My 98 Dodge Dakota has started to have some significant rattling.
When I got under the truck to inspect, it seems that the exhaust
system is rattling. The mounts and clamps are all fine but when I
knock on both the muffler and the catalytic converter they rattle like
something has broken loose internally.

Other than being very irritating is there any problem with ignoring
this. Not getting an sensor signals and don't seem to be getting any
back pressure power loss.

You betcha.. eventually the "cat" is going to plug up and blow your head
gasket, egr and probably burn up some other things.. I would fix it if I
was going to keep the car.

If you are not in a I/M area I would probably punch or gut the cat. The
muffler is not going to plug so badly it will damage anything but the
cat theoretically might.

If you can get away with doing it getting rid of the cat and changing
out the muff would be optimal.

On Mon, 19 Sep 2005, Frank Boettcher wrote:

Fairly typical failure mode for both mufflers (baffles come unwelded) and
catcons (biscuits degrade, shift and rattle). It's entirely possible that
only one component or the other has failed internally -- the suspension of
the exhaust system is such that knocking the muffler causes the catcon to
vibrate as well, and vice versa.

The idiot who suggested gutting or removing the catalyst is, well, an
idiot. It won't help your car run better or more economically compared to
a properly-functioning catalyst, it will cause your "Check Engine" light
to stay on constantly, it *is* Federally illegal, and it will turn your
SUV into a gross polluter.

Just replace my muffler locally but bought my cat from
http://www.performance-curve.com/ could not beat the price and free
shipping. mine was a 99 Ram and the honeycomb was in pieces when I cut off
the old cat and looked inside. I forgot just how quiet the truck was even
with the flowmaster muffler!
-Jerry
"Frank Boettcher" <fboettcher (AT) comcast (DOT) net> wrote

me! wrote:

If a clogged cat can "blow the head gasket" on a 98 Dakota (which would
have either a 5.9 or 5.2) I'll EAT the blown gasket. All the engines
available in the Dak that year were iron head/iron block designs with
pretty much indestructable head gaskets (short of running the enigne
with no coolant whatsoever).

But yes, a rattling ctalyst can eventually shatter the matrix in the
catalyst and restrict the exhaust, which will KILL both power and
economy. But it won't blow a gasket on a 5.9 or 5.2!

If you don't have a post-catalyst sensor the engine will never even
know. If you do you will need to make firmware changes or come up with
a gizmo that provides the "expected" input to the ecu. Probably doable
with a couple of dollars worth of parts-either resistors or a tiny DC
supply.

Decatalyzing cars is environmentally beneficial if you are not in a
major metropolitan area like LA. HC and CO will break down to CO2
whether in the converter or the air. NOx will be slightly more trouble
but it too is primarily a smog zone area.

Plus cars SMELL so much better with no catcon....if it didn't have an
O2 sensor I'd say throw a tank of 100LL in occasionally just for the
good smell.

On Tue, 20 Sep 2005, Bret Ludwig wrote:

But, his Dak being a '98, he *does* have both upstream and downstream O2
sensors.

Horseshit.

On Tue, 20 Sep 2005 23:53:43 -0400, "Daniel J. Stern"
<dastern (AT) 127 (DOT) 0.0.1> wrote:

Sure do,downstream is right behind the catcon


Hey I'm not planning to decatalyze this vehicle. I've been busy
running back and forth to the MS coast helping relatives clean up and
cope. I don't have time to fool with this thing right now and I just
need to know if delaying will cause any permenant damage. Seems to me
that I would get an O2 signal if the catylytic converter wasn't
working effectively and some back pressure power loss or roughness
prior to any other major damage from plugging. Right now it is
running smooth as glass and the rattle, while very irritating, is
only significant at idle.

Frank

On Wed, 21 Sep 2005, Frank Boettcher wrote:

No, if it's running properly you're fine. Excessive restriction would
manifest in reduced performance and mileage and easy tendency towards
spark knock. Get it fixed when you have the time.