Loss of Vacuum Boost Braking Under Panic Stops - Page 4
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Thread: Loss of Vacuum Boost Braking Under Panic Stops

  1. #31
    Super Moderator Duece McCracken's Avatar
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    is boosting again, but that 5spd
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    Quote Originally Posted by Melchior View Post
    Mini update. I decided to do half the job today while I wait for the booster/MC to arrive in the mail. Glad I did - as expected, it took a little longer than the shop manual would have you believe.

    The MC isn't too much trouble. Getting the battery out is easy if you do the trick where you tilt the front panel forward. The battery tray is a bit of a pain. For anyone doing this in the future, I suggest you remove the air filter box and detach the wiring harness from the front battery tray panel by prying out the four push pins. With some elbow grease and really tilting the front panel forward, the tray just barely slides out without taking off the cowl. My MC was stuck to the spring inside the booster so I had to twist and firmly pull before it released.

    The booster, as predicted by the shop manual, is held in by four 13mm nuts. A 1/2" socket works too and is a bit tighter. I highly suggest you pick up a ratcheting wrench (ideally offset) for this job, as the upper left nut is a bear to access while routing your spine like a slinky and somehow fit two hands under the dash. I had a ratcheting wrench that clicks every 5 degrees and it was just enough to get the nut broken open to the point where you can finger loosen it. The other three nuts are accessible with a swivel and medium extension to a traditional ratchet.

    The brake pedal retainer pin was an absolute pain the @#$. You have to somehow compress the two locking tabs on the pin end so the pin can slide out, but there's very little room to get even a needle nose in there. I ended up grabbing the flat head side with a vise grip, rotating the pin so the two locking tabs were in line with the only angle in which I could get my needle nose to squeeze them. Then I squeezed as hard as I could with the needle nose, pushing it outward until the pin finally started to move. The vise grip I had on the other end was then enough to let me pull it out. Here's a picture of the retaining pin for reference:

    Attachment 359515

    The shop manual says to replace this, but it looks like it could be recycled since I didn't mangle it too much. I'll replace it anyway since it was cheap.

    With the booster's studs free of the nuts and the retaining pin removed, it slid off the firewall easily. The brake lines were a pain to work around since they're so rigid and you have to be careful. I ended up loosening the other end of the two brake lines with a crescent wrench so they could rotate (losing a minimal amount of fluid on the opposite end in the process), but that gave me just enough space to fit slide the booster out. If I were to do this again, I would consider removing the other end of the brake lines as well.

    Questions for the mind hive as I wait for my parts to arrive:

    - I lost a little bit of fluid in the line that feeds the clutch. Should I bleed/flush the clutch line when I flush the brake lines after the new equipment is installed? If so, any good writeups on how to do this? I don't even know where the bleeder screw for the clutch is. What order is this done in (before brakes, after brakes, etc.)?

    - Any good tips for bench bleeding our MC? I was going to use my mityvac and plug the other line, but the mityvac is an incredible POS and for the 15th time the pump pin fell out, this time it landed down a drain. I might pick up a pneumatic bleeder - can this be used for bench bleeding as well?

    - The FoST is new to me, so this is the first time I've had the battery disconnected. What needs to be done after re-connecting, aside from the obvious radio station resets. I seem to remember something about re-training the one-touch up/down windows.

    - Anything else I should be aware of when I go to install the MC/booster when they arrive?

    Thanks in advance. I am really hoping that this solves the braking issue.
    The way the MC is setup, bench bleeding isnt really an option. I just installed it and bled it on the car. Which most people do. No problems there.

    The clutch pulls at the halfway point of the resi, so bleed it after your brakes. Keep the resi full while doing this, due to the pickup location.

    I dont remember pulling that pin. I think i just took out the pedal assembly. Its been awhile. I should peek back under there. I have much more experience with the clutch master.
    Owner and lead tech of Duece's Wrenchworx. The one stop shade tree ST shop.

    Build thread - https://www.focusst.org/forum/focus-...-duecette.html

  2. #32
    FST Member Melchior's Avatar
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    Quote Originally Posted by Duece McCracken View Post
    The way the MC is setup, bench bleeding isnt really an option. I just installed it and bled it on the car. Which most people do. No problems there.
    Interesting. Why is that? I've never had to bench bleed a MC in any of my cars, so I don't have a comparative experience to reference.

    When mounted on the car, could I at least do a vacuum bleed of both ports with a mityvac or pneumatic bleeder to limit the amount of air in there before I reconnect the brake lines? I will have one of those cheapo bench bleeder kits with the plastic fittings available to me.

    Quote Originally Posted by Duece McCracken View Post
    The clutch pulls at the halfway point of the resi, so bleed it after your brakes. Keep the resi full while doing this, due to the pickup location.
    Do you recommend skipping a vacuum bleeder for the clutch, or traditional with a helper?

    Quote Originally Posted by Duece McCracken View Post
    I dont remember pulling that pin. I think i just took out the pedal assembly. Its been awhile. I should peek back under there. I have much more experience with the clutch master.
    Hmmm I don't think the booster can come out without the pin removed. The cabin side of the booster has a fork attached to the piston and the pin holds it attached to the brake pedal. Even if you took the pedal assembly off, it would have to pass through the firewall.

    I could be wrong, though.

    Thanks so much for your help.

  3. #33
    Super Moderator Duece McCracken's Avatar
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    Quote Originally Posted by Melchior View Post
    Interesting. Why is that? I've never had to bench bleed a MC in any of my cars, so I don't have a comparative experience to reference.

    When mounted on the car, could I at least do a vacuum bleed of both ports with a mityvac or pneumatic bleeder to limit the amount of air in there before I reconnect the brake lines? I will have one of those cheapo bench bleeder kits with the plastic fittings available to me.


    Do you recommend skipping a vacuum bleeder for the clutch, or traditional with a helper?


    Hmmm I don't think the booster can come out without the pin removed. The cabin side of the booster has a fork attached to the piston and the pin holds it attached to the brake pedal. Even if you took the pedal assembly off, it would have to pass through the firewall.

    I could be wrong, though.

    Thanks so much for your help.
    At that point you mine as well hook up the lines and bleed the whole brake system, which you have to do anyway. I do not recommend a mighty vac. Either manual with a check valve bleeder bottle, or a power motive brake bleeder. The power motive is the way to go. Like 55 bucks on amazon prime for the one with the cap we need. It works great, even on stubborn systems.

    You could power bleed the clutch, or go manual. I usually go manual with a helper. The bleeder on the clutch master takes like 3 full turns out before it starts to bleed, just a heads up.

    Now that I think about it, I just replaced the master and left the booster in the car, which is why I didnt deal with that pin. I remember painting a booster and my master cylinder, but that particular booster was for an E36 BMW. I tend to have a few projects going at a time, lmao. Gets hard to keep track.
    gemery likes this.
    Owner and lead tech of Duece's Wrenchworx. The one stop shade tree ST shop.

    Build thread - https://www.focusst.org/forum/focus-...-duecette.html

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  5. #34
    FST Member Melchior's Avatar
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    Quote Originally Posted by Duece McCracken View Post
    At that point you mine as well hook up the lines and bleed the whole brake system, which you have to do anyway. I do not recommend a mighty vac. Either manual with a check valve bleeder bottle, or a power motive brake bleeder. The power motive is the way to go. Like 55 bucks on amazon prime for the one with the cap we need. It works great, even on stubborn systems.

    You could power bleed the clutch, or go manual. I usually go manual with a helper. The bleeder on the clutch master takes like 3 full turns out before it starts to bleed, just a heads up.

    Now that I think about it, I just replaced the master and left the booster in the car, which is why I didnt deal with that pin. I remember painting a booster and my master cylinder, but that particular booster was for an E36 BMW. I tend to have a few projects going at a time, lmao. Gets hard to keep track.
    I have to tell you - I really dislike the mityvac. The pin that holds the piston to the pump handle constantly falls off and I've spent way too much time trying to find it when it falls. I'm very close to just buying a harbor freight pneumatic bleeder, but the power motive does sound tempting. I might end up just doing it the traditional two-person way, though.

  6. #35
    Super Moderator Duece McCracken's Avatar
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    Quote Originally Posted by Melchior View Post
    I have to tell you - I really dislike the mityvac. The pin that holds the piston to the pump handle constantly falls off and I've spent way too much time trying to find it when it falls. I'm very close to just buying a harbor freight pneumatic bleeder, but the power motive does sound tempting. I might end up just doing it the traditional two-person way, though.
    I was a bit skeptical of the power motive, until I ran into some issues manually bleeding. The PM took care of it really quick and easy. Not to mention it is now one person bleeding, the brakes and clutch. I highly recommend it. Especially at the level of maintenance you are doing, the reduced effort in labor is just phenomenal.

    Yeah, I like the mighty vac pro for testing vac lines and such, not for any bleeding operations, lol.
    Owner and lead tech of Duece's Wrenchworx. The one stop shade tree ST shop.

    Build thread - https://www.focusst.org/forum/focus-...-duecette.html

  7. #36
    I spend too much of my life on FST! gemery's Avatar
    is having a weekend fling with
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    Quote Originally Posted by Duece McCracken View Post
    The PM took care of it really quick and easy. Not to mention it is now one person bleeding, the brakes and clutch. I highly recommend it. Especially at the level of maintenance you are doing, the reduced effort in labor is just phenomenal.
    Another vote for Power Motive or other pressure bleeder. Some people have troubles with it, but they either abused the unit (cracks) or can't follow directions and thus use too much pressure (brake fluid squirts).
    Pepper was hatched from the dealer nest on 15 July 2018 after being laid by the factory in April 2018.

  8. #37
    FST Junkie! 20focusSTdriver17's Avatar
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    Just bought the motive w black label edition cap havent tried it yet.
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  9. #38
    Super Moderator Duece McCracken's Avatar
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    is boosting again, but that 5spd
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    Quote Originally Posted by 20focusSTdriver17 View Post
    Just bought the motive w black label edition cap havent tried it yet.
    Well get out there and bleed.

    Out of context, thats a cool line to say. Lmao
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  10. #39
    FST Junkie! rambleon84's Avatar
    is so mote be it
     

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    Quote Originally Posted by Duece McCracken View Post
    Well get out there and bleed.

    Out of context, thats a cool line to say. Lmao
    I aint got time to bleed
    Mod list here

  11. #40
    Supporting Member Blackula's Avatar
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    Quote Originally Posted by rambleon84 View Post
    I aint got time to bleed
    Sonuva b***h is dug in like an Alabama tick
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