+ Reply to Thread
Results 1 to 11 of 11

Thread: Brake pedal to floor, but no visible leaks

  1. #1
    wh23g3g's Avatar
    Senior Member

    Status
    Offline
    Join Date
    Jun 2015
    Location
    Snellville, GA
    Posts
    484

    Default Brake pedal to floor, but no visible leaks

    So I went out for a drive this evening in my R/T. It's been sitting outside all week so I try to drive at least until it gets up to operating temperature since I don't use it as my daily driver. I recently had the leaf spring shackles, spring bushings, rear shocks, and sway bar links replaced last weekend. So technically it's been outside in the cold without being driven until last Friday evening. I just drove it about 20-30 minutes. I noticed right away the brake pedal was sinking to the floor. If you pump it when you're coming to a stop it firms up some. I took it easy, just decided to drive around some of the neighborhoods until I could check it out. When I pulled back in I did a brief inspection and didn't see any obvious fluid leaks from under the master cylinder, front lines, rear hose, calipers, or on the back of the drums. When I got a couple years ago, not even 10,000 miles, I did front calipers, rotors, hoses and checked the rear. The rears looked almost new. I saw some bare metal areas under the master cylinder but not wet fluid. Fluid is still full. Do the wheels need to be removed fully to see or would it be noticeable on the back of the drums if a cylinder was leaking? I can see through the wheels on the front and all over the front calipers. They are all dry. Pads are almost 95% full. I did add speed bleeders on the calipers when I changed them. Any ideas what to check next?

  2. #2



    Senior Member

    Status
    Offline
    Join Date
    Feb 2008
    Location
    Corrales, New Mexico
    Posts
    17,966

    Default

    Air in the lines.
    Open the bleeders and let them drip one at a time, just keep an eye on the fluid level. I have a Mighty Vac, but I still finish it off be letting them drip.

    Did I really say that on this forum?
    11.27 @ 118.23
    2017 NM Mopar Challenge Series Champion

  3. #3
    9t9-5.2's Avatar
    Home School Valedictorian

    Status
    Offline
    Join Date
    Jun 2014
    Location
    Central Iowa
    Posts
    1,307

    Default

    A master cylinder can go bad and not have an external leak.

    "Excuse me if I have some place in my mind, where I go time to time"

  4. #4

    Corey's Avatar
    GPz550 Addict

    Status
    Offline
    Join Date
    Sep 2009
    Location
    San Lorenzo, CA
    Posts
    1,926

    Default

    ^ Agreed, internal master cylinder failure will give a soft pedal like that of having air in the lines.

    This is a one-person brake bleeding tool I have used for years, from a company I use to work for. Gone are the two-person "Down. Open. Close. Up" days of brake bleeding.

    https://www.motionpro.com/product/08-0143





    ***Then I read you have speed bleeders.***
    DRTC #1176

    2000 Bright White CC (1/553)
    Dyno'ed 07/05/13 (126,000 Miles) 230 Hp / 308 Tq
    14.6 @ 93 mph (2.18 60 ft.), 4130 lbs.(1/2 tank gas)
    Truck Pictures --> http://smg.photobucket.com/albums/v9...Clough/Dakota/

    1985 Kawasaki GPz550
    2003 SV650S (Race)
    1973 W100 Powerwagon


    Mater: I don’t need to know where I’m goin’, I just need to know where I been!

  5. #5
    wh23g3g's Avatar
    Senior Member

    Status
    Offline
    Join Date
    Jun 2015
    Location
    Snellville, GA
    Posts
    484

    Default

    I checked again today when I could see outside. I didn't see any line leaks, cylinders, or calipers. I checked the junction block for the RWABS and didn't see anything either. I have a new master cylinder but I'm wanting to replace the brake booster while I'm at it because it's got corrosion on it where it appears the master was leaking years ago. I'm assuming the master cylinder apparently has been changed once before I got the truck. I swapped out the bleeders that came with the remanufactured calipers with the speed bleeders. I remember it was easy to bleed the brakes when I swapped out the bleeders. It didn't take long at all. So before I start taking off the master cylinder how do I know if one of those speed bleeders has failed? I know it has a built in check valve. While I'm at it, in 99 Dodge shows 2 different brake boosters with -TUT or +TUT. My build codes show neither one of those. But when I cross over the 2 different Mopar part numbers they all come up to the same Cardone 54-71902 booster. Are they all the same?

  6. #6

    98Dak408's Avatar
    Supporting Vendor

    Status
    Offline
    Join Date
    Jan 2009
    Location
    Detroit Area, Michigan
    Posts
    2,974

    Default

    You may have introduced air into the lines when changing bleeders and didn't get it all out when you bled the brakes. I would try bleeding the brakes again.

  7. #7
    wh23g3g's Avatar
    Senior Member

    Status
    Offline
    Join Date
    Jun 2015
    Location
    Snellville, GA
    Posts
    484

    Default

    I probably will try that while I wait for a new booster to show up. But I did put the bleeders on a couple years ago now, so that's why I was wondering why it all of a sudden got a spongy pedal. It did have some brake pull after putting on the new calipers. I always thought it may still need to be bled some more. But then I remember the second hand steering knuckles I had to find since my caliper mount threads were cracked. The second hand knuckles I got had the brake pad wear notches where the pads slide and they were pretty aggressive. I filed them down but of course they weren't perfect. Then I figured that's why there was a brake pull. I still haven't figured out the notches get into the slide area since the pad is sliding back and forth.

  8. #8

    98Dak408's Avatar
    Supporting Vendor

    Status
    Offline
    Join Date
    Jan 2009
    Location
    Detroit Area, Michigan
    Posts
    2,974

    Default

    But I did put the bleeders on a couple years ago now
    Oh, I misread. I thought it had been done recently.

  9. #9
    BIGROB's Avatar
    I killed Goose

    Status
    Offline
    Join Date
    Mar 2016
    Location
    Thibodaux, Louisiana
    Posts
    874

    Default

    Pumping the brake to firm up the peddle is more than likely a bad master cylinder or residual pressure valve which I think is in the proportioning valve. Air in the lines tend to feel spongy all the time. Of coarse a very small leak can cause that also and it might take a while to see fluid coming out of the drums. The shoes can absorb a fair amount before getting saturated. Since you recently banged around the rear end I'd pull the drums for a peak to be safe.

    Project Maverick. I feel the need, the need for speed

  10. #10
    wh23g3g's Avatar
    Senior Member

    Status
    Offline
    Join Date
    Jun 2015
    Location
    Snellville, GA
    Posts
    484

    Default

    Ok so today I changed the brake booster and master cylinder. I just got the brake booster this week but I've had the master cylinder for a little over a year on the shelf. The booster is AC Delco and the master cylinder is Centric I believe. I got everything changed out. I had to move the brake light switch to get to the top booster bolt. I bench bled the master cylinder a good while until there were no bubbles. I then installed it and noticed the it was leaking at the reservoir grommet on the back. So I took it out popped my original reservoir off and the new one. I noticed that the new reservoir was broken right at the grommet so that's why it was leaking. I cleaned my old reservoir up real good and put it on. It appears everything is holding. Began to bleed the brakes starting passenger rear then worked my way around. I've got speed bleeders. I wasn't getting much fluid coming out of the bleeders. But the pedal goes all the way to the floor. Is it because I had to swap reservoirs after I bench bled the master cylinder? I noticed the fluid wasn't going down much at all when I had the speed bleeders open and pumped the brakes. Anyway to purge it of air without having to undo everything? By the way I did notice some brake fluid in the old brake booster. So I'm guessing it failed internally.
    IMG_2497.jpg

  11. #11

    Default

    Had the same problem and I just bled the brakes to remove the air.

+ Reply to Thread

Posting Permissions

  • You may post new threads
  • You may post replies
  • You may not post attachments
  • You may not edit your posts
  •