Exhaust Mainfold Leak

Hello All. I'm new to this group so please go easy on me.
I've got a 2000 civic which has an exhaust manifold leak. I've owned the car for a couple of years and I think it's always been there, just
getting slightly worse with age.
I'm wondering what sort of damage I'm doing to the car, if any, and also what the cost would be to repair it. I'm in the Toronto area of Canada if that helps.
Thanks in advance for any comments.
Peter H
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Is your Check Engine light coming on?
Do you know where the leak is?
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TeGGeR

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The check engine light isn't coming on and I don't know where the leak is.
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Then how do you know it's the manifold?
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I had the car in for an oil change and the guy recommended that he add this compound to the engine to clean it out. He propped the hood open and hooked up this bottle of goop. When I fired up the engine some smoke came out from under the hood and the guy doing the work made the diagnosis. This was one of those rapid oil change places and I realize that the workers there have limited knowledge of the vehicles that they work on, but this guy was in charge of the shop and I have some confidence in his knowledge.
I've also noticed it is noisy when first started and then settles down once it's warmed up.
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Are they sure they didn't just spill some oil on the exhaust or something?
Sounds like pretty flimsy evidence on which to spend money replacing an exhaust manifold. If the crack is big enough to emit smoke, it will be big enough to emit noise.

That sounds like piston slap, not a manifold leak.
If I were you, I'd get a second opinion on that "cracked manifold" thing.
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Smoke isn't a common indication of exhaust leaks. Although start-up smoke can be in the exhaust from leaky valve seals, getting enough of that exhaust out into the air would require a leak large enough to produce a terrible roar. Small leaks normally suck air in rather than blow exhaust out.
Typical exhaust leaks from the manifold area have a distinctive sound. The sound is a distinct tapping sound that we'd never think was an exhaust leak unless we knew it already; it sounds exactly like a small metal part tapping against a larger metal part. The sound is like a noisy lifter but a bit sharper, and unlike lifters, wrist pins and rod bearings it gets noticeably louder when accelerating. Piston slap sounds similar (including the loudness when accelerating and quieting down as the engine warms up) but isn't as sharp. Note that the quieting with warm-up doesn't usually apply to cracks, just to leaks where the manifold is bolted to the head.
The only certain diagnosis is to locate the leak.
Mike
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Thanks to all who replied. It sounds like the guy at the lube shop spilled a bit of oil on the motor and when it smoked he blamed it on an exhaust manifold leak, or perhaps he noticed the sound, believed it to be a leak and mentioned it to me at the same time as a bit of oil was spilled, which caused the smoke. I assumed that the smoke and leak were connected.
I do hear a tapping when the engine is cold and it does sound like a smaller piece of metal hitting a larger one.
I'll take it into a shop for a diagnosis. It's time for an oil change anyway.
Thanks again for the great advice.
Peter H
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What you hear is a tick when the engine is cold, stronger as you open the throttle, and quieting down within a minute or two?
My favorite method for finding exhaust leaks uses a shop vac. Starting with a cold engine, duct tape the hose to the exhaust pipe and connect the other end to the exhaust side of the vac. (It is better if you were able to run the vac to blow any excess grit out before connecting it to the car.) Turn on the vac and feel around for the air blowing out. It's a surprisingly strong stream of air even for a small leak.
Mike
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Peter H wrote:

damage depends on where it's coming from. if it's a leak from under the manifold/head gasket interface, it can cause expensive damage. if it's simply a cracked manifold, [most likely], further damage is probably trivial beyond the need to spend $$$'s on replacing the thing. just drive until noise/fumes/emissions become an issue for you.
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Peter H wrote:

------------------------------------
So, you can tell it's leaking because it's noisy when you start it cold, but it gets quieter as it warms up? It won't set a CODE for that, but a leak under the hood could be a bit dangerous on a long highway drive. Carbon Monoxide. Why not just ask a muffler shop to look at it for free?
'Curly'
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I have no confidence in those muffler shops Curly.
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Also keep in mind that an exhaust leak allows air to enter the exhaust and the 02 sensor will read the extra oxygen and try to lean out the fuel mix to compensate , resulting in possible driveability issues.
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