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Hello All,
I have a 1996 850 GLT wagon with a 5 speed manual transmission. The “Check Engine Light” came on. Went to my local mechanic and with a scanner he confirmed the front O2 sensor was dead. I asked him if it was necessary to replace the rear sensor too, and he replied “No”. Not that I want to spend money needlessly, but I recall reading or being told it was a wise practice that when one sensor failed, it was more prudent to replace both O2 sensors (front and rear) rather than the one that failed. Any comments/suggestions?
Secondly, my mechanic “cleared” the “Check Engine Light” but recommend replacing the front O2 sensor. I have an O2 sensor socket, and for the first time will try to replace an O2 sensor on my own. Assuming the “CEL” remains off, after I install the new O2 sensor, should I still disconnect the battery cable to keep the CEL off or just install the new O2 sensor?
Also, any suggestions/tips regarding the replacement of the front O2 sensor I would welcome with appreciation. Thank you to all who reply.
Hugh
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The front sensor went first on my car and would not budge after a long soak
with mystery oil and heating with MAPP gas. I gave up and took it to one of my
pro mechanic friends and he needed Oxy/Acetylene and heated it cherry red, and
with a big pipe wrench you should have heard the nasty noise of that O2 sensor
coming out so hard... like the screeching chalk on the blackboard. There was no way for me to get that critter out in the driveway. Have a plan B if you get stuck, a friendly mechanic or a muffler shop that will get it out for a fair price. It doesn't hurt to run a tap into the threads, I forget, maybe 8MM. I think its the same thd as the plugs. Use Never-Seez on assembly but don't get it on the sensor tip.
Good luck, Bill
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Bill,
Thank you. I have already told my private mechanic if I can’t get the sensor out, I will stop and bring it in for him to finish. I won’t “break anything”.
Although this is my first attempt, I’m hoping everything will go smoothly.
Hugh
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Hi Hugh,
So long as you have a Plan B available then "You're Jake"
You might want to put the MAPP gas on it, since heat goes a long way to
convince exhaust parts to loosen.
I'll be rubbing the beads to enhance your good luck.
Bill
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Bill,
Thank you for your advice and good wishes. Reluctantly, because of my false pride, I will reveal my ignorance and ask publicly: “What is MAPP gas?”
My game plan is to soak the O2 sensor with Power Blaster and let it sit for an hour before I try to unscrew it.
Hugh
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Hi Hugh,
No one knows everything, except maybe Known BS artists running for president.
MAPP gas can be used by Driveway wizards to heat stuff so it gets loose.
MAPP gas is hotter than propane
but not as hot as Oxy/Acetylene
You can get it at Home Depot, Lowe's etc. and maybe even Walmart, Its in a yellow
canister and it's more pricey too. Plumbers are using MAPP gas now since it heats up stuff faster. If you don't have a torch in your lool arsenal then
maybe now is the time to get one. I like the Benzomatic with the push-button starter which is fabulous as you don't need to mess around to get the torch lit.
When exhaust bolts and O2 sensors are welded stuck, heat is the savior.
Get the subject red hot before trying to bust it loose.
This is especially important with exhaust manifold and flange bolts that have a habit of snapping off instead of unscrewing....get em red, and try to bust em loose...not too hard , if they don't start, give em more heat, it takes time.
It's better than having to drill out some snapped off bolt.
Post back with your results with the O2 sensor. Perhaps it will just screw out
without any series of grunts and curses coming from under the car?
Bill
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Bill,
From your lips to God’s ears, I do not want to have to have this O2 sensor drilled out. My hope is the Power Blaster will loosen the threads and I will be able to back out the sensor. If I can’t get the sensor out, I will swallow my pride and have my local garage replace it. I just don’t want to make things worse or more expensive by my amateur efforts.
Hugh
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I don't think the sensor will snap off. It probably just needs lots of heat,
enough to turn it red. Exhaust bolts are a different story.
Don't fear, have at it.
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I bought a replacement O2 sensor from Amazon, the cheapest price around for OEM sensor. Part number: 9202719
Your mechanic is correct, the rear O2 sensor does not have to be replaced in tandom with the front. Just be prepared to replace it eventually.
Removal is easier with the NA engine. The plug for both sensors is on top of the tranny housing and is just visible from the engine bay. It helps to have long arms. The rear O2 sensor has a grey cover. The "top" of the plug is pryed upwards, you may have to use a small screwdriver to get it started. Once the top is up about 1/4 inch, the plug is easily pulled apart.
Follow the wire. The new OEM will have tape markings where the wires are attached to the body. I believe that at least one plastic zip tie is used, just cut it and remember to tie it up again when finishing.
Use liberal amounts of PB Blaster or some other penetrating oil on the O2 sensor and let it soak for at least 1 hour. Breaking it loose is the hardest part. Here is an FCP video that explains a lot, just scroll down the page until you see the video box:
https://www.fcpeuro.com/products/volvo-oxygen-sensor-front-850-c70-s70-v70-15097
The video is for a turbo, so you don't have to remove very much stuff. First get a flashlight and shine it down from the brake fluid reservior and get a visual of the sensor plugs.
I jacked my car up on the driver's side and slid headfirst under the car by the firewall. If you have a long breaker bar, hold the exhaust pipe with one hand and pull on the bar. Once you hear it pop loose, it should come out easily.
I just watched the video, he replaced both sensors. The front O2 sensor is not covered by the plate under the muffler.
--
My back feels better when I sit in a Volvo seat
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Klaus,
Thank you! After installing the new O2 Sensor, if the “Check Engine Light” remains off, is there any need to disconnect the battery cable?
Hugh
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There is no need to disconnect the battery before, during, or after. If the O2 sensor is working the light will stay off.
--
My back feels better when I sit in a Volvo seat
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Klaus,
Thank you for your advice about the FCP video. I looked at it last night. It seems the big challenge will be getting the plug out. I will use copious amounts of Power Blaster and let is soak for an hour as you suggested.
Also thank you advice about purchasing an OEM O2 sensor off Amazon.com. I never thought of that. I purchased one from FCP (Bosch) for nearly double the price listed on Amazon. Thanks to you, I know better. This knowledge will come in handy when the rear O2 sensor goes.
Hugh
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