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

 

Is your Check Engine light coming on?

Do you know where the leak is?

 

The check engine light isn't coming on and I don't know where the leak
is.

 

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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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'

 

Then how do you know it's the manifold?

 

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

 

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.

 

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.

 

I have no confidence in those muffler shops Curly.

 

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.

 

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

 

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