bearbrew

Soak everything down good with your choice of penetrating fluid and let it soak for at least a half hour. If you have the time let it soak longer or overnight if you can. Then take a pair of Vice Grips and remove what is remaining of the nuts. Sometimes you need to use a small sharp chisel and hammer and split the nut right next to the sensor. If I recall correctly these nuts have a larger diameter at the mating surface than the wrench flats and this is what is holding the sensor in place after most of the nut has rusted away. Clean the threads or use a thread chaser before you install the new sensor.

hypervish

The bolts on my sensor were rusted too and had completely disintegrated (you wouldn't even think that there was a bolt there before) , so i took a chisel and wedged it between the exhaust pipe and sensor as it was already kind of loose, and just lightly tapped it. Here's a few pictures:

Jerseyguy

I was out of town for several days and finally got back to this project today. I had sprayed the area with penetrating oil before I left, so it soaked for at least ten days.

It must've helped because I was able to get the sensor and the metal shield off the exhaust pipe with some gentle prying. That's when the fun started. The original gasket had rotted (and corroded) and only some of it came off. This left the surface uneven/lumpy. I assumed it should be relatively flat so the new gasket will make full contact with the pipe. I spent an absurd amount of time picking at, grinding and sanding it so that it's relatively flat and smooth.

Now to my current dilemma: the bolt threads are pretty cruddy and I don't have a thread chaser. I used various metal brushes and other amateurish methods to clean them up but nothing worked. I'm hesitant to try brute force with the new nuts because the dealer is a 25 minute drive away and wants $3.50 apiece.

I'm not familiar with thread chasers so I researched a little bit. Sears sells a 48 piece thread restoring kit for $69.99. This seems like overkill to fix just two bolts. There seems to be various other thread repair tools (files? hexagon die nuts?) but I don't know how well they'd work given the cramped area under there.

So, can anyone recommend an inexpensive solution or tool to clean up the threads? If a tool is absolutely required, I'd really appreciate a brand name/part number, a store, or even just a picture of what one looks like. I'm worried that I'll buy the wrong thing and damage the bolts beyond repair.

Also,does anyone know the size of the bolts? (10mm, 1.50 pitch?)

Thanks!

Hypervish - I think you meant the nuts (not the bolts) were rusted away. How did you get the new nuts onto the bolts? Were your threads clean enough to finish the job without a thread chaser?

hypervish

Yes, I meant the nuts were rusted away. I actually just used two random 12mm bolts lying around at my uncle's shop and slowly threaded them on, once i felt friction i just sprayed the stud with some WD-40 and then put some force on the nut with a wrench, and all was well.

tomf

Lexmex, Thanks for posting the pics. They provided needed information for me to change my sensor. Especially the pics for removing the seat and cutting the carpet. I ended up removing the seat and cutting the carpet. I figured no one will see the cut. Besides there was a cut already for some sort of vent.

The whole operation went smoothly. I did have a little trouble breaking the sensor free. I ended up using a 24 inch breaker bar.

I had error code P0136 on my ES300

RaphaelT

Thank you so much for the great pics and instructions, It only took about 4 mins to get seat out, and another 4 to get back in. It was also great to clean that area with a vac and clean the side of the console... Again many thanks... It took a total of about 30 mins for the job.

lserlohn

Thanks for all. It really helps me to save money in the future.

Naadrow

great write up

fanchius

How long will the oxygen sensor last in general? My RX300 2001 has 117,000 miles on. My mechanic shop changed timing belt set, water pump, and two drive belts, and cleaned throttle body at 114,000 miles, but the fuel efficiency dropped obviously by 7 %to 10% over the past five weeks. No leak was found. I guess the oxygen sensor (with a connector under the driver seat) was deteriorating, but no engine light is on for me to check the code at this point. Two air fuel oxygen sensors were replaced separately at 61,000 and 93,500 miles. Could any one advise me whether I need to wait till the engine light pops up, or replace the oxygen sensor now?

hypervish

Wait for the CEL. You don't need to waste the money. Plus, this oxygen sensor in particular won't improve mpg, it only provides feedback to the ECU about how much the exhaust is being "cleaned".

fanchius

Thanks hypervish, What could be the cause(s) for lower mpg?

tdandkd

I have the same problem as Jerseyguy. The nuts are completely rusted apart. I have sprayed everything down and will let it work for a few days. I'm hoping to gently pry the sensor off and anticipate having to pick pieces of the gasket off. the bolts look pretty corroded as well, so I was wondering if I should soak them again after I get the sensor out and then maybe even use something like they use in plumbing that fits over the bolts with a wire brush to try to clean them? If the new nuts don't go on, what is the next option?

ljwhitmire

Just have to give a heartfelt thanks to LexMex for this tutorial. I made it through the Air/Fuel sensors after several hours. I thought this part would be easy to change! I was about to pull by hair out
when I saw what needed to be done.

I'll knock it out this weekend thanks to the tutorial. Great Job!

boxbrownie

I was getting the dreaded code for a faulty sensor come on occasionally then it would disappear after a few days, this had been going on for months......so I bought a sensor for the time when it will need to be changed.
Arriving home on the drive one night I heard a faint "putting" from under the car, it was a slight exhaust leak.
Being a keen DIYer I took the car down to my local exhaust centre my mate Karl down there put it up on the ramps and found the sensor was blowing from the gasket seal, and no wonder the nuts had corroded away completelty and it was being held in place by crud! A few jiggles later and the sensor and shield came off leaving two very poorly looking studs on the exhaust boss, a few minutes with a thread runner and the remains of the nuts were cleaned from the threads. After refitting the sensor and some exhaust sealer as gasket all was well again.

Point is I never needed to use the new sensor, it turns out it was the very small air leak at the sensor mating face was upsetting the exhaust gas mixture and throwing up the code warning.

So if your lucky and getting this code take a squint underneath first and check if this is happening to you, if so its a quick and cheap fix, cost me the price of a couple of pints!

RoX300

LexMex, you rock.

Group, any suggestions on replacement bolts? I would prefer not to retool or rethread. Mine are close to unsalvageable.

Thanks,
RoX300