Some GM products have a gasket under the EGR valve, that can blow out.
If your engine has 'pulse' air injection, a bad reed valve can let
exhaust gas leak (although it usually winds up in the intake); and the
tubing sometimes rots through (but that usually makes a noise).
Check around the heat riser valve too. On my 2.8 V6, the riser valve is
held by the same bolts that attach the exhaust pipe. It's easy to knock
the valve loose when changing the pipe.
CO of course is colorless and odorless, what you are smelling is likely
HC of some sort. It may not be exhaust gas, so also look at the PCV
system, carbon cannister, etc. Oil, coolant or ATF dripping onto an
exhaust pipe can also be a good imitation.
Randall
Tim Mullen wrote:
>
> Question about sources of an exhaust leak.
>
> My son's '85 El Camino (305 V8, 4 bbl) appears to have an exhaust
> leak, but it's not coming from the exhaust pipes. It has a new exhaust,
> from the manifolds back (including the cat), but there appears to be
> a small leak. There is not noise, no air (exhaust) "puffing" out of
> manifold joints, etc. but there seems to be the smell of CO around
> the vicinity of the engine (and unfortunately into the cowl vents to
> the interior.
>
> Any suggestions as to what could be the cause? I'm thinking that
> it might be the EGR valve, but I've never heard of one leaking, just
> not working... Any body??
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