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95 Legacy EJ22 5MT, 98 Legacy EJ22 5MT, 99 Legacy Outback EJ25 4EAT "Agent 99", 01 Forester EJ25 4EAT
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Discussion Starter #1
I've done this once before - trying to unscrew an oxygen sensor from a catalytic converter and have the bung (threaded female) fitting break off the cat instead. I'd like not to do it this time. What's the trick?
 

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I simply cannot abide useless people.
2006 2.5i and 2002 3.0 wagons.
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Aerokroil
PB Blaster
DIY 50/50 ratio of ATF and Acetone

Soak a lot. Cross fingers.
 

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03 H6 OBW & 06 WRX Sportwagon
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^^ spray penetrant when it's hot - might pull some into the threads as it cools.

also, try to work on it while it is warm. TRy turning a little in the tighten direction too. work it back and forth.
 

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I don't think there is a secret. Just luck. I always make sure I have pre-soaked the heck out of it with PB Blaster, have the right socket and the welder nearby just is case my luck runs out.
 
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Reactions: 1 Lucky Texan

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Master Caster
2005 XT, Mildly Modified...2006 XT Limited, Highly Modifed
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Pre-soaking, as said is the key. Not just hitting it at the time of the work. Pre-soaking means...saturating it 1/2 a dozen times or more over a few days to a week. Actually give the stuff time to creep in.

I have also had greater success on stubborn bolts by shocking them. A impact wrench works of several reasons. I will strike either the drop box wrench or the ratchet with a hammer when I loosen stubborn threads by hand. A few increasing effort taps and the shocking action of the strike will often break things loose.

The same effort made with a cheater bar has the potential to twist and break the bolt. (or sensor/bung in this case)
 

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2002 Pair: 3.0 VDC Wag & 2.5 Limited Sedan
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^^ spray penetrant when it's hot - might pull some into the threads as it cools.

also, try to work on it while it is warm. TRy turning a little in the tighten direction too. work it back and forth.
to augment what has already been said:


haven't seen it in person, but have heard of it,

with the larger part (in this case the exhaust) hot, (be it from running or maybe with a little help from a torch on mild)

then take a gel cold ice pack to the part that you want to remove. and hold it to the smaller part (in this case the sensor).

such might shrink the smaller item away from the larger item at least enough to get some more penetrating oil in.
 

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Master Caster
2005 XT, Mildly Modified...2006 XT Limited, Highly Modifed
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@1 Lucky Texan. "Big Bang" ...way to double down on that one.

Simply put...put a wrench on it and hit it with a hammer.

Which has been a pretty decent mantra for me for most of my life. Most of the time whatever I do involve turning itwith a wrench, or hitting itwith a hammer. Sometimes...both.
@eagleeye. Cycling a few times with MAP gas can be a big help. Shocking the threads during the heating and cooling process helps as well.
 

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95 Legacy EJ22 5MT, 98 Legacy EJ22 5MT, 99 Legacy Outback EJ25 4EAT "Agent 99", 01 Forester EJ25 4EAT
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Discussion Starter #11
The Feynman van was a really sweet touch.

I didn't have any of the above on hand, so I gave it a few shots of (the admittedly inferior) WD-40, got a wrench on it, and then tapped on the wrench with a hammer, back and forth, for about 15 minutes, spraying as I went. Then a prayer and a tug broke it free where it shoulda.
 

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1999 30th Anniversary Legacy Outback DOHC 2.5L 4EAT, 2008 Impreza WRX 2.5L 5MT, 2008 Impreza Wagon 2.5L 4EAT
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The Feynman van was a really sweet touch.

I didn't have any of the above on hand, so I gave it a few shots of (the admittedly inferior) WD-40, got a wrench on it, and then tapped on the wrench with a hammer, back and forth, for about 15 minutes, spraying as I went. Then a prayer and a tug broke it free where it shoulda.
The main thing is to lubricate the threads as you unscrew the sensor. The ones I have removed have all been somewhat tight so continuing to spray lubricant on the threads helped get mine out.

Glad you got it out ok.
 

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95 Legacy EJ22 5MT, 98 Legacy EJ22 5MT, 99 Legacy Outback EJ25 4EAT "Agent 99", 01 Forester EJ25 4EAT
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Discussion Starter #13
And from what I could see from searching around, copper antiseize is the right thing to use with the new sensor (that was an econo from Rock that didn't include any).
 

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Master Caster
2005 XT, Mildly Modified...2006 XT Limited, Highly Modifed
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sensors...good one usually have an anti-seize applied by the sensor mfg.
 

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And from what I could see from searching around, copper antiseize is the right thing to use with the new sensor (that was an econo from Rock that didn't include any).
last one I bought was a denso and it had a small finger sized envelope of copper in the box.
 

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Master Caster
2005 XT, Mildly Modified...2006 XT Limited, Highly Modifed
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last one I bought was a denso and it had a small finger sized envelope of copper in the box.
The last 2 O2 sensors I handle were both Bosch and had a dry material already applied. Similar to air fittings you buy at Hope Depot
 

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2002 Pair: 3.0 VDC Wag & 2.5 Limited Sedan
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The last 2 O2 sensors I handle were both Bosch and had a dry material already applied. Similar to air fittings you buy at Hope Depot
and the last beer I had was a miller high life. that someone gave me for moving a mattress / box spring.....and I still don't know what would possess someone to buy any of that boring stuff. :23:

grey dry material like powderd graffite or dry lithium white grease.
 
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