02 Sensor - CLEAN or REPLACE??

So - what exactly is it that 'goes bad' on an O2 sensor?? Just looking at the price of a new one $65+ makes me think it might be worth it to pull the old one and give it a good bath or cleaning or something - but that assumes I know jack about the 02 sensor - which I don't...!


Anybody have any info on these?


Thanks.

I'm sure someone will tell you they cleaned theirs and it fixed everything from bad mileage to world hunger, but for the money I'd just change it. The semi-precious metals used in them to generate the signal (diferent depending on type) do have a lifespan and will wearout over time and use.
.02 blah, blah, blah......

--Shorty:conceited

okay - makes sense. I just thought there was an off-chance that it gets replaced, when most times it could just be cleaned out due to soot. I'm also in the middle of trying to change my coolant. NOT as much fun as I was hoping!!!

Maybe I should just drop it off at a lube joint and have THEM do it...! (what are the chances they'd do it properly, though??)

I bought mine off eBay. $35.00 for direct replacemet. If you do not mind re wiring the connectors, the generic are about $25.00

My 97 does run smoother after replacing the originals at 150K.

Good luck.

The sensing element of the HEGO is a "semi-exotic" ceramic, which is porous to allow the exhaust gas to be checked against a sample of atmospheric air. This ceramic is what gets plugged up (usually with carbon,) and it becomes not porous. I'd be almost willing to bet that the typical HEGO really can't be cleaned, unless all the carbon is on the surface.

That's part of why they've come up with "thin-film" HEGO sensors, since you don't have to depend on a porous ceramic capsule - and because they heat up faster than the typical HEGO (less material.)

But yeah, considering the money involved, I'd just replace the thing. It's easier...

Any silicon, just the tiniest bit, will destroy the O2 sensor. I don't know if there are other common chemicals that will hurt it, but they are a very sensitive instrument. So, I get the impression that taking it out and scrubbing it with soap and water, or spraying solvents into it or blowing high pressure air into will just hurt it far more than help it with soot removal. I dont' know for sure, thats just my guess, but I'd just replace the O2 sensor with new.

I have a few thoughts on this, and some of your comments have gotten me thinking so here goes:

I was just researching this and talking to a Bosch engineer last week. Here is what I know.
1) The silicates (silcone) in antifreeze are death for an O2 sensor.
2) Silicone caulk or silicone lubes like spary on silicone are death for an O2 sensor
3) Silicone antisieze is death to one.
4) Any soap with silicates in it (which is very common) is death to an O2 sensor. Many cleaners like Fantastic, 409, most alkaline cleaners-detergents, cloths washing soaps, many alkaline steam cleaner soaps, some car soaps, have sodium metasilcate, most antifrezeze formulas have sodium metasilicate, and they all will kill an O2 sensor.

Aparently the silicone, or silicates can react permanently with the O2 reactive sensor materials thus deactivating them permanently.

That said, a good solvent based solution like seafoam, B-12, etc., keroseen, maybe deisel fuel, used as soak cleaner followed by a 500 F oven bake to remove carbon might work if the problem is carbon fouling and silicone contamination.

Also, a non silicated solvent based cleaning solution used in an ultrasonic cleaner* might work great (*which we used for cleaning deisel fuel injectors that were previously going to be tossed as I recall, for the first time back in the 1970's ). I would still do the oven bake after cleaning with the ultrasonic cleaner. Might even do both steps twice just to get all the carbon out.

Of course, the question would be is it worth the time and trouble for one O2 sensor? But for these newer vehicles with 4, $100 sensors, it might be worth the trouble ($400).

Anyway, any nonsilicated, non silicone, pure solvent cleaner should be ok, including brake cleaner (the old chlorinated or the new non chlorinated ones.)

It also might be a good idea (cleaning) to improve the O2 sensor response time which degrades slowly with age! That would increase ones MPGs. Shame they are not easier to get to on our older jeeps. My sons ford 96 Taurus O2 sensor is a 5 minute job standing up.

Maybe some some younger, boared, bright young mind out there will read this thread, gather a few bad O2 sensors, clean them like I suggested above and them bench test them with a multimeter to make sure they are bad, then clean them as suggested above then use a propane bottle bench test set up with a multimeter and see if cleaning them brought them back to life?

And then of course tell the rest of us lazy know it alls how well (or not well) it worked. If that were to happen, that person should test the O2 sensors first on the bench to verify that they were dead, before they were cleaned!

Anyone out there dying to run a few cleaning tests?

One last thought, if you get silicone or antifreese on one of these, try triple washing it with DI water several times followed by several good solvent washes and you might still salvage the sensor. Once the sensor gets heated up (over 600 F, in fact I think it is more like 1000 F at the sensor tip where the internal HEGO heater is) the silcone reacts with the sensor elelments and then it is permanently shot, then no washing will fix it.

Ecomike said:

....I was just researching this and talking to a Bosch engineer last week. Here is what I know.
1) The silicates (silcone) in antifreeze are death for an O2 sensor.
2) Silicone caulk or silicone lubes like spary on silicone are death for an O2 sensor....

Click to expand...

Dexcool and many of these new "Extended Life" anti-freezes (OAT Technology) do NOT contain any silicates. The silicates are what deplete within 2 years requiring the replacement of the anti-freeze. They use other additives that promote and preserve the natural protective coat of corrosion that forms on the parts. Unfortunately, it looks like a lot of people are being snowed into thinking they are buying old fashioned "Green" (IAT Technology) anti-freeze that is recommended for their vehicle, but instead are getting a derivative of Dexcool dyed green.

G-05, (HOAT Technology) should NOT have any silicates either, but some of the manufacturers are adding a little silicates with the G-05 to provide some extra protection.

Many of the RTV Silicone Sealants say they are "Sensor Safe", I often wonder how they can be if they are silicone? Any insight on this?

BTW, I only use RTV that says its "Sensor Safe" anywhere on the engine, tiny bits can break off and migrate to other parts and find its way into the sensor.

If your XJ is latter model, and you don't have too many miles on the sensor (<30-50000), and depending on why it's not working, you may be able to clean it with a propane torch. Place the sensor in a vise (gingerly!!) and play a high flame over and all arround the tip--it will turn bright red. This will possibly burn off any contamination. Then connect a digital volt meter to the out put lead. Re-heat as above. You should see ~1 volt DC. When you remove the torch, the output should drop rapidly to zero volts. There are parameters regarding time required to rise to max output (~1 volt) and drop back to zero--they're in my notes someplace, or included in web articles regarding O2 sensor operation.

xjbubba said:

If your XJ is latter model, and you don't have too many miles on the sensor (<30-50000), and depending on why it's not working, you may be able to clean it with a propane torch. Place the sensor in a vise (gingerly!!) and play a high flame over and all arround the tip--it will turn bright red. This will possibly burn off any contamination. Then connect a digital volt meter to the out put lead. Re-heat as above. You should see ~1 volt DC. When you remove the torch, the output should drop rapidly to zero volts. There are parameters regarding time required to rise to max output (~1 volt) and drop back to zero--they're in my notes someplace, or included in web articles regarding O2 sensor operation.

Click to expand...

I agree with this.

A chlorinated solvent wash (perchlorethylene or trichlorethylene in the spray bottle), or a carburator cleaner (mostly MEK and Toluene) spray wash before and after the propane torch cleaning should help too. They are great at disolving tenacious carbon deposits.

I posted a good testing proceedure here just last week in two of the old O2 sensor threads in this forum, including differences between the Renix O2 sensors tests and the 1991 and newer O2 sensor tests. The pre 1991, Renix era, O2 sensor is a 5 volt system, whereas the newer ones use a 1 volt system. (5-90 clued me into this and I verified the testing procedure from a Bosch O2 sensor engineer).

The pre 91 sensor needs to be hooked up to the Renix ECU to get a 5 volt input signal. Then it oscilates between 1 to 4 volts as the O2 concentration rises and falls. It acts more like a variable resistor.

The 91 and newer O2 sensor produces its own 0-1 volt output signal.

I ran across a Preston Coolant engineer back in 1996 that said they had replaced the Silcates with Borates in their newer (at the time) extended life coolant. Don't know if they stayed with it or not. Their standard colant still had silicates at the time.

Don't know about the RTV safe silicone claim. You could always try wiping some on your O2 sensor to see if it kills it or not, LOL, and let us know what happened.:bawl:

Seriously, it may be safe after it has cured, but I do not know for sure. We do use silcone spark plug wires (cured) under the hood and they get pretty darn hot, so they are not giving off any O2 sensor toxic fumes. I sure would not try putting it on an O2 sensor wet, and then fire up the engine. I would expect sensor safe silicone RTF to still damage the porous ceramic in that case.