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Thread: Brake Actuator Rebuild

  1. #1
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    Brake Actuator Rebuild

    How difficult is it to rebuild the brake actuator assembly/re-do seals? Mine leaks enough while it sits that I have to top it off every few weeks, but that's getting old. Remanfactured or sending it out to SCP to have it done is $600. Is there another option? Probably would end up being a winter project at this point, but I want to get some ideas.

  2. #2
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    Quote Originally Posted by 92SCtk View Post
    How difficult is it to rebuild the brake actuator assembly/re-do seals? Mine leaks enough while it sits that I have to top it off every few weeks, but that's getting old. Remanfactured or sending it out to SCP to have it done is $600. Is there another option? Probably would end up being a winter project at this point, but I want to get some ideas.
    Can you identify exactly where the leak is originating?

    The SC has a pressure switch down on the firewall that is used to trigger the ARC system...auto shocks. These are common leakers when they they get old. They are generally below the master cylinder, and can make it appear the MC is the leak source. They were hard to find for a while, but I think they've come back on the market, recently. The switch itself leaks thru the connector body.

    As well, the seal on the hydraulic pump motor can fail over time - it sits on the master cylinder assembly, right below everything else. Replacements aren't common, but some have used a Honda part, as I recall. The MC assembly has to come out of the car to do this.

    Another leak source is the o-ring on the accumulator. This seal can be sourced without too much trouble, just be sure to get the right type - info here via search. Accumulator R&R is not hard. Tips here via search.

    I haven't seen general leaks from the master cylinder body itself, but I'm sure they can happen.

    The difficulty in re-sealing the 'assembly' might be more about finding a proper kit, I think.

  3. #3
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    Quote Originally Posted by KMT View Post
    Can you identify exactly where the leak is originating?

    The SC has a pressure switch down on the firewall that is used to trigger the ARC system...auto shocks. These are common leakers when they they get old. They are generally below the master cylinder, and can make it appear that's the leak source. There were hard to find for a while, but I think they've come back on the market, recently. The switch itself leaks thru the connector body.

    As well, the seal on the hydraulic pump motor can fail over time - it sits on the master cylinder assembly, right below everything else. Replacements aren't common, but some have used a Honda part, as I recall.

    Another leak source is the o-ring on the accumulator. This seal can be sourced without too much trouble, just be sure to get the right type - info here via search.

    I haven't seen general leaks from the master cylinder body itself, but I'm sure they can happen.

    The difficulty in re-sealing the 'assembly' might be more about finding a kit, I think.
    Thanks for the reply, and the heads up on the ARC pressure switch. That never crossed my mind. Forgive me for ignorance, but does that switch run off the brake fluid? I only ask because I know what's leaking is brake fluid. The accumulator o-ring was one of my initial thoughts as well. I have to find some time to get underneath the car, and try to track where it's coming from. I "think" I've resolved some lingering cooling system issues I've had (whole other story) so my next move is onto this leak. Otherwise the brakes, and ARC system for that matter, work fine.

  4. #4
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    Yes, that pressure switch is inline and relies on brake fluid. It serves to signal the ABS controller when a hard stop has occurred, activating the shocks to firm.

  5. #5
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    Quote Originally Posted by KMT View Post
    Yes, that pressure switch is inline and relies on brake fluid. It serves to signal the ABS controller when a hard stop has occurred, activating the shocks to firm.
    Well, that gives me a starting point then. Thank you very much.

  6. #6
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    Sorry, I meant the 'ARC controller'. Automatic Ride Control, which works in concert w/the ABS controller/system.

  7. #7
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    No worries, I knew what you meant.

  8. #8
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    So I found the pressure switch, and it does seem to be my culprit. Through searching past posts on here, I've came across both the Ford and GM part numbers, but I haven't been able to find a definitive instruction on what the easiest way to swap in a new one is. Any advice? Is it as easy as disconnecting, unscrewing (with what?), and working backwards with a new one?
    1992 SC - 5 Speed, Black, Stock
    1991 SC - Auto, Black, Currently Stock

  9. #9
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    Quote Originally Posted by 92SCtk View Post
    Is it as easy as disconnecting, unscrewing (with what?), and working backwards with a new one?
    Pretty much, yes.

    Once you find a replacement, use it to size a thin open end wrench and have it ready to go in. Confirm there is a good/new o-ring. If you have to source your own, be sure it is brake fluid compatible.

    Disconnect the wire harness - the connector may be brittle from age, so be gentle, then use the wrench to loosen - once loose, continue to unscrew by hand, then act quick to swap it for the replacement so as to not lose more brake fluid than necessary.

    Screw it in by hand as far as you can, then snug it down w/the wrench. Clean out the connector as best you can, then couple it to the switch.

    If you're careful and don't leave the system open, you shouldn't have to bleed it later.

    Tidy up, check the level in the master cylinder and watch for leaks after driving.

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  10. #10
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    If you can't find a replacement part, you can just cap off the fitting with a bolt. Its an NPT thread.. not metric nor SAE. I don't have the specs, but if someone REALLY wants to know, I can go out and measure it.

  11. #11
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    Quote Originally Posted by TbirdSCFan View Post
    If you can't find a replacement part, you can just cap off the fitting with a bolt. Its an NPT thread.. not metric nor SAE. I don't have the specs, but if someone REALLY wants to know, I can go out and measure it.
    That depends on WHICH switch he's talking about.

    There's the motor run switch (turns the motor on when pressure drops low enough in the accumulator), and there's the ARC switch.

    You're talking about the ARC switch on the proportioning valve; I think the other posters have been thinking about the motor switch.

    RwP

  12. #12
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    Quote Originally Posted by RalphP View Post
    .....You're talking about the ARC switch on the proportioning valve; I think the other posters have been thinking about the motor switch.

    RwP
    I did see that there were a majority of posts that were referencing the motor switch, but this one is the ARC switch on the proportioning valve. Picture is of mine.

    I actually found TbirdSCfan's post from 2013 where he plugged it. I may go that route if it ends up being difficult to get. TBSCshop.com has a used one for $95, but I'd prefer it to be new if I can. See what I can find.

    Thanks for all the help
    Attached Images Attached Images  
    1992 SC - 5 Speed, Black, Stock
    1991 SC - Auto, Black, Currently Stock

  13. #13
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    Good morning


    I believe Super Coupe Performance sells the new Proportioning brake pressure switch for $49.99



    https://www.supercoupeperformance.co...ensor_300.jpeg


    New pressure sensor that is located in the brake line of the '89-92 Thunderbirds and Cougars with the Adjustable Ride Control Shocks.



    Comes with a new brake fluid compliant rubber O-ring.



    These sensors often break and/or leak brake fluid so we have you covered for a stock replacement!



    Shipping is free if your order total is over $50. If ordered individually shipping will be approx. $4-7.

  14. #14
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    If you plan to just plug it here's a link to the plug .

    http://www.mcmaster.com/#50925k337/=13oho6f

    -Tim
    Current Collection
    1994 Thunderbird SC - Auto converted to 5spd

    1995 Thunderbird SC - Auto

    1994 Thunderbird SC - 5spd
    1989 Thunderbird SC - 5spd - Daily Driver
    1990 Thunder/Cougar XR7 - 5spd
    1994 Thunderbird SC - 3v Project

  15. #15
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    Quote Originally Posted by sam jones View Post
    Good morning


    I believe Super Coupe Performance sells the new Proportioning brake pressure switch for $49.99



    https://www.supercoupeperformance.co...ensor_300.jpeg


    New pressure sensor that is located in the brake line of the '89-92 Thunderbirds and Cougars with the Adjustable Ride Control Shocks.



    Comes with a new brake fluid compliant rubber O-ring.



    These sensors often break and/or leak brake fluid so we have you covered for a stock replacement!



    Shipping is free if your order total is over $50. If ordered individually shipping will be approx. $4-7.
    Great call on that. I've ordered from Bill before so I'm familiar with the site, but I was looking in the brakes section rather than the suspension. Awesome. Thank you.
    1992 SC - 5 Speed, Black, Stock
    1991 SC - Auto, Black, Currently Stock

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