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    Finding exhaust leaks

    I've got a medium exhaust leak (doesn't sound like an open pipe, but a bit more than a tick like it used to be) and I'm sort of stumped.

    Stock duals, ancient downpipe/cats but newer H-pipe and tails.

    It appears to be at the cats at the farthest back.

    The previous owner thought it was where the air tubes enter the cats, but I've poked around there fairly thoroughly. It was crusty, but I can't find any holes.

    Ditto for the connections between the H pipe and the cat pipes

    I'm pretty sure it's not the manifold-head seal leaking, because it's not that loud in the engine bay. I haven't really rules out it being the connection from the manifold to the downpipe. I think it could also be leaking from the seal where the H-pipe meets the cat pipe, but with all the rust and the gaskets being oversized, it's hard to see. Could it be leaking from the seams of the cats?

    Are there any tricks to finding a leak? Something to put on and see if it melts? A telltale sign? I can't see any obvious carbon tracking, but it's hard to tell with all the damned rust.

    I've had it up on a lift running, but with the fan and noisy lifters and a generally noisy shop, I couldn't feel or hear anything.

    I really don't have money right now to throw at new downpipes, though I may be able to buy new universal cats if they turn out to be the culprit.

    85 4 door 351 Civi Crown Victoria - Summer daily driver, sleeper in the making, and wildly inappropriate autocross machine
    160KMs 600cfm holley, shorty headers, 2.5" catted exhaust, 255/295 tires, cop shocks, cop swaybars, underdrive pulley, 2.73L gears.
    waiting for install: 3.27's, Poly bushings, boxed rear arms, 2500 stall converter, ported e7's, etc

    06 Mazda 3 hatch 2.3L 5AT (winter beater that cost more than my summer car)

    #2
    Stuff something in the tail pipe. That will force exhaust out through any leak making it more obvious.
    2000 Grand Marquis LS
    2000 F150 XLT 6 inches of lift.
    1987 Bill Blass Mark VII - Sold
    1985 Mercury Grand Marquis Colony Park- SOLD. to a little old lady
    Mercury Owners Group member
    Save The Whales, Restore an Old Station Wagon!!

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      #3
      Thanks, I'll try that.

      I've heard of using tranny fluid down the throat of the engine in combination with that (then shutting the car off while it's still puffing smoke). Is this risky redneckery or a good idea (or both)?

      85 4 door 351 Civi Crown Victoria - Summer daily driver, sleeper in the making, and wildly inappropriate autocross machine
      160KMs 600cfm holley, shorty headers, 2.5" catted exhaust, 255/295 tires, cop shocks, cop swaybars, underdrive pulley, 2.73L gears.
      waiting for install: 3.27's, Poly bushings, boxed rear arms, 2500 stall converter, ported e7's, etc

      06 Mazda 3 hatch 2.3L 5AT (winter beater that cost more than my summer car)

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        #4
        that would kinda work, but it stinks. Engine oil does the same thing. Could foul the plugs, but thats about the worst thats likely to happen.
        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 grandpa spec white and cranberry

        1984 Lincoln Continental TurboDiesel - rolls coal

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

        Everything looks like voodoo if you don't understand how it works

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          #5
          I had a friend who fouled his o2 sensor doing that, thats the worst that could happen. If its cold out you could start her cold and look underneath and you should see were there is "seepage" of exhaust fumes.
          "Shakedown"- 1991 Grand Marquis GS Dual exhaust, Magnaflow xl turbos, Rear anti sway bar, Outlaw 1 wheels, 43k miles
          1985 GMC 1500

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