Conclusion: Exhaust leak '00 300M (cause, and remedy)

Over the past few months my 2000 300m developed an exhaust bark that
sounded like it was coming from the front or center of the car, not
the rear.

A visual inspection on a hoist (Midas) indicated that the first
muffler/resonator in the exhaust chain was the problem - it's single
seam running down it's side was starting to open up.

Turns out that wasn't the problem.

The problem was in one of the couplers situated mid-way between the
driver's side cat-convertor and the aformentioned muffler. Something
had given way or failed inside the coupler, resulting in a sloppy
internal fit and lots of play (and a resulting exhaust leak).

Even though the muffler's seam was opening up, there is a second liner
right under it that was still intact.

I took the car to a custom exhaust shop in my city (a place where I
took my '73 Satellite about 10 or 12 years ago to have a
stainless-steel exhaust put in - by the same guy). With the engine
running, he identified the coupler as the culprit. This left-side
coupler is a bitch to work on (the right side is much easier) but he
says it's the left-side that always seem to go on the Chrysler cars.

I had the muffler replaced as well (Magnaflow #12258). The coupler
was replaced with a generic woven/braided stainless-steel component.
The exhaust guy said that that was my only option - short of buying a
new cat-converter from Chrysler (that's the only way to get a new
coupler). And the cat is (according to him) in the neighborhood of
$1000. Regardless if he was right about the price, there was no way I
was going to get a new cat-convertor from Chrysler just to replace the
coupler.

Anyways, the generic coupler, the Magnaflow muffler, and labor
totalled about $375. I think with the new Magnaflow that the car is
now a little quieter than original. The Magnaflow was installed
"backwards" but I don't think it matters.

Also...

Back in Feb 2004 the rear driver's side power door lock/latch failed.
I had it replaced by the dealer. It cost (in US dollars) $105 with
$92 labor. I actually paid $140 CDN for the part.

Within the past few weeks, the rear passenger door lock/latch also
failed. The dealer wanted about $100 for the part (being that the
Canadian and US dollars are at parity, the price is cheaper now vs 4
years ago). I would imagine that the price at a US dealer is more
like $65 or $75.

Instead of buying a new one, I picked one up from an auto wrecker for
$35 (it came from an intrepid, but was an exact match). It's a bit of
a bitch to replace.

So that makes both rear door latch units have failed on me. Since
very very very few things on this car have failed in 8.25 years, I
would venture to guess that the door latch units on the LH cars must
have a high failure rate...

 

I will be replacing at least one of my cats on one of my two Concordes -
different engine (2.7L) in that one but same exhaust setup. The exhaust
valve seals go bad in that engine around 125k miles (I'm one oil change
shy of 200k on it now) and the continual diet of oil thru the exhaust
destroys the cat (I always get an "inefficient cat" code for the last 2
years or so).

I don't recall ever seeing such a failure (that coupler) reported on any
of the three LH car forums I frequent, but perhaps it is one of the
types of things that people have fixed and don't write about on the
forums, or possibly didn't nail it down to the exact problem, though
your exhaust man seems to have seen it before on some Chryslers.

Something like that, though prices on a lot of Chrysler parts have gone
up since the Cerebus transfer. The explanation I got was that a lot of
parts suppliers took the opportunity of the changeover to not renew (or
back out of?) contracts, so some parts became in very short supply while
new sources were obtained, so prices went up for a couple of reasons,
some parts a lot worse than others - some by a factor of between 2 and
3, or were plain not available for a while. I haven't had to buy
anything lately so don't know what the situation is today.

Yes - (judging from the forums) those latches and everything involved
with the windows (regulator motor and the glass-to-regulator-attaching
clips, which are shared with a lot of other Chrysler platforms) break a
lot - it's like there was one very poor designer who was put in charge
of "windows and doors" on the LH's. I have been fairly lucky in that
because on my two LH's, I've only had to replace one latch (also one
window motor, and two glass-to-regulator clips).

Other common failure points that come to mind are the engine cooling
fans - the fan motors do wear out (typically at around 100k). Also, the
positive battery post/terminal area is subject to heavy acid/corrosion
and is a source of a lot of weird hard-to-diagnose electrical symptoms
when the connection starts going intermittent/high resistance. But some
of us on the forums have learned to recognize the symptoms when new
posters post them. Positive jump post clamping sometimes gets loose (no
corrosion) and creates similar problems.

Good parts are needed for the brakes, and an occasional front wheel
bearing replacement is needed.

And the usual Nippon-Denso starter solenoid contact click-click-start
failure.

Bill Putney
(To reply by e-mail, replace the last letter of the alphabet in my
address with the letter 'x')

 

Oh - and replacing a headlight bulb is almost an ordeal compared to many
other cars. Also the headlights get cloudy - apparently inferior
materials and/or coatings used compared to some other cars.

And a unique variation of the 9005/9006 headlight bulb design (straight
base rather than the standard angle design) was used - and unnecessarily
so. The headlight housing design could arbitrarily have been different
to accommodate the regular bulbs (identical element/performance).

Bill Putney
(To reply by e-mail, replace the last letter of the alphabet in my
address with the letter 'x')

 

I love a low-cost alternative solution that works.

By the way, I'm surprised to hear that a Magnaflow is "quieter" than
OEM, but then my experience is with the Magnaflow performance line. I
have a pair of their welded-case mufflers on my '69 R/T, and while I
love them they're not exactly "quiet." I take that back, they ARE quiet
at idle and cruise, but when you stand on it they let out a pretty good
bark. A few weeks ago I was out driving in the country with the top
down, not really getting on it or anything. I pulled up to a stop sign,
and the pickup truck that had been cruising behind me pulled alongside,
and the driver said "man, it warms my heart to hear that big-block
sing!" Then he turned right and I got to hear his 24v Cummins sing a bit....

 

Is he maybe meaning it's quieter than the original setup with the bad
coupler?

Bill Putney
(To reply by e-mail, replace the last letter of the alphabet in my
address with the letter 'x')

 

My first impressions is that the 300m is now slightly quieter than it
was before the problems started with the coupler.

You've got to keep in mind that there are 3 separate, muffler-like
objects in the exhaust path on the 300m (and presumably most or all
chrysler products with the 3.5L engine and LH body).

So while the magnaflow muffler is usually what most modded, altered,
or restored cars will have as their only muffling device, in my case
the Magnaflow 12258 is followed by the stock resonator and then the
stock tail-pipe muffler.

The magnaflow muffler is a 5" x 8" oval, with a body about 18" long.

The original OEM muffler was a 4" x 8" oval, with a body about 16"
long.

The magnaflow is (visually) noticably larger, but there is plenty of
space under the car for it.

The magnaflow was used backwards (2 inputs from the cat convertors, 1
output connected to the long exhaust pipe running to the back end of
the car where it connects to I think the resonator):

http://www.magnaflow.com/02product/shopexd.asp?zone=main&id=6918

These are pictures of what replaced the defective factory OEM coupler
located about 1 foot from the left-side cat-convertor:

http://www.alibaba.com/product-gs/203004879/Exhaust_Flex_Pipe_Interlock_Flex_.html

http://www.alibaba.com/product-free/10645385/Bellows_Exhaust_Connector_For_Automobile.html