed. WHile looking over again today I noticed the bront brake hoses didn't look the best so I picked up a set and put new bleeder valves in the front as well. BLed very carefully and slowley and only gor air out of front line as it should have been. I STILL have the same problem. I am going to take the master cylinder back Sat morning and get another one. I'll keep you posted. I hate to get new bad parts,especially when you are working on a really strange problem to start with.
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Sidom
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Dec 31, 2009, 3:46 PM
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Re: Brake Problems
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One quick test you can do. Carefully pinch off the brk hoses one at a time and check the pedal. If you pinch off the back hose & get a good pedal, the problem is in the rear. Try pinching off both frt hoses if the pedal get firm, the try one at a time to try to narrow down which side it is.........
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fixitgayle
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Dec 31, 2009, 3:53 PM
Post #17 of 25
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Re: Brake Problems
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I'll try pinching the lines tomorrow. SHould I be able to use a vise grip clamp to do this?
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Sidom
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Dec 31, 2009, 4:18 PM
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Yes if you're careful enough. I'm always leary about doing this, especially on older hoses just for the fact that you can wind up restricting the hose. So you want just enough pressure to block the flow but trying not to damage the hose....
Did you try to rebleed the master at the lines using that posted procedure?
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fixitgayle
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Dec 31, 2009, 6:20 PM
Post #19 of 25
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Re: Brake Problems
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No but I will tomorrow. I also have a 95 4X4 suburban and the master cylinder makes the same noise when applying the brakes when not running so I think that part is normal just fluid moving around in the resvoir.I will be carefull with the lines though.Thanks
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Tom Greenleaf
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Jan 1, 2010, 9:24 AM
Post #20 of 25
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Just a wild thought: Is there any chance an oil (instead of true brakes fluid) ever had a chance to get in this system?
Brake rubber parts do NOT tolerate oil! They quickly would do bizarre things and probably end up leaking somewhere. The rubber would swell up.
It's a maybe for situations that are difficult to diagnose,
T
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fixitgayle
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Jan 2, 2010, 3:36 PM
Post #21 of 25
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Don't see how oil could have gotten into the system, I have had the truck since early last year and have had no problems at all. I took the master cylinder off today and am going to get another one while I am at work Monday,Good thing this is not my primary ride.
I will post results when I get new Master cylinder on.
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Tom Greenleaf
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Jan 2, 2010, 4:48 PM
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Again on oil in a brake system: Most issues seem to stem from a plain mistake topping off a master cylinder. Brake fluid (plain DOT3)is water soluble and a big word 'hygroscopic' (absorbs moisture) - alone a tad of that isn't an issue. For whatever reason all rubber parts, master cyl, proportioning or multi valve, calipers, flex rubber hoses, calipers and if applicable wheel cylinders would all need replacement. The good news is if you make the mistake, oil floats on brake fluid and if quick suck it out quick with a turkey baster before it can enter system.
I don't want to bash the speedy oil change places but the so called 10 minute oil service wreaks of havoc and TMK the workers may have (don't know as I wouldn't take a shopping cart there but went thru one once with someone with a company car and 3 qts too full later had to fix that!) - long ago but they used a want with buttons that counted volume like a bartender's thing if you've seen one. The places buy in such volume the filters are literally a buck! The workers at ones I know of are NOT full techs which of course would cost more and worth it IMO.
The problem if at all possible in history of vehicle would take some time. One week or much longer - as said an oil product floats at the top. Bleeding that thru would be enough to cause a brake holocaust!
If you are sure then just archive this reply as to what happens. You would see the rubber gasket of top of master cylinder showing effects if so. It would bloat.
Just know this site is here - free to use by some of the most impressive techs here and willing for no pay to get you thru an issue and of course brakes are #1 - I don't care if it doesn't run so much but ability to stop is paramount!
Moderators - send this problem to another site if you feel better suggestions are available elsewhere - here to fix nasty screwed up stuff no matter what it takes! BTW - can say all guys at the moment - high level techs here!
TomG
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fixitgayle
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Jan 24, 2010, 12:20 PM
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Tom and rest of the guys. Sorry about lack of reply till now BUT I do have information. After going nuts I hada friend who runs garage look at it for me and we went thropugh all the steps and still no results. I ordered a used brake anti lock eloctronic control module and that was the problem. I new it had to be something oddball so just put this in ths info locker till needed again. Thanks for all the help and concern. It is nice to have a group of people willing to help us out.
Gayle
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Sidom
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Jan 24, 2010, 12:45 PM
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Glad you finally got your brk problem fixed and thx for posting the fix.
You are correct this is valuable info and you may in fact help someone out down the road
(This post was edited by Sidom on Jan 24, 2010, 12:46 PM)
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Tom Greenleaf
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Jan 24, 2010, 12:47 PM
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Thanks Gayle for the report on the fix. Not a fan of used brake parts except metal items perhaps that broke. It's not legal here TMK but if they are up and working, feeling proper than I'll shut up,
T
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