Replacing O2 sensor, found rusted threads in turbo

[dkellis]

Hi,
I need to replace the O2 sensor (paperclip technique and ElanScan agree that the sensor is stuck on) and have obtained the OEM part from Dave Bean Engineering. The old sensor came out with some difficulty (hint: run the engine a few minutes to let the housing start to warm up) and was indeed thoroughly crusted over at the business end.
But the new one won't thread in: the threads in the housing are very crusted with rust and the new sensor can't get started.
So what to do now, short of buying a replacement turbo?
Would it be feasible to tap the threads in the housing to ream out the rust?
With the turbo in place on the engine? The shavings and dust would go down the exhaust but would that be harmful to the catalytic converter or other parts? I imagine that a lot of it would just blow out when the engine was started.
I appreciate any advice you all have to offer.
Thanks,
Dave
Redwood City, CA

[F1 LOTUS]

First thing would be to check that the new thread matches the old one by meshing them together and holding them up to a light to see the threads fit each other?

Running a tap down to clean the threads out should not be a problem as you'd only be removing surface rust A bit of grease on the tap will hold most of the debris anyway

[PaulN]

What was the problems you were having with the O2 sensor faulty?

Cheers

PaulN

[stevo]

the o2 housing is part of the downpipe not the turbo. if the thread wont recut then i can supply you a stiffy(uprated downpipe) with a new o2 housing.

[dkellis]

PaulN,
I'm diagnosing a misfire and both the CEL code and ElanScan indicate that the O2 sensor constantly indicates rich exhaust. I'm replacing the sensor to rule it out as a cause of the misfire. I can't pin any symptoms directly to the sensor itself.
-Dave

What was the problems you were having with the O2 sensor faulty?

Cheers

PaulN

[dkellis]

stevo,
Thanks. I'll keep this in mind.
-Dave

the o2 housing is part of the downpipe not the turbo. if the thread wont recut then i can supply you a stiffy(uprated downpipe) with a new o2 housing.

[DeeAitch]

Assuming Stevo didn't get any complaints on 'Project Stiffy' the thread is M18 x 1.5. Not an easy tap to get hold of although sensor threads are pretty much common so any exhaust place should have one. Be careful with swarf - grease is a good idea - I've seen the results of weld spatter on a Cat and it aint a pretty sight. The 'holes' in the cat brick are quite small so any debris bigger than this swirles around and around and wears a bluddy great big cavity in the brick

[Doug]

clear the CEL codes after putting in the new O2 sensor (disconnect battery for a minute) to be sure the CEL goes away. ElanScan can help seeing the O2 sensor readings and other sensors. Yes, a 15 year old O2 sensor will be bad, so replacing it is a good idea no matter what. If a few rust pieces get in the pipe there's not much you can do but at least it is in the exhaust pipe and not the intake pipe

[Enright]

Is there a reason why you suggest disconnecting the battery?

It's just that I hate having to poke about under there, bumping my head on the roof AND stowage cover, getting grease on my hands, and having to re-program the code and all the settings back into the radio.

Doesn't pulling the two multiplugs out of the ECU fulfill exactly the same purpose without any of the grief?

[Ashaman]

You should always disconnect the battery before disconnecting the ECU.

[Doug]

also you don't want to mess up the multiplugs and get some bad connection from it and then you have a whole new problem.

my radio has a battery back-up for those things

[Doc Fizzix]

You should always disconnect the battery before disconnecting the ECU.

EXTREAMELY IMPORTANT TO FOLLOW THIS ADVICE OR YOU COULD SCREW-UP THE ECU

[Enright]

Point(s) taken - thank you for the clarification.

[Sy V]

Oh now they tell me after ~15 removals and re-chips!

[dkellis]

Here's the followup to my adventure with the O2 sensor.

Thanks to Lotusgirlmarie I found a tool and parts shop in Daly City, CA, called Tool Mart, on Mission Blvd, that had the tools I needed. Indeed, I could choose between a metric 18 x 1.5 "Thread Chaser" packaged for O2 Sensors (ie, an application-specific tap), or a metric tap, although they were temporarily out of the tap. I also got an 18 x 1.5 die to dress the threads on the new O2 sensor that I had flattended on a previous try.

So I tried the thread chaser and dang, if I couldn't get it started either; the threads in the manifold are hard enough to flatten the thread-chaser threads. Nothing left to do but carefully thread in the old O2 sensor and then try the new one. This try worked and I carefully seated the sensor and I was done.