Catalytic Converter Removal and Replacement

Hi, me and my dad are putting a new Catalytic Converter in our 1987 BMW 535 IS. We’ve managed to get the rear of the Catalytic Converter disconnected from the exhaust, but where it bolts onto the engine is giving us a little trouble.

Any tips on getting it unbolted?

Any help would be greatly appreciated!

We are trying to remove the middle section of the exhaust from the exhaust headers, which are surprisingly short on this car! We don't have air tools - just hand tools and a lot of extensions.

I'm pretty sure these bolts have been in place since the factory installed them in 1986 or 87 depending on the build month. They aren't budging so far.

In a few cases I have ended up giving up and using a sawzall. That is after using an impact gun to completely strip something, or in a few cases, to just break the hardware.

Some of that hardware is just not gonna come apart.

It sounds like you don't have room to cut that section off near the header. I think you should post a photo of the area to help.

Options may be:

• Remove the exhaust manifold and deal with it off the car. Or replace with new manifolds.
• Hack at it with a rotary tool to cut the head of the bolt/nut off.
• Cut as much of the exhaust as you can if that helps get you a better angle to torque the bolts.
• Blast the nut with heat or manifold with heat from a strong torch then see if it comes out. (I have only had success with heat once. Not my favorite)
• PB Blaster

We were able to get it off with patience and a couple soaks of PB Blaster over a couple days. Same thing worked for the oxygen sensor, though we had to use the force of a sledge hammer and a 6 point closed end wrench...

Penetrating oil (FWIW, I was soaking it ~3x/day even if you didn't see me doing that), patience, and a breaker bar...

PB Blaster is pretty impressive.

for the header nuts, that was a 1/2 bar and some long extensions... but some hammering to tighten, then loosen, then tighten, then loosen did eventually break things loose.

For the O2 sensor, I damaged the flats trying with a Harbor Freight O2 sensor socket (it spread open and the sensor stayed right where it was). More PB Blaster, more time, and a 6-point Craftsman wrench (plus the sledgehammer described above) got it done.

Thanks for the advice everyone!!