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Thread: Help! Engine Hissing sound.

  1. #1

    Default Help! Engine Hissing sound.

    hello to all, i am new to this forum and am glad to come a cross such a website where everyone shows the love for these older boxed cars. I have an 87 Mercury Grand marquis LS when i purchased everything was working fine the AC was ice cold but now I find the air conditioner not working after looking threw out the motor i found a hissing sound the problem is i think a hose goes there but i do not know where it goes from there if anyone can please help me i would appreciate it and hopefully this fixes my AC problem. I attached pictures

    Thanks in Advance.
    Attached Thumbnails Attached Thumbnails IMG_0012.JPG   IMG_0013.JPG   IMG_0014.JPG   IMG_0016.JPG   IMG_0018.JPG  


  2. #2

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    The small exposed tubing nipple coming out of the smog pump that you show in your photos is most likely not the source of the hissing sound. My '89 Grand Marquis has the same exposed nipple and it does not have a hissing sound.

    More than likely, the hissing sound is from a vacuum hose that has come loose somewhere. It could be lots of places, but highest concentration of vacuum lines is up near the firewall and behind the dashboard. If the hissing sound is loudest inside the car, then it's most likely that the loose line is behind the dashboard. If the hissing sound is loudest in the engine bay, then it's most likely that the loose line is in the engine bay somewhere.

    There is no easy way that I know of to locate the source of a vacuum leak -- you just have to take your time and look for a loose line. You could also see if you can find someone more familiar with these cars, or cars in general, who is willing to try to help you find the source of the hissing sound.

  3. #3
    I'm an air-conditioned gypsy gadget73's Avatar
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    Thats supposed to be like that, strange as it may look.

    Whats your climate control doing exactly, is it blowing hot air out the defrost, or does it just not get cold? It could be a vacuum problem, or it could be the AC has a leak and needs to be repaired and recharged. Hot air out the defrost is a leak, but no cold air, but coming out of the dash where it should sounds like an AC problem.

    86 Lincoln Town Car (Galactica).
    5.0 HO, CompCams XE258,Scorpion 1.72 roller rockers, 3.55 K code rear, tow package, BHPerformance ported E7 heads, Tmoss Explorer intake, 65mm throttle body, Hedman 1 5/8" headers, 2.5" dual exhaust, ASP underdrive pulley

    91 Lincoln Mark VII LSC SE, triple black (Timewarp) - poly front bushings, KYB struts and shocks, Holley SystemMax1 lower intake, SilverFox AOD valve body,

    1984 Lincoln Continental TurboDiesel - rolls coal

    Quote Originally Posted by phayzer5 View Post
    I drive a Lincoln. I can't be bothered to shift like the peasants and rabble rousers

  4. #4

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    thanks for the reply guys hot air was blowing out the defrost before and i found the hose and got it fixed now it blows air out the dash but it is still hot air. regards to the exposed tubing nipple when i hold it with my finger i don't hear a hissing sound i thought a hose might have went there , i guess i need to take it in for service to find the real source of the problem. thanks so much!!!

  5. #5

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    I'm not sure what that nipple thing is on the smog pump, but it might be some sort of by-pass. My '92 Ford truck has a smog pump and the air actually is vented to the atmosphere after a cold start until the motor warms up. Then the air is routed to the catalytic converter. I think it has something to do with getting the cat to warm up faster, but I'm not sure about what the reason is.

    Perhaps that nipple thing is for a similar function -- to vent air to atmosphere. I don't know -- just a guess.

    By the way -- be careful sticking your fingers down there when the engine is running. You don't want to get any part of you or your clothes caught in any of the accessory belts.

  6. #6

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    by any chance what hose was busted? where was it?
    1986 Crown Victoria 302 Cold Air,Mac Shorty headers, Full Dual Exhaust with Super Forty Flows, Wagon Suspension with a Full Sound System Replacement 1/4 time 17.486 @ 77.43mph

  7. #7
    I'm an air-conditioned gypsy gadget73's Avatar
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    The nipple on the smog pump is a venturi. It creates vacuum for the cruise control when the engine is under heavy load.

    86 Lincoln Town Car (Galactica).
    5.0 HO, CompCams XE258,Scorpion 1.72 roller rockers, 3.55 K code rear, tow package, BHPerformance ported E7 heads, Tmoss Explorer intake, 65mm throttle body, Hedman 1 5/8" headers, 2.5" dual exhaust, ASP underdrive pulley

    91 Lincoln Mark VII LSC SE, triple black (Timewarp) - poly front bushings, KYB struts and shocks, Holley SystemMax1 lower intake, SilverFox AOD valve body,

    1984 Lincoln Continental TurboDiesel - rolls coal

    Quote Originally Posted by phayzer5 View Post
    I drive a Lincoln. I can't be bothered to shift like the peasants and rabble rousers

  8. #8
    302/430 newbie ald872000's Avatar
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    Question on that nipple thing on the smog pump

    IF I were to plug it up would I be hurting anything?

    Cause I got a rubber tube, attached it to the nipple and crimpt it

  9. #9
    I'm an air-conditioned gypsy gadget73's Avatar
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    it might actually start pushing air into the vacuum line instead of pulling a vacuum. It would effectively make a vacuum leak. Put it back the way it was originally.

    86 Lincoln Town Car (Galactica).
    5.0 HO, CompCams XE258,Scorpion 1.72 roller rockers, 3.55 K code rear, tow package, BHPerformance ported E7 heads, Tmoss Explorer intake, 65mm throttle body, Hedman 1 5/8" headers, 2.5" dual exhaust, ASP underdrive pulley

    91 Lincoln Mark VII LSC SE, triple black (Timewarp) - poly front bushings, KYB struts and shocks, Holley SystemMax1 lower intake, SilverFox AOD valve body,

    1984 Lincoln Continental TurboDiesel - rolls coal

    Quote Originally Posted by phayzer5 View Post
    I drive a Lincoln. I can't be bothered to shift like the peasants and rabble rousers

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