Oxygen sensor removal - engine hot or cold?

[BASL2]

I need to remove the old front oxygen sensor on my 1996 SL2. Should the engine be hot, warm or cold in order to make removal easier? I tried a bit with the engine cold, but didn't want to force it for fear of breaking something. Thanks!

[92SC2]

COLD! You'll likely burn the snot out of yourself if you do it hot. If you can squirt it with PB Blaster one evening and pull it out the next morning/day. That will give the PB Blaster a chance to creep in and loosen things up a bit.

[richpin06]

Originally Posted by BASL2

I need to remove the old front oxygen sensor on my 1996 SL2. Should the engine be hot, warm or cold in order to make removal easier? I tried a bit with the engine cold, but didn't want to force it for fear of breaking something. Thanks!

Warming up the cold engine for 2 minutes expands the manifold a little to help in removal.

http://www.youtube.com/watch?v=ttUHqVz-sL0

[92SC2]

Originally Posted by richpin06

Warming up the cold engine for 2 minutes expands the manifold a little to help in removal.

http://www.youtube.com/watch?v=ttUHqVz-sL0

Which will most likely end up tightening the manifold on the sensor. It's not like freezing a wheel bearing and heating the race or freezing a 10/22 bbl and heating the receiver. If you fire up the car you're heating both the O2 sensor and the manifold causing both to expand.

[madpogue]

Which one expands more depends on the coefficient of expansion of the two materials (the thread base of the sensor and the manifold).

[Signmaster]

If the sensor expands quicker with heat, it should also cool quicker when the engine is turned off.

Sounds to me like a good argument towards heating the engine some first.



I've never had to pull one on the Satty yet, but most of the time exhaust sensors have come out better when the engine is warmed first.

[92SC2]

Have fun heating your manifolds to remove your O2 sensors. If you insist on heating them first spray with a penetrating oil so it will be drawn into the threads. Caveat emptor, wear your waders.

[1999greenSL2]

From a different perspective here, just give it all you've got. You're not going to break anything.

[amazinghl]

I only remove o2 when it is cold. Use the correct size wrench and PB blaster.

[TwinRevver]

crescent wrench with cheater bar and warm motor will do it. Just did on today

[denisond3]

The penetrating oil is a good idea - especially if you can spray it on twice a day for a few days - without driving the car in the meantime. That just vaporizesd the penetrating oil.
Try hitting the O2 sensor on its side a few times, close to where it threads into the manifold. This will help to shock the threads loose. Use a 6 point wrench when you are trying to turn it - not a 12 point. They make deep sockets that have a notch cut out of them, so it will go down over the wires. I would estimate it might take 100 -120 lb-ft of torque to get the thing to unscrew. It should only be tightened up about as much as a spark plug - maybe 20 lbs-ft.
If you run the engine to get thing warm, you could then dribble water on the O2 sensor just before you try to unscrew it.
The ultimate technique is to heat the manifold 'bung' with an oxy-acetylene torch, to expand the threads on the manifold. This usually requires removal of the radiator fan, to have clearance for the torch and its 4000° flame.

[wolfman]

One word for ya....and its not COLD
Or HOT
But WARM.

As in run the engine for 1~2 minutes (from a cold start) The Manifold will heat faster than the sensor expanding ever so slightly around it, making the sensor easier to remove.

[geartooth94]

nah don't worry about changing it hot. the manifold only gets up to like 100 degrees with the engine on!

[1999greenSL2]

Honestly, it can be done with hand tools without days of soaking in PB blaster. Just force it. Mechanics don't have all that time to fool around, so thats their only option.

[92SC2]

Originally Posted by geartooth94

nah don't worry about changing it hot. the manifold only gets up to like 100 degrees with the engine on!

Are you talking about the exhaust manifold or degrees celsius?

[madpogue]

Originally Posted by 1999greenSL2

Honestly, it can be done with hand tools without days of soaking in PB blaster. Just force it. Mechanics don't have all that time to fool around, so thats their only option.

Mechanics have the option of breaking off (or rounding off) the sensor, replacing the manifold and charging the customer. DIYers have that option, too, of course, but they're not spending somebody else's money.

Originally Posted by 92SC2

Are you talking about the exhaust manifold or degrees celsius?

I think s/he was joking...

[1999greenSL2]

Originally Posted by madpogue

Mechanics have the option of breaking off (or rounding off) the sensor, replacing the manifold and charging the customer. DIYers have that option, too, of course, but they're not spending somebody else's money.

I think s/he was joking...

I think dirty shops like you're describing are much more rare than the stories about them. I can't even imagine that happening where I work. Shops have to sell jobs. Not just get the car, do whatever the hell they want and give it back to you with an invoice. Get the car, diagnose it, call customer to sell the job... anything that goes wrong - like needing a new manifold after trying to replace the o2 sensor - would have to be paid for by the shop.

[madpogue]

I'm not saying that they would intentionally, or even negligently, break the sensor. I'm just saying that, even with the best of intentions and the most careful preparation, if a mechanic breaks a part off in another part, the customer pays to replace it. That's not "dirty", that's just the breaks. How many times has a $20 brake bleed job turned into a $100 bill for a new wheel cylinder, that was perfectly serviceable until the mechanic, doing her/his level best, breaks the bleeder off? When you're spending your own money, you're less likely to simply follow the step-by-step instructions, and more likely to try an extra step or two to avoid breaking, or rounding, or otherwise damaging something.

[L100andSW2]

Originally Posted by amazinghl

I only remove o2 when it is cold. Use the correct size wrench and PB blaster.

This way worked for me. Plus it seemed a little reluctant after the sensor first loosened so again sprayed PB where the threads meet the manifold, worked it back and forth a bit and then did a nice clean wrench turn to the left. Another short PB spray...reposition the wrench...work it...turn. Didn't want to break anything, but slow and steady will do it.

[eljefino]

Not a fan of all this PB blaster advice.

I've used it on the manifold studs which are little and brittle and need all the help they can get.

The o2 sensor has anti-sieze on it and seems to be of a sturdy enough stainless-type metal. Plus it's BIGGER than the outer diameter of a lugnut!

Throw a foot long open end wrench on it, or disconnect the wire and feed a box end wrench over it if you're paranoid.

Tap the other end of the wrench counterclockwise with a sledgehammer. Start with small taps.

So why am I not a fan of liberally soaking the exhaust manifold in PB blaster? The smell and the smoke! You'll think your car is on fire the first time you do this.

Might as well put some MMO down your spark plug holes at the same time, so you can fog for mosquitoes from the front and the rear all at once!