Advice for stripped threads upstream oxygen sensor exhaust manifold

[Arlen Holder]

Car is just bought by a kid just learning to drive (he's 16).

2004 Mitsubishi Lancer ES

Neighbors asked me to teach him how to replace the oxygen sensor (due to emissions code).

The threads were stripped and "filled" with some kind of hardened "metal paste".

The new part is a Denso 234-4739 (marked 485000-4060, 07U05) The old part is a Denso (marked 234000, 8643, 07E23)

What would you suggest?

- Tap the threads? (22mm hex nut)

- New exhaust manifold?

[fozz89]

replying to Arlen Holder, fozz89 wrote: You could try and tap. (cant see your pictures BTW) It depends on how much material is missing from the original threads. I dont know my way around Jap cars too well but usually with the right equipment you can just flash the PCM and make emissions BS go away permanently (along with your catalytic converter) More HPs, Better mileage, more crying liberals.

[Paul in Houston TX]

IF it were my car and IF the manifold is steel, I would remove the manifold, then remove the square nut, and weld or braze in a thin-ish nut of appropriate thread size. If no thin-ish nut is available then make one with the dremel. The sensor needs to be in the flame and also have good thermal conductivity to the manifold.

[rbowman]

Back to your friendly Loctite dealer for the Form-A-Thread kit? Trip to a junkyard for a new manifold if replacing it isn't too painful? Helicoils?

[Arlen Holder]

I had not thought of putting a new nut on. I'll look in the morning to see if the nut is the only threads. I'm sure the sensor has to be "in" the stream of hot vapors.

It seems to be cast iron. Aren't they all that way? (It's rusty.)

[Arlen Holder]

I guess it can't hurt. I can contact Denso to figure out the thread pitch for their O2 sensors.

I was thinking of cleaning up the threads, but they look really bad. How on earth can ANYONE do that to a bunch of threads?

What did they do? It's not even hard to get to ... it's right there ... in front.

[Arlen Holder]

Seems to me the choices are... a. New or used manifold (if it's not too hard to replace) b. Drill it out and helicoil it (nothing to lose really) c. Clean it up with a tap (I don't have the tap, which won't be cheap) d. Shove it in there with epoxy (I hate that idea so I don't want to)

[Arlen Holder]

Thanks for confirming it's the same threads as a spark plug, which, at the moment, seem to be 18x1.5 for them.

Googling, it seems cast iron isn't easy to weld, and that the plug rethread might work, but, the heat cycling has likely hardened the bung nut, such that it's a LOT harder (some say) to deal with than a spark plug thread which is typically in aluminum engine blocks (they say).

Searching for this "plug rethread kit", is this the $62 kit you speak of?

[rbowman]

The helicoil route won't be cheap either. The epoxy route is redneck engineering at its finest but this is a 14 year old beater, right?

As an aside, general purpose epoxy isn't a good idea for an exhaust manifold.

[trader_4]

I'm a conservative and I don't think it's a good idea to modify cars so they pollute either. Amazing that someone could turn a simple repair into that nonsense. Also, with the emissions BS going away permanently, I wouldn't be surprised to see it have lower mileage too, because the computer winds up running it open loop, guessing at what's going on, instead of running it closed loop.

[Arlen Holder]

There's a reason I didn't respond to that suggestion of removing emissions. There is absolutely zero chance we are going to mess with the emissions. Zero.

It's going to be street legal smogable or we won't do it.

[Scott Dorsey]

You have it out, measure the pitch. The helicoil is probably the easiest solution and I am generally a fan of the things.

They tried to remove a stuck oxygen sensor cold, maybe without even using a proper penetrating oil, and they just put force on it until it deformed and eventually tore itself out.

Are you absolutely sure it's the problem also?

--scott

[Arlen Holder]

From research since yesterday, all oxygen sensors seem to be M18x1.5 so I'm clear on that.

Thanks. I think my current plan is: a. Pick up a thread chaser & try that b. If that can'd be found, consider a junkyard exhaust manifold c. If that fails, consider a new one d. If that's too pricey, consider a helicoil kit (but they're pricey too) e. Maybe even consider drilling and then inserting a threaded bung

Jesus. Who would do that. I have never stripped a thread coming out! (I've stripped threads going in, but never coming out.)

It is now. :)

[Steve W.]

Plug threads are M18 x 1.5 or M14 x 1.25 on most automobiles. The M18 are the older plugs and O2 sensors and the M14 are the common peanut plugs used these days.

Heat cycling will have made the iron harder to work with but the tools used are designed to handle that.

That kit would work but I like using a solid insert myself, they hold up better. I use timesert myself.

If you check with many of the chain parts stores they may have a thread repair kit as a "loaner tool". You "rent" the tool use it, return it in good shape and get your money back. You pay for the insert(s) you use. A lot cheaper than buying the kit for a one time repair.

[trader_4]

I would not be too keen on that. To swap it you have more nuts, studs, bolts to screw around with and more potential for something else to snap, strip, refuse to come off, etc.

[Clare Snyder]

First of all, it does NOT appear the threads in the manifold are stripped or damaged - but some ham-fist crossthreaded the sensor, stripping the threads off of it, then tried to "glue" it back in.

Get a tap to fit the threads and chace all the crap out of the threads. BE CAREFULL to get it in SQUARE and not to recut the threads in the manifold. After chasing out the threads you should have, if not a full thread, at least enough thread to hold the new sensor firmly in place.

If, by some chance you find the thead IS too badly damaged, now is the time to find out how heli-coils or Speed-serts work. These are thread repair devices that involve retapping the hole to a larger size with a specialized tap, then installing an insert into the hole to restore the thread to the original size and form.

It's a handy process to learn. - but requires some rather pricey tools that you may never need to use again - - - so would likely be "smarter" to have an expert (read that as someone who has the required tools and has done it before) do the job for you.

The tap required to chase out the thread will be metric - usually an

18mm spark plug tap. (or thread chaser)

[trader_4]

I wonder if Advance Auto lends the tools out. They lend lots of tools, no charge. I think Auto Zone might too.

[Clare Snyder]

Defionietly the first step - and extremely likely to work

Likely lots of Mitso-Shitty manifolds in ther scrap heap - but possibly with the same problem -----

Throwing cubic dollars at the problem???

Not if you get someone who has the tools do the job for you. Less than $50, almost guaranteed

Basically a "timesert" - More expensive tooling

You haven't removed many O2 sensors - - - Or Ford Triton spark plugs - - - - - - - - - -

With no good ground through the repair paste, good chance the sensor would not work - and at this point there is NO OPTION - the sensor is FUBAR

[Clare Snyder]

First step is clean out the existing threads - do NOT use a form-a thread type product - needs to withstand high temperature AND be electrically conductive. (some sensors don't need the ground, but many do)

[Clare Snyder]

It's a spark plug thread. I bougrt a thread chaser that does 14 and

18mm threads for under $10 Canadian.

Better yet, pick up an 18mm X 1.5 tap from a local tool supplier - Hanson (Irwin) 2459 is about $12.95 List -

About $36 from Fastenall

Even hOME dESPOT CAN GET IT FOR YOU - PART NUMBER dwtb18x1.5 - $21.14

Don't even THINK about it!!!