Oxygen Sensor - Now What ?
 

Typical one step forward and two steps backwards on what should have been a simple repair - the Oxygen Sensor on my 84 928 is not only dead but rust welded in place.

I thought the next step would be to simply remove the catalytic converter assembly up to the exhaust manifolds. No luck - all four bolts at the cat end and the bolts at both exhaust manifolds were solidly rusted in place. Everything rounded off even after several days of soaking in penetrating oil and alternately applying heat. OK - just used a cutting torch to lop off each nut but now it looks like the remainder of the bolts are threaded into all three couplers. A center punch doesn't seem to budge a thing. Are the factory assembly bolts really threaded through the connectors with the nuts used for a backup !

I haven't done any real damage yet but Please Help - short of dynamite what is next ?

UPDATE - Thanks for the advice and comments – I will take a run at it again tomorrow afternoon. Even with the nut end of the bolts cut off, they sure did seem solid. Stand-by for news - Well after burning off the nut end and bolt heads at every connector - success at last. I had to finally drill out three of the toughest bolts that did not respond well to a punch and large hammer. Now to break loose the oxygen sensor that is similarly rusted in place. Dynamite is currently on hold for now -
Thanks, Michael

The stock iron manifold just has holes for bolts to go through, but no telling how the head pipe might be done.

Which penetrating oil did you try?

I helped a local guy remove his on a 83 model just a couple weeks ago. No threads. Just burned the nut off and they fell out.

Yeah, I agree with Dean. I have had stubborn rusty exhaust bolts and nuts and I just used a Torch from Home Depot (get the yellow bottle, it's hotter) and off they came. Oils and Penetrants can only go so far, then you have to bring out the big guns.