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  •  » FYI Ford, Classic Mustang Tech Discussion
  •  » Rear disc brake conversion trouble.

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    11/25/2013 1:40 PM  #1

    Catheadlights
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    Registered: 7/31/2013
    Posts: 9

    Rear disc brake conversion trouble.

    So here is my problem. MS 2005-2010 rear disc brake conversion on an 8.8 rear, yea, I know, it was on an 8 inch prior. It is now mounted on the rear of axle. Is there a secret to setting the parking brake ?  I turned the pistons in all the way, put the pads in and mounted on the car, bled brakes and front works fine, rear brakes drag. I have a manual adjust proportion ing valve, I have not turned it at all, so there should be no residual pressure. The calipers are aligned correctly and there is plenty of space when I first put the loaded calipers on. They just drag, is it something with the e brake, or am I missing something?

     

    11/25/2013 3:10 PM  #2

    MS
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    From: Canyon Lake, Texas
    Registered: 1/24/2013
    Posts: 11,744

    Re: Rear disc brake conversion trouble.

    First, the adjustable proportioning valve should have nothing to do with residual pressure.  What about residual pressure valve in the master cylinder?  What MC are you using?

    Do you have the cables adjusted too tight?  There should be basically no tension on them when the ebrake is not applied.

     

    Money you enjoy wasting is NOT wasted money... unless your wife finds out.
     

    11/25/2013 4:11 PM  #3

    Catheadlights
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    Re: Rear disc brake conversion trouble.

    I am using everything from you, MS. The fronts are fine, but once the pedal is applied, the rears tighten, but then don't release enough, the wheels won't spin freely. So it may be the MC?

       •Thread Starter
     

    11/25/2013 5:02 PM  #4

    GPatrick
    Senior 24-7 FYI Addict

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    Registered: 4/01/2013
    Posts: 1,086

    Re: Rear disc brake conversion trouble.

    Any chance that your master cylinder push rod is too long and is not allowing the master cylinder to fully retract?  You could loosen the master cylinder bolts about 1/8" and see if the pressure drops on the rears.  Not sure if you are running power, etc.

     

    11/25/2013 6:03 PM  #5

    MS
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    From: Canyon Lake, Texas
    Registered: 1/24/2013
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    Re: Rear disc brake conversion trouble.

    Catheadlights wrote:

    I am using everything from you, MS. The fronts are fine, but once the pedal is applied, the rears tighten, but then don't release enough, the wheels won't spin freely. So it may be the MC?

     Which master cylinder did you get?   Do you have the ebrake cables hooked up?

    Money you enjoy wasting is NOT wasted money... unless your wife finds out.
     

    11/25/2013 6:39 PM  #6

    Catheadlights
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    Re: Rear disc brake conversion trouble.

    I have the 2000 mustang aluminium one. Yes the cables are hooked up, I took off any tension. The brakes just don't seem to release the right way. Power booster, prop valve, all exactly as directions state. I'm thinking about loosening brake line at MC and see if that release pressure.

       •Thread Starter
     

    11/25/2013 6:51 PM  #7

    KStang
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    From: Boise, ID
    Registered: 4/03/2013
    Posts: 93

    Re: Rear disc brake conversion trouble.

    Just a thought, are the lines connected correctly on the MC? Also, are there any pinched or sharp bends in the lines?

     

    11/25/2013 11:03 PM  #8

    MS
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    From: Canyon Lake, Texas
    Registered: 1/24/2013
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    Re: Rear disc brake conversion trouble.

    That MC is a disc/disc mc, so there is no residual pressure valve in it. No chance the prop valve is plumbed backwards?

    Just a thought, but this happened to me once...  The axle bearing retainer rings that press onto the axles were rubbing on the axle housing seals because the seals were not installed all the way in the housing.  The new bearings installed had thicker retainers than the previous bearings so it was not a problem until the bearings got replaced.  It made the axle drag like crazy and it appeared as if the brake was dragging.

    Another thing to check...  If you made all the flares in the brake lines, are you 100% sure there is a clean opening in the end of the flared tubing allowing full flow?  Sometimes if flares are not perfect, or the ID of the tubing was not 100% cleaned up prior to flaring, the tubing will shut off when tightened into the flare fitting.  It will pass enough pressurized fluid to actuate the brake, but not let the fluid backflow to the master cylinder.

    Also check the banjo bolts to be sure there is no blockage within the fluid transfer holes.

    Money you enjoy wasting is NOT wasted money... unless your wife finds out.
     

    11/25/2013 11:12 PM  #9

    Catheadlights
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    Re: Rear disc brake conversion trouble.

    Prop valve installed correctly. No probs with bearings, as wheels spin freely without brakes installed. Could be a line.

       •Thread Starter
     

    11/26/2013 1:31 AM  #10

    hmartin025
    I FYI 24-7

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    Registered: 4/01/2013
    Posts: 365

    Re: Rear disc brake conversion trouble.

    If the rubber flex line on rear is bad on the inside it can hold fluid pressure on calipers. check bleeders to see if that releases brakes, al least to figure out if its mechanical or hydrulic...
    Howard

     

     

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