Finding exhaust leak under hood

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Masospaghetti - 30 Jun 2006 05:22 GMT

Hi all - car is a 1985 Corolla SR5, 224k miles.

When the engine is first started, even if it's not fully cold, I can
hear some exhaust noise from under the hood, primarily when
accelerating. What would be the best way to pinpoint where it is? It's
definitely under the hood somewhere. It goes away after a couple of
minutes of driving.

Thanks all

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Don - 30 Jun 2006 05:30 GMT

>Hi all - car is a 1985 Corolla SR5, 224k miles.
>
>When the engine is first started, even if it's not fully cold, I can
>hear some exhaust noise from under the hood, primarily when
>accelerating. What would be the best way to pinpoint where it is?

I would use a smoke machine leak tester. But that an expensive piece
of equipment. You can slowly pour some ATF down the intake and the
resultant smoke will show you the leak. Probably a cracked exhaust
manifold.

Don
www.donsautomotive.com

> It's definitely under the hood somewhere. It goes away after a couple of
>minutes of driving.

When the manifold gets hot and expands the crack typically closes.

>Thanks all

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tom@rockauto.com - 30 Jun 2006 15:05 GMT

Since the leak only happens when the car is first started, both hot and
cold, it could be the EGR valve or gasket that is leaking. That is one
of the exhaust system parts that might cycle on and off every time the
car is started. Here is a photo of the EGR valve from the Emissions
section of the www.rockauto.com catalog so you know where to listen:
http://www.rockauto.com/ref/SMP/SMPDetail2.html?EGV572.jpg. There is
also an air tube that runs to the catalytic converter that might have a
valve on it that opens / closes on start-up.

> Hi all - car is a 1985 Corolla SR5, 224k miles.
>
[quoted text clipped - 5 lines]
>
> Thanks all

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Masospaghetti - 30 Jun 2006 22:33 GMT

Thanks for the reply.

I didn't think about looking at the different temperature-activated
valves in the car -- I will definitely do so.

There is an air tube that runs from in front of the timing belt down to
the cat.

> Since the leak only happens when the car is first started, both hot and
> cold, it could be the EGR valve or gasket that is leaking. That is one
[quoted text clipped - 14 lines]
>>
>> Thanks all

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HLS@nospam.nix - 03 Jul 2006 19:59 GMT

> Hi all - car is a 1985 Corolla SR5, 224k miles.
>
[quoted text clipped - 3 lines]
> definitely under the hood somewhere. It goes away after a couple of
> minutes of driving.

A length of heater hose, used as a stethiscope, is a very useful tool
sometimes.

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