You camping again Karl? Sheesh by now I would think I would need a cup of joe and be reading what an easy replacement it was 😀

 

I wish! Got other higher priority crises around the house requiring my attention. For example, had to split and stack 2.5 cords of firewood yesterday. You free to swing by and rub my aching back?

 

Swapped out the bad cat this past weekend. Not too bad a job, but a couple of gotchas to consider. Also, I encountered an apparent manufacturing defect where the upstream O2 sensor fits. Be sure to check this before installation, more details below.

Tools required:

15mm deepwell socket (headpipe to exhaust manifold)
16mm deepwell socket (converter to muffler clamp)
22mm O2 sensor socket or crowsfoot
Exhaust pipe stretcher kit (may not be required)

Jacking up the car for access underneath the middle is something of a pain. Specifically, at the rear jack points (just forward of the rear wheels), there's not enough room to position a jack stand next to the jack. The front jack points (aft of the front wheels) are similar. Rather than lift the car by all four corners, I tipped it to the side. First, I raised the side using a floor jack (with pinch weld adapter) at the front jack point. This raised the whole side high enough to put a jackstand under the rear jack point. I put a second floor jack under the front crossmember, and raised it just enough to unload the first floor jack. I then removed the first floor jack and put a jackstand under the forward jack point. A little unorthodox, but it worked. I left the second floor jack under the front crossmember as a precaution. Whenever you have a vehicle on jackstands, always give it a good shake before crawling underneath.

The front of the converter assembly (converter plus pipes) is secured to the exhaust manifold by a flange and two nuts. The manifold has two protruding studs. One of these nuts fought me, but I got it loose eventually. I recommend replacing the original steel nuts with brass. The threads are M10-1.5.

The rear of the converter assembly fits inside the pipe to the muffler. A wide band clamp secures the joint. I had to expand the muffler inlet pipe slightly to get the converter to fit. On the new converter, the end of the pipe had a pronounced burr, so take a few minutes to file this off for an easier fit. When installing the new converter, wiggle it a little to help the pipes mate together. The muffler is on flexible mounts, so pull it forward for a good fit while seating the converter. I tapped the pipes with a soft mallet to help them telescope together.

Here are the new and old assemblies side by side. The old converter had obviously been replaced at some point and was probably not stock:




I was pleasantly surprised how well the new converter fit. The bends were right on the money, and the unit tucked up well under the chassis.Make sure to apply anti-seize compound to the three fasteners. On my '02 V6, clearance with the oil filter was tight during removal and installation, but it still worked. In a pinch, you could always remove the filter for another couple of inches clearance.

Here's the only problem I had. I was upset that the product shipped with this obvious defect, and was doubly upset with myself for not catching it before installation. I had the new converter installed and thought all I had left was to reinstall the O2 sensors. I was busy patting myself on the back, which is not easy to do while laying on a creeper. The downstream sensor was easy enough, but the upstream sensor would not fit. I was working blind, and thought maybe the threads were damaged. I chased the threads with a tap, but still no joy. Peeking in the open hole with a mirror, I could see the hole was partially blocked. The converter had to come back out again for further investigation.

Here's what I found. In this picture, I'm shining a flashlight in the inlet pipe, where it attaches to the exhaust manifold. Look at the hole for the sensor in the middle of the picture. The light tan color seen in half of the hole is the converter substrate. The dark color in the other half? That's the inlet pipe extending too far and blocking the sensor from being installed. I had to cut away the offending material with a die grinder, and then the sensor fit just fine.




Other than the manufacturing defect blocking the sensor from fitting, this seems like a good product. I could have been done in approximately 3 hours, but the rework added about 1 more hour.

The only other gripe I had was the downstream sensor was in a slightly different spot, and didn't leave much slack for the wiring. I had to bend the connector bracket to provide a little extra play.

 

Excellent write up as per my expectations from you. After you drive some miles maybe you could take an upstream o2 reading on both sides and post if any usable info. I am going to do both mine in october. Maybe all o2 sensors would be better. Your call

 

Man that pipe blockage woulda pissed me off. Wicked pissed as they say back home. I recal lhaving to file off the pipe burr at the muffler end too. And there was a bump in the flange end from the pipe weld that needed filing to get a good snug fit at the manifold.

I think the biggest problem is that these aftermarket cats are just not as good as the stock originals. Let me know if you throw any 0420 or 0430 codes.

Oh and I just remembered there was a specific break in you need to do. S
did your pipes come with those instructions?

 

Two weeks and 500 miles later:

All good. The code has not returned.

I plan to do the other side in the fall, mostly because I can't stand knowing the two cats are different...

 

Good.

Probably best to leave it alone but check OBD trims etc.

 

Finally got a round Tuit and replaced the other cat:


Figured out a little trick to help assemble the slip joint between the cat outlet and muffler inlet. First, make sure you deburr the end of the new pipe. Most likely you'll need to use a pipe expander on the muffer inlet. The expander worked much better with an impact gun versus a wrench or socket. But to remove the expander, don't use an impact gun. It unthreaded so fast, and spit the guts out of the expander and into the muffler inlet. I had to use a magnet on a stick to retrieve the piece. If you unthread it slowly with a wrench or socket, you won't have that problem.

Pulling the slip joint together is probably the hardest part of the job. This time, I used a ratcheting tie down strap, like used on a motorcycle trailer. You'll want one with a narrow strap, maybe an inch wide, so the hooks are fairly small. I hooked one end into the hole for the downstream O2 sensor. The other end was hooked over the short welded bar between the two muffler pipes. Get the slip joint started and tighten up the ratchet. Tap the slip joint with a mallet. The strap applies some pressure while the tapping action sets up a vibration. Tighten the ratchet some more and repeat. Each time I got a small fraction of an inch, but after about a half dozen bites, the slip joint was properly assembled.

This image shows the muffler assembly, with an arrow pointing to the location to connect the ratchet strap: