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    1. #1
      Join Date
      Mar 2008
      Posts
      88

      Brake pedal getting harder after driving for period of time

      I recently converted my.monye Carlo SS to manual brakes. I have been struggling with it ever since. Right now the pedal feels really really nice but the cars stopping is lackluster. I've driven it 3 times and every time I've driven it after a few miles I got to hit the brakes and notice the pedal feel is harder than at the beginning of the drive. The car has a big block and runs at a decent operating temp but there is a lot of underhood heat even with my cowl hood. Someone told me the pedal getting harder is due to air in the system. I have bled it several times and to be honest I hope he is right and that there is hope for it yet. I'd really appreciate any input or help. The car has been parked for almost 13 years and I'd really like to drive it again. Thanks in advance!

    2. #2
      Join Date
      Jan 2020
      Location
      Northern VA
      Posts
      60
      Country Flag: United States
      What size master cylinder are you using and what is the rest of your brake set up? Calipers/drums/brake line size? Did you move the brake pedal rod to the upper hole in the pedal?
      Air in the system will give you a soft pedal, not a hard pedal.

    3. #3
      Join Date
      Nov 2006
      Location
      Mountain Springs, Texas
      Posts
      4,488
      Country Flag: United States
      Sounds like you might have your pedal adjusted with a little pressure on the pushrod. Try backing it off a skooch.

      Manual brakes require aggressive pad compound unless you are a brake system designing prodigy… ��

      Don
      1969 Camaro - LSA 6L90E AME sub/IRS
      1957 Buick Estate Wagon
      1959 El Camino - Ironworks frame
      1956 Cameo - full C5 suspension/drivetrain
      1959 Apache Fleetside

    4. #4
      Join Date
      Mar 2008
      Posts
      88
      Hey everyone thanks for the responses I appreciate it. This is not a high end braking system by any means. It is a Monte Carlo SS with stock front disc brakes and stock rear drum brakes. Stainless braided hoses front and rear. After trying a 7/8" master cylinder I moved up to a 15/16". When I did this the car stopped better and the pedal improved. I moved the brake pushrod from the lower mounting point to the upper which gives me a 6:1 ratio. I have bled the brakes several times. I haven't had a chance to check it yet but I wondered if the push rod was to tight. I'm all ears unfortunately with my kids sports etc my time to work on it is very minimal. I agree about being a brake prodigy to get a system dialed in perfectly. A prodigy I definitely am not. Thanks for any help it's very appreciated.

    5. #5
      Join Date
      Mar 2008
      Posts
      88
      Quote Originally Posted by dhutton View Post
      Sounds like you might have your pedal adjusted with a little pressure on the pushrod. Try backing it off a skooch.

      Manual brakes require aggressive pad compound unless you are a brake system designing prodigy… ��

      Don


      Hey Don. An you recommend a aggressive pad that will work in this application? It's a street car so I can't run a pad that only works when it's hot. Thanks for the help

    6. #6
      Join Date
      Nov 2006
      Location
      Mountain Springs, Texas
      Posts
      4,488
      Country Flag: United States
      I would look for some ceramic brake pads on rockauto.com. Not sure there are other options for those stock brakes.

      Don
      1969 Camaro - LSA 6L90E AME sub/IRS
      1957 Buick Estate Wagon
      1959 El Camino - Ironworks frame
      1956 Cameo - full C5 suspension/drivetrain
      1959 Apache Fleetside

    7. #7
      Join Date
      Mar 2008
      Posts
      88
      Thank you don!

    8. #8
      Join Date
      Nov 2006
      Location
      Mountain Springs, Texas
      Posts
      4,488
      Country Flag: United States
      Quote Originally Posted by mc1984ss View Post
      Thank you don!
      I looked and I saw several high performance options. One was even carbon fiber based.

      Assuming your Monte is a 1984 based on your username.

      Don
      1969 Camaro - LSA 6L90E AME sub/IRS
      1957 Buick Estate Wagon
      1959 El Camino - Ironworks frame
      1956 Cameo - full C5 suspension/drivetrain
      1959 Apache Fleetside

    9. #9
      Join Date
      Mar 2008
      Posts
      88
      You are correct!

      Are the carbon fiber based ones more aggressive?

    10. #10
      Join Date
      Nov 2006
      Location
      Mountain Springs, Texas
      Posts
      4,488
      Country Flag: United States
      Quote Originally Posted by mc1984ss View Post
      You are correct!

      Are the carbon fiber based ones more aggressive?
      I can’t say for certain but the description says they have more stopping power.

      Don
      1969 Camaro - LSA 6L90E AME sub/IRS
      1957 Buick Estate Wagon
      1959 El Camino - Ironworks frame
      1956 Cameo - full C5 suspension/drivetrain
      1959 Apache Fleetside

    11. #11
      Join Date
      Jun 2001
      Location
      Newbury Park, CA
      Posts
      5,821
      Country Flag: United States
      Brakes are a fickle thing.

      Moving from a 7/8" ==> 15/16" will shorten the pedal travel but will require more foot force to achieve the same pad clamping force at the rotor.

      You mention that the brakes get hard after three applications. Are these three right after one another from a high speed?

      Tobin at Kore3 will have answers, and good ones. His advice is always spot-on. It may not be what you want, but it will be correct.
      VaporWorx. We Give You Gas http://www.vaporworx.com

    12. #12
      Join Date
      Mar 2008
      Posts
      88
      The 7/8" master cylinder actually stopped worse than the 15/16". This is backwards of how it should be correct? Makes me wonder if the 7/8" master was faulty. The brake pedal gets harder after driving for a while not after 3 stops. Almost seems heat related. I checked the pedal pushrod and I have plenty of slack in it. I made some temporary heat shields to see if that makes a difference but haven't had much time to work on it. I would love to pick Tobin's brain about it but I hate to be the guy to bother someone and not buy anything from them. I'm willing to spend money to fix it I just don't want to keep guessing and blindly throw more money at it. My SSBC brake pressure kit showed up and the adapters are machined terrible! I had to have the adapters fitting remachined and that's as far as I got. Thanks for the help everyone I'm all ears and I appreciate the help!

    13. #13
      Join Date
      Mar 2008
      Posts
      88
      Here's a small update. Drive it again last night without changing anything except some heat shielding. The pedal still got firmer after driving a while. Pulled it in the garage and immediately checked the brake pushrod, plenty of slack. I also lifted the front end to verify a sticking caliper or not, both spun freely. Next up new pads and pressure check. Still doesn't explain the pedal getting harder

    14. #14
      Join Date
      Nov 2018
      Posts
      642
      Country Flag: United States
      Have you tried changed the flexlines? They can deteriorate inside, and appear perfectly fine on the outside. The metal brackets that hold them in place halfway across can also rust up inside the bracket where the hose passes through, squeezing the hose where it passes through the bracket but again appearing perfectly fine on a visual inspection. Usually this causes a caliper to stick or sieze, but if it's not completely restricting flow I can see it causing these symptoms as the fluid passes easily under pressure but bleeds back out of the caliper slowly. The metal bracket is easy enough to check, pry it open enough to let the hose move through. You can examine the hose to see if it shows signs of being pinched here, and signs of rusty metal pressed into the hose.

      Also, when you bleed the brakes, how exactly do you do it? The only way I can ever get them to bleed right is when I use the "wife pump and hold the pedal" method. When I try using a suction bleeder I can never get all the air out.

      The only other thing I can think is the brake pedal. Cars that came with both manual and power brakes had brake pedals with two holes in them on the top bar. The different holes allow the pedal to provide a different stroke length for manual vs power brakes. Since I don't think the 80s Montes came with manual brakes, I doubt GM would have put a brake pedal in with both holes. You may need a new brake pedal with the longer manual brake stroke.

      2021 Durango R/T
      2005 Dakota beater
      2003 Dakota project-o-mobile

    15. #15
      Join Date
      Mar 2008
      Posts
      88
      Hey Vimes thanks for the response. I have Teflon lined stainless hoses on the front. They are pretty old but I thought this type of hose was good for life with any fluid type, I could be wrong. The lines do not pass through a metal sleeve.

      I also use the wife and the pump and hold method to bleed the brakes.



      My brake pedal does have two positions and I am using the upper position. I believe this ends up with a 6:1 ratio. Thanks again for the help


    16. #16
      Join Date
      Jan 2020
      Location
      Northern VA
      Posts
      60
      Country Flag: United States
      What brand master cylinder? Its been a while now, but I know wilwood had a recall on either the 7/8 or 15/16 master.
      Also, I believe that year monte had what's called quick take up calipers. I could be thinking of a completely different car though, so don't quote me on that. Or maybe it was a step-bore master. Its been many years since I did the manual brake swap on my wagon. Have you tried poking around on maliburacing.com? some pretty smart guys other there.

    17. #17
      Join Date
      Mar 2008
      Posts
      88
      Memory serves you correct, these cars did have the quick take up calipers on them. These are rebuilt replacements that are "not supposed" to be quick take up. From the factory they had a step bore master to deal with this.

      The master I am using is a Chrysler style master that I bought in a kit for the car. I've been a member at Malibu racing for at least 20 yrs! You are right lot of smart guys there

    18. #18
      Join Date
      Mar 2008
      Posts
      88
      finally got an update. after having to get the adapter fittings remachined from the ssbc pressure testing kit I was finally able to get it on the car. If I pump it a couple times and push the pedal ALL the way in really hard I can get about 650-700 psi at the front caliper. ! good average push of the pedal only gives me about 500 psi. From the little bit that I know this seems to low. I thought with disk brakes it should be around 900 psi? Any suggestions? Is this master junk also?

    19. #19
      Join Date
      Aug 2022
      Location
      SoCal
      Posts
      39
      I'm having my own issues with brakes, and also bought the SSBC kit with the garbage adapters. No idea how those pass any form of quality control. Fortunately, I bought a -3 to 1/8 NPT adapter at the same time so that I could directly hook to my braided flex lines.

      Anyway, on the topic of troubleshooting, you may want to check the pressure coming out of the master cylinder. That'll at least verify the master is good and that the problem is elsewhere. After determining that is good, take measurements at the end of the hard lines, the end of the soft lines, and block off one caliper at a time to find where the problem is. You'll need a few plugs/caps to do this.

    20. #20
      Join Date
      Mar 2008
      Posts
      88
      That ssbc kit is garbage!!! I even emailed them and told them about the products that I received. They responded almost instantly asking for pictures. I sent them pictures in all they said was thanks. I would have asked for new ones but I know I would have gotten the same garbage so I was fortunate enough to have somebody machine them for me. I put the gauge in a tee with a bleeder adapter that way I could bleed the pressure checking setup. I had thought about checking pressure at the master also I've been dealing with this problem for so long it's got another point where I don't even like looking at it. Please keep us filled in on your results thank you

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