Separating Exhaust

I'm installing a new catalytic converter soon and am concerned about separating the old cat from the muffler. Cutting it off from the old one is not problem but I'd much rather be able to pull the old cat out of the muffler opening. From those who have gone down this road is this a likely possibility or is it more likely that the 2 are fused together and inseperable? TIA

yardape said:

I'm installing a new catalytic converter soon and am concerned about separating the old cat from the muffler. Cutting it off from the old one is not problem but I'd much rather be able to pull the old cat out of the muffler opening. From those who have gone down this road is this a likely possibility or is it more likely that the 2 are fused together and inseperable? TIA

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Ah what year?

....

Its a '94,.... but the muffler is only 4 years old. The cat is the original with 145,000.

The only way I´ve had any real success is a torch, heating it and seperating it. Remember the exhaust is connected at the exhaust manifold and beating on it most anyplace, is gonna transmit some of that energy to places, you don´t want.

Yes my plan was to first cut the cat off of the down pipe, enabling me ot lower the cat and back a bit to do the rest. That way if I have to hit on it I won't be sending vibrations elsewhere. Thanks. I was also going to presoak with PBBlaster.

From my experiences w/ doing the same thing, it's much easier to just cut it. After wresling with it for close to an hour, I brought out the sawzall and had the whole system apart in 10 minutes.

Cutting it works for me as well but then I have to deal with extracting the output tube of the cat from inside the muffler inlet. That was my second alternative. In theory once its cut I was assuming if I slit the inner tube from the cat that is left inside the muffler inlet, I should then somehow be able to pry and pull it out with a screwdriver and needlenose pliers. Is that what you did?

I had to replace the downpipe anyway (hit a rock or something) so I just grabbed the saw and went to town. Once you have one side off, its easier to grab at the thing and wiggle the other side out. Since the muffler is new, its probably not factory tight and should come out easier than the other side, possibly w/ no cutting needed. I would start by cutting the cat inlet, not cutting the downpipe. After the cat is off, you could try pulling the leftover part of the cat inlet out, by cutting a slit, cutting it into 2 pieces or trying to crush it. Use big pliers. Good idea someone mentioned about disconnecting the downpipe from the header, I would replace the seal between the two while theyre apart.

yardape said:

I'm installing a new catalytic converter soon and am concerned about separating the old cat from the muffler. Cutting it off from the old one is not problem but I'd much rather be able to pull the old cat out of the muffler opening. From those who have gone down this road is this a likely possibility or is it more likely that the 2 are fused together and inseperable? TIA

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I'm guessing that you have bought the new cat already - if you bought an OEM-fit type (has the square flange), perhaps you can tell me: does it come with the gasket and four bolts?

I'm figuring on replacing my cat this summer (214,000 miles, factory-original to my '92), and am figuring that the four bolts that connect the cat to the downpipe are not going to be salveagable, and that it'll take some quality time with the hacksaw to get them off.

Rob

Actually my cat has no flange at the inlet. Its a '94 and the original with 145,000 miles. The Jeep failed emmissions inspection and is getting an O2 sensor as well. The cat slips over the output of the downpipe and is clamped. That side is a no-brainer to get off. The muffler is Rusty's cat-back flowmmaster and is about 4-5 years old. Given the information I have I am confident now that getting the convertor off without a torch will be "relatively" easy and that the whole job will take less than an hour. Thanks

yardape said:

Actually my cat has no flange at the inlet. Its a '94 and the original with 145,000 miles. The Jeep failed emmissions inspection and is getting an O2 sensor as well. The cat slips over the output of the downpipe and is clamped. That side is a no-brainer to get off. The muffler is Rusty's cat-back flowmmaster and is about 4-5 years old. Given the information I have I am confident now that getting the convertor off without a torch will be "relatively" easy and that the whole job will take less than an hour. Thanks

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Interesting - I would have figured that any HO in the 91-96 range would have used the same fittings. Then again, we are talking about Jeeps here...

My '92 has a square flange at the bottom of the downpipe, and the cat has a matching one. There's also a little hanger bracket there, and it appears to use one of the bolts on the flange as a mounting point to support the cat/downpipe.

In my case, I passed emissions the last time (last Dec), but the HC reading was close to the upper limit. I looked at it about 3 months ago, and noticed that I could separate the outer shell by hand, as the seam on the driver's side seemed to be rusted into nothingness. Additionally, I noticed a lot of heat buildup on the shifters inside the cabin while on the trail at NACFest, which did not manifest when cruising on the roads. I'm guessing from this means that either the heat shield is toast (more than likely, given that it's the original one), or it's starting to plug and generate excess heat that is overwhelming it's current dissipative capacity at very low speeds. The latter theory would be supported by the fact that it sometimes feels as if it is laboring a slight bit to accelerate on upward grades on the highway.

Knowing my luck, I won't get to it until next month, as I have a non-functional starter motor on my old Dodge to fix this month so I can attempt to get it inspected (oh fun, emissions-testing a 21-year-old carb'd engine with stale gas in the tank)