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Can't get a decent brake pedal despite all new parts

Tiny
SPEEDYLUBE
  • MEMBER
  • 1979 JEEP CJ7
  • 11,880 MILES
I have a 1979 CJ-7, 258 cu. In, 4 speed, manual brakes, factory disc front, drum rear. I have replaced literally everything; master cylinder, hard lines, hoses, calipers, bearings, hubs, rotors, pads, proportioning valve, wheel cylinders, drums, shoes, hardware, EVERYTHING. And I didn't cheap out either, I got the "better" parts, not the cheapest. I cannot get a decent, sustainable brake pedal. We have bled, and bled, and bled, almost 4 quarts run through the system. If you pump the pedal about 30 times, the pedal comes up about halfway (halfway decent pressure, not great), but if you take your foot off the pedal, count to five, and step on the pedal again, it slams to the floor. It has no leaks anywhere. My first thought was a bad reman master cylinder. I have already tried 3 reman masters and 1 brand new master, same problem every time. It has damn good fluid flow to all 4 wheels. I have been working on cars for a long time, but I am completely lost. I don't know what else to do!
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Thursday, May 17th, 2012 AT 3:26 PM

18 Replies

Tiny
RASMATAZ
  • MECHANIC
  • 75,992 POSTS
Go to this link: http://www.2carpros.com/articles/brake-pedal-goes-to-the-floor
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Thursday, May 17th, 2012 AT 3:47 PM
Tiny
SPEEDYLUBE
  • MEMBER
  • 20 POSTS
No air in the system. You can pump the pedal all day long, pressure bleed, and/or gravity bleed the brakes, no air bubbles at any wheel. And I have replaced the master cylinder 4 TIMES in the past 3 weeks, mainly because it acts like a master cylinder problem. 3 remanufactured master cylinders (from 2 different companies), and finally a BRAND NEW master cylinder. I run a repair shop, hence my screen name. I have been working on cars for 11 years. I have NEVER had a brake system be this problematic, not even new ABS brake systems. I have checked, double checked, and triple checked every line, hose, and part looking for ANYTHING that might cause the problem, I've found nothing!
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-3
Thursday, May 17th, 2012 AT 4:10 PM
Tiny
SPEEDYLUBE
  • MEMBER
  • 20 POSTS
I could see getting a bad master cylinder, maybe (and that's a big maybe) 2 bad master cylinders, but I very, very highly doubt I have gotten 4 bad masters in a row, especially considering that they came from 3 different companies now (1 NAPA, 2 Cardone, 1 Fenco).
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-2
Thursday, May 17th, 2012 AT 4:13 PM
Tiny
SPEEDYLUBE
  • MEMBER
  • 20 POSTS
In case I didn't mention it, this is a bone stock factory disc/drum system, nothing altered or otherwise fiddled with.
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Thursday, May 17th, 2012 AT 4:17 PM
Tiny
RASMATAZ
  • MECHANIC
  • 75,992 POSTS
Either the master cylinder is at fault or there's leakage somewhere in the brake system-brakes shoe adjusted properly and caliper pistons moves in and out-is the brake master cylinder push rod/adjusted properly-also investigate the inside mounting plate of the master cylinder
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-2
Thursday, May 17th, 2012 AT 4:24 PM
Tiny
SPEEDYLUBE
  • MEMBER
  • 20 POSTS
Okay, here we go. Master cylinder pushrod is made to the master cylinder, it is NOT adjustable, but it is the correct length (no play at the pedal). There is NO VISIBLE leakage anywhere, trust me, I've been through this system many times. The shoes are adjusted tight to the point where they are dragging a little, and the mechanical parking brake works like a champ. The calipers are where this gets interesting; I did not originally plan to replace the proportioning valve (with internal residual valves), but when I first replaced everything else, despite that fact that it had no pedal, the front brakes locked up (even with new calipers). Changing the prop valve fixed that. But that also tells me the calipers and sliders are working. When you pump it up and get the halfway pedal, it stops the front tires from turning; release the pedal, the tires spin freely. And back to the master cylinder. The odds of getting 4 in a row bad are astronomical. The odds are so incredibly high I'm almost willing to rule out the master cylinder as the source of this problem. Any other ideas?
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Thursday, May 17th, 2012 AT 4:36 PM
Tiny
CADIEMAN
  • MECHANIC
  • 3,544 POSTS
Adjust your rear brake shoes. So they are just hitting the drum. This can be done by adjusting the star adjuster through the window on the backing plate and a adjustment tool or by removing the drum and turning the star until it starts rubbing the drum. Ill be hear
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-2
Thursday, May 17th, 2012 AT 4:44 PM
Tiny
SPEEDYLUBE
  • MEMBER
  • 20 POSTS
They are already (and have been) adjusted correctly. When you spin the wheel by hand, you can hear the shoes rubbing the drums. At this point, if anything, they are probably a little too tight.
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Thursday, May 17th, 2012 AT 4:56 PM
Tiny
SPEEDYLUBE
  • MEMBER
  • 20 POSTS
And when I say no pedal pressure, I mean NO pressure. Not even a little. The pedal slams down all the way to the floor. I did notice this: If you pump the pedal quickly, you get the halfway pedal. When I say halfway, it seems to have a little pressure behind it about halfway down, but it is so-little pressure that with a little muscle you can still MAKE it go all the way to the floor. If you pump very slowly, you never get anything, the pedal travels all the way to the floor every time. This thing has manual brakes, without this little problem I am having, the pedal should be leg-tiring hard (my manual brake 1968 Chevy C10 will wear your right leg out when city driving).
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Thursday, May 17th, 2012 AT 5:03 PM
Tiny
SPEEDYLUBE
  • MEMBER
  • 20 POSTS
And again, I know it acts and sounds just like a master cylinder problem, but the same exact problem with 4 different master cylinders?
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Thursday, May 17th, 2012 AT 5:06 PM
Tiny
SPEEDYLUBE
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  • 20 POSTS
I forgot to mention before that every master cylinder I have installed HAS been bench bled before installation.
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Thursday, May 17th, 2012 AT 5:45 PM
Tiny
SPEEDYLUBE
  • MEMBER
  • 20 POSTS
A few days ago I talked to my favorite Jeep gurus at Morris 4x4 Center in Pompano Beach, Fl. They said that a manual C-3 Corvette master cylinder is a good upgrade for a Jeep CJ. I ordered one, and I have it here. I'm very tempted to try it, but I'm afraid I'll end up doing all that work again for nothing. What do you think?
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Thursday, May 17th, 2012 AT 5:46 PM
Tiny
CJ MEDEVAC
  • MECHANIC
  • 11,004 POSTS
OK FELLER

EVEN A NEW PART CAN BE BAD!

GRAVITY BLEEDING AIN'T GONNA CUT IT!

IF YOU NEED HELP ADJUSTING YOUR BRAKES, I CAN HELP W/ THAT TOO!

DISC UP FRONT OR DRUM ALL THE WAY AROUND, AS WITH EARLY '79s

BENCH BLEED AIN'T GOTTA BE ON THE BENCH---EZer ON THE JEEP!

THE FOLLOWING LINK WILL EXPLAIN HOW TO DO THIS STUFF---ABIDE BY IT 100% AND YOU RETURN WITH A SMILE.......STUFF YOUR PALS SAID, ERASE IT FROM YOUR MIND!

IF YOU INVESTIGATE THE LAST 2-1/2 OR SO YEARS BACK IN THE CJ 5 AND CJ 7 FORUMS HERE AT 2CAR......YOU WILL SEE I REALLY HAVE NO CLUE WHAT I'M TALKING ABOUT!

http://www.2carpros.com/questions/1999-ford-f-150-brakes--3

NOW

WE WANNA HEAR SOME GOOD NEWS

OR AT LEAST SOME IMPROVEMENT

I DON'T KNOW ABOUT THE REST OF 'EM, BUT AS LONG AS YOU ASK ***ANY*** CJ QUESTION AT THIS POST OF YOURS---I WILL CONTINUE TO ANSWER YOU.....TALK YOU THRU...SEND PICS

NOW THAT I HAVE JUST SKIMMED THRU THIS POST---I WILL GO BACK AND READ IT MORE THOROUGHLY

LAST THOUGHT---IS THE MASTER CYLINDER HOOKED TO THE TOP OF YOUR BRAKE PEDAL???????

THE MEDIC
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Thursday, May 17th, 2012 AT 9:17 PM
Tiny
CJ MEDEVAC
  • MECHANIC
  • 11,004 POSTS
OK--READ THRU ALL OF YOUR STUFF

THE OLE GRAVITY THING WITH A CJ, BLEEDS SO SLOW THAT AIR CONTINUALLY RISES UP IN THE LINES, AS THE FLUID TRICKLES BY....SORTA LIKE TURNING YOUR SHAMPOO BOTTLE UPSIDE DOWN AND WATCHING THE AIR INSIDE

I STILL HANG WITH DOING ALL THAT I SUGGESTED IN THE LINK I SENT IN MY PREVIOUS ANSWER

HERE IT IS AGAIN

http://www.2carpros.com/questions/1999-ford-f-150-brakes--3

YOUR TURN...I GOTTA KNOW!

THE MEDIC
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Thursday, May 17th, 2012 AT 11:50 PM
Tiny
CJ MEDEVAC
  • MECHANIC
  • 11,004 POSTS
OK BOSS---ANY PROGRESS?

YOU CAN'T JUST LEAVE US HANGING

DOING THIS IS LIKE BEING ADDICTED TO A "TOOL-TIME" SOAP OPERA.

THE MEDIC
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Saturday, May 19th, 2012 AT 8:43 PM
Tiny
SPEEDYLUBE
  • MEMBER
  • 20 POSTS
I got it fixed, brakes work great now. Wrong calipers. Some of the parts guys had asked me if it was a 2 bolt spindle or 6 bolt spindle. I didn't know what they were referring to (and still don't), and they couldn't answer my question either ("I don't know, man, that's just what the computer says"). Anyway, I even called my favorite jeep part supplier, and their tech guys couldn't answer me, so I gave up and ordered the stuff for a 2 bolt spindle. Wrong. Got the right stuff Thursday evening and almost immediately everything went to functioning correctly!
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Sunday, May 20th, 2012 AT 5:45 PM
Tiny
SPEEDYLUBE
  • MEMBER
  • 20 POSTS
Correction: some of the parts guys asked 2 bolt or 6 bolt spindle, some of them asked if it was a 2 bolt or 6 bolt caliper plate. Either way, I still haven't figured out what they are talking about.
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Sunday, May 20th, 2012 AT 5:48 PM
Tiny
DHELDOORN
  • MEMBER
  • 1 POST
I did a complete front disc brake conversion on my 77 cj7 and had the exact same problem. I can tell you with confidence that your calipers are on backwards. I took me hours of pumping to only dig deep into the system. I noticed that the bleed screws were on the bottom side of the caliper reservoir. I switched them from right to left and did the brake bleed one more time and WHAM! Problem solved. I was trapping air due to the bleed screw not being high enough to bleed the air out.

I purchased my new calipers from NAPA and I did not read the box to see the different part numbers. And by mistake I put the right caliper on the left side and left on the right. I hope this solves your problem. Don
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Friday, March 28th, 2014 AT 8:03 PM

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