Broke O2 Sensor threads in crossover

[sdg3205]

I've got 38,000 miles on my car and had been meaning to change the original oxygen sensor for a year or two. The lambda system was running open loop and super rich when I acquired the car. The culprit was simply a backed out relay pin, but this wouldn't have been kind to the O2 sensor. Once the lambda system was up and running it was very hard to dial in the mixture.

Past removal attempts with various solvents have been fruitless. Today I got out the torch, heated it up and after about 20 minutes "got it loose," except it was so seized it took the crossover pipe threads with it. I now have a gaping hole where my sensor used to be.

Knowing there were used crossover pipes floating around I figured I could just replace it on the cheap. Well, attempts at removing the cat nuts yielded the same result. It makes sense that one seized nut will typically mean all surrounding nuts and bolts exposed to the same elements will meet the same fate.

I'm fairly certain my exhaust system will not be removed without casualties elsewhere even with the usual precautions.

It might be time for an upgrade.

[Bitsyncmaster]

You will have to break off the clamps and maybe a few bolts to get the CAT off. Once things are out in open you can weld on a fix for the sensor. Broken bolts are also easy when thing are in the open.

[Delorean Industries]

I may have a used "good" cross over tube around here. Also stainless options.

[opethmike]

Perfect time to get a Spec 1.....

[vps3922]

Perfect time to get a Spec 1.....

I agree!

But it is kind of a high investment. Unfortunately.

[sdg3205]

Volker - I double checked the icbc repair policies for collector status vehicles and you are right, we can upgrade from cast iron to stainless steel. I know Josh's systems are all stainless (from stainless works iirc).

Until then I'm going to try some high heat JB weld epoxy and jam the old oxygen sensor back in place. I'm guessing driving with that hole wide open would be loud and could damage the epoxy on the frame.

[David T]

Volker - I double checked the icbc repair policies for collector status vehicles and you are right, we can upgrade from cast iron to stainless steel. I know Josh's systems are all stainless (from stainless works iirc).

Until then I'm going to try some high heat JB weld epoxy and jam the old oxygen sensor back in place. I'm guessing driving with that hole wide open would be loud and could damage the epoxy on the frame.

Epoxy can't take the heat. You can repair it with a thread insert like a Heli-Coil. Most large auto stores sell a kit with the inserts, a tap, and an insertion tool. Use a dab of Never Seize on the threads, just be careful not to get any on the probe. BTW for the O2 sensor to work it must make good contact with the metal pipe to complete the electrical circuit. Epoxy will insulate it from ground.

[sdg3205]

Epoxy can't take the heat. You can repair it with a thread insert like a Heli-Coil. Most large auto stores sell a kit with the inserts, a tap, and an insertion tool. Use a dab of Never Seize on the threads, just be careful not to get any on the probe. BTW for the O2 sensor to work it must make good contact with the metal pipe to complete the electrical circuit. Epoxy will insulate it from ground.

JB Weld "High Heat" claims its specifically meant for exhaust manifolds and exhaust systems. Will it work? It just needs to last a few weeks, I'm not looking at a permanent fix.

[Ron]

Permanent fix- You might try purchasing the shortest spark plug non-fouler you can find (< $5.00), drill out the small hole in the bottom to full size to make room for the sensor, then have it welded or brazed in the existing hole. The threads for the sensor will match (confirm for exact unit).

High temp JB there is asking for it IMHO.

[Mark D]

If you're just looking for a temporary fix and don't care if you further damage the crossover pipe you could just plug the hole and disconnect the oxygen sensor. Are you just looking for a way to prevent the exhaust gas from shooting out and damaging the nearby epoxy/frame?

I'm not sure if running with no O2 sensor will have a negative effect on the catalyitic converter... Running rich for extender periods of time can plug the honeycomb brick inside but if you just need to remove the sensor for a week so you can safely drive it to a shop I don't think it will make much difference.

If you are planning to replace the crossover pipe anyway you could modify it to fit a pipe plug...You'd need access to drill the hole larger you could size it to fit a plug... 1/2" NPT is probably about the right size.