What do used O2 sensors look like?

[Jlaa]

Are they supposed to be tan? White?
I replaced my two pre-catalyst oxygen sensors on my sport beetle today. Bosch 13721 from Rock Auto. About $72 each. Torqued to 35 lb-ft. The new sensors came with anti-seize on the threads.



I did this at 60K miles / 26 years old to solve code P1115. Feels gratifying. Got to use my O2 sensor thread chaser tool, my el cheapo-crows-foot wrench to torque, and my fancy shmancy gearwrench 90T stubby 3/8" ratchet.



However, the two old O2 sensors had a coating of white on them, like so:



What does everyone else's old O2 sensors look like? I looked up "white 02 sensor" on Google and one possible culprit is silicone poisoning if a silicone adhesive was used somewhere in the engine. I've never used a silicone based adhesive, although I have no idea what a prior owner used. I wonder if the issue is a too-lean-mixture?

9 months ago I had to replace my MAF because some CEL code popped up that said my MAF was faulty and making the mixture too lean. I cannot remember what the code was exactly, but I remember reading about it and the Motronic adaptation was too far out and couldn't adapt for the excessive leanness .... so I replaced the MAF. After replacing the MAF 9 months ago, the “too lean” CEL code never came back. So ... I wonder if these old O2 sensors indicate the mixture was indeed too lean .... or if they look normal? Thanks.

 

[JC220]

I haven't had white ones before normally a black / Tan colour is what I find

 

[sheward]

+1

 

[gsxr]

Not sure I've seen one with a chalky-white residue like that. Seriously doubt it's related to anti-seize.

Do you use any fuel or oil additives? Does the engine consume any oil?

 

[Jlaa]

Never seen one with a white residue like that. Seriously doubt it's related to anti-seize.

Do you use any fuel or oil additives? Does the engine consume any oil?

I use a bottle of Techron once every few years. The engine does consume oil (like a a half a quart every 3000 miles) which is normal for an air cooled sport beetle.

 

[nocfn]

Let us remember you are in the comrade repulik of Kalifrournia. Your gas is made with Bob Boudreaux's butt paste and vegetable oil, imported from the heads of famous imports like Alexi G Nooseuhm.

 

[xfadmin]

Are they supposed to be tan? White?
I replaced my two pre-catalyst oxygen sensors on my sport beetle today. Bosch 13721 from Rock Auto. About $72 each. Torqued to 35 lb-ft. The new sensors came with anti-seize on the threads.

View attachment 155174 View attachment 155175 View attachment 155176 View attachment 155177

I did this at 60K miles / 26 years old to solve code P1115. Feels gratifying. Got to use my O2 sensor thread chaser tool, my el cheapo-crows-foot wrench to torque, and my fancy shmancy gearwrench 90T stubby 3/8" ratchet.

View attachment 155182 View attachment 155181 View attachment 155180 View attachment 155179 View attachment 155178

However, the two old O2 sensors had a coating of white on them, like so:

View attachment 155183 View attachment 155184

What does everyone else's old O2 sensors look like? I looked up "white 02 sensor" on Google and one possible culprit is silicone poisoning if a silicone adhesive was used somewhere in the engine. I've never used a silicone based adhesive, although I have no idea what a prior owner used. I wonder if the issue is a too-lean-mixture?

9 months ago I had to replace my MAF because some CEL code popped up that said my MAF was faulty and making the mixture too lean. I cannot remember what the code was exactly, but I remember reading about it and the Motronic adaptation was too far out and couldn't adapt for the excessive leanness .... so I replaced the MAF. After replacing the MAF 9 months ago, the “too lean” CEL code never came back. So ... I wonder if these old O2 sensors indicate the mixture was indeed too lean .... or if they look normal? Thanks.

HOW-TO: Replacing M117 oxygen sensor | "HOW-TO" Tutorial Articles

Tonight I decided to replace the O2 sensor on my 560SEC. These are supposed to be replaced every 60K miles (although other models have varying replacement cycles). The US-spec 560SEC M117 uses a Bosch 3-wire O2 sensor. These are easily available through MB dealers or via parts.com, but are...

126board.com

 

[maw1124]

I always thought black O2 sensors meant rich mixture and white meant lean, but I can't remember where I got that from. Is that what we're concluding?

maw

EDIT… now I recall, that was for spark plugs as a test for coil packs. I wonder if it goes for O2 sensors as well.

 

[sheward]

That does apply to spark plugs so I assume it may be applicable to O2 sensors as they are just downstream of combustion.

 

[JC220]

Pull a spark plug too and see if the same white deposits exist.

May indicate lean running or fuel additives as Gixer said.

 

[Jlaa]

Hallelujah! Car runs awesome now. Except for the one cushion clamp that holds an O2 sensor wire to the body --- the inner plastic bushing disintegrated. Yes, just like fossilized 30 yo plastic Mercedes parts.

I got this to replace the cushion clamp:

https://www.amazon.com/gp/product/B096ZFYWZM

Anyways the car runs awesome now. Feels like I gained a boatload of part-throttle torque! For those that don't know, this particular model sport beetle (1996 USA spec) has a REALLY FINICKY OBDII system because it is the first year of the OBDII system. Meaning, the OBDII software is ..... um..... I bet there were too many P1s in Bugzilla before they shipped the product!!!

Anyways after resetting Check Engine lights, you have to do the following drive cycle, TWICE, with a COLD START, to get all the OBDII readiness monitors set (without which you will fail a smog test)

1) Start cold engine and idle for approximately 2 minutes, 10 seconds. This checks secondary air injection and evaporative leak detection systems.
2) Accelerate to 20-30 MPH and maintain steady speed for 3 minutes, 15 seconds. This establishes closed loop oxy-sensor operations, response times & switching times.
3) Accelerate to 40-60 MPH and maintain steady speed for 15-20 minutes. This evaluates catalytic converters while oxy-sensor response and switching times are checked.
4) De-accelerate and come to a stop. Idle in gear for 5-6 minutes. This checks evaporative leak detection system.

If any of the following events happened during the drive, then the drive is nullified and you have to start from a cold start again:

1) Engine speeds exceed 3000 RPM
2) Large fluctuations in throttle position
3) Road speeds exceed 60 MPH

Can you see how painful that is??!?!?! Drive for FIFTEEN minutes between 40-60mph without exceeding 3000 rpm. Do you have any idea how many road-ragers are on I-280, taking every chance to cut me off / flip me the bird / tailgate me mercilessly while I tool in the right lane at 55 mph??