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Thread: Possible vacuum leak under dash

  1. #1
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    Question Possible vacuum leak under dash

    Ever since I picked my GM up I've heard what sounds like a vacuum leak under the dash. While looking for the leak this last weekend I found it is coming from a white plastic piece wrapping half way around the shifter shaft. I have not pulled the part yet to see if it is cracked or something. The hoses connecting to it do not seem to be leaking and the sound seems to be coming directly from the plastic piece. The sound gets quieter when when I press the accelerator. The car idles fine and seems to shift fine. I cannot image that this thing is supposed to sound like it is leaking but I would hate to replace it to have the new one do the same thing. I question if it is actually bad since it does not appear to be causing any problems.
    '85 Mercury Grand Marquis
    only MSD multi-spark so far but hopefully a 351 on the way.

  2. #2
    Graham: Your source for car repair and smartassery. 91waggin's Avatar
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    There's a mechanism for the automatic parking brake release underneath the dash. I'd imagine that the thing on the shifter is the thing that tells it to release in forwards gears. The worst that happens if you seal the leak is that you'll have to release the parking brake yourself.
    Quote Originally Posted by gadget73 View Post
    There is nothing more permanent than a temporary fix.
    91 Mercury CP, Lopo 302, AOD, 3.08LSD. 3g upgrade, Moog wagon coils up front, cc819s in the back. KYB GR-2 police shocks. Energy suspension control arm bushings. Smog deleted.
    93 F-150 XLT, 302, Mazda 5-spd, 4wd. Stock for now
    99 Subaru Forester (wife's ride). 2.5 NA 5-spd. 95 Subaru Legacy Wagon--red--STOLEN 1/6/13

  3. #3
    The Brown Blob 87gtVIC's Avatar
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    What he said. From your description it sounds exactly like the parking brake release reservoir thingy. No biggie sealing off the leaks/lines.
    ~David~ Click the Pic for the Low Down on the Vic


    My 1987 Crown Victoria Coupe: The Brown Blob 0-60 in 8.43 sec, 1/4 in 16.75 sec @ 84mph
    My 2004 Mercedes Benz E320:The Benz

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    Thanks. Since I'm not using the e-brake until I have time to test it and fix it if it gets stuck I'll definitely just disconnect the piece for now. I've never had anything auto turn off the e-brake before, so I can't image I'll miss it any.
    '85 Mercury Grand Marquis
    only MSD multi-spark so far but hopefully a 351 on the way.

  5. #5
    The Brown Blob 87gtVIC's Avatar
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    lol Yeah it seems to be a pretty weird feature, most likely aimed at saving granny from smoking the brakes on her way to church Sunday morning.
    ~David~ Click the Pic for the Low Down on the Vic


    My 1987 Crown Victoria Coupe: The Brown Blob 0-60 in 8.43 sec, 1/4 in 16.75 sec @ 84mph
    My 2004 Mercedes Benz E320:The Benz

  6. #6
    fuck no, not today, thank you kindly 1990LTD's Avatar
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    Quote Originally Posted by 87gtVIC View Post
    lol Yeah it seems to be a pretty weird feature, most likely aimed at saving granny from smoking the brakes on her way to church Sunday morning.
    It seems useful in that respect but I'll be damned if it isn't a terrifying sound. I don't know if it's supposed to release slowly or just let go and spring back up, but it does the latter in my car, and I would've scared the shit out of myself if I didn't know about it and tried to set off with the brake on. That thing must've contributed to more than one cardiac episode
    - 1990 Ford LTD Crown Victoria P72 - the street boat - 5.0 liter EFI - Ported HO intake/TB, 90 TC shroud/overflow, Aero airbox/zip tube, Cobra camshaft, 19lb injectors, dual exhaust w/ Magnaflows, Cat/Smog & AC delete, 3G alternator, MOOG chassis parts & KYB cop shocks, 215/70r/15s on 95-97 Merc rims - Summer toy/work in progress.

    - 2007 Ford Escape XLT - soccer mom mobile - 3.0 Duratec - Daily Driver/Beater/Hauler of parts and contraband

  7. #7
    Graham: Your source for car repair and smartassery. 91waggin's Avatar
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    Mine goes bang and pops up really hard, just like that. Has since the car was new.
    Quote Originally Posted by gadget73 View Post
    There is nothing more permanent than a temporary fix.
    91 Mercury CP, Lopo 302, AOD, 3.08LSD. 3g upgrade, Moog wagon coils up front, cc819s in the back. KYB GR-2 police shocks. Energy suspension control arm bushings. Smog deleted.
    93 F-150 XLT, 302, Mazda 5-spd, 4wd. Stock for now
    99 Subaru Forester (wife's ride). 2.5 NA 5-spd. 95 Subaru Legacy Wagon--red--STOLEN 1/6/13

  8. #8
    I'm an air-conditioned gypsy gadget73's Avatar
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    Its not a gradual release. The vacuum motor pops the catch, same as if you pulled the release handle manually. You late model guys have that pump to release brake, but the early models had a handle to do that job. ka-bang when you release the brake.

    86 Lincoln Town Car (Galactica).
    Drivetrain: 5.0 HO, Explorer cam, FMS 1.72 roller rockers, 3.55 K code rear, tow package, BHPerformance ported E7 heads, Explorer intake, 65mm throttle body, Hedman 1 5/8" headers, 2.5" dual exhaust, ASP underdrive pulley, SuperCoupe stall converter

    Suspension: Bridgestone Protenza G019 225/60/16 on LSC turbines, 1 3/16" wagon front bar, 1" PI rear bar, cargo coils, KYB GR-2 front shocks, F150 rear air shocks, big front brakes, ES poly front suspension bushings, 00 CVPI steering box, ES poly body mounts, rear disc brakes

    91 Lincoln Mark VII LSC SE, triple black (Timewarp) - poly front bushings, KYB struts and shocks.

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