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Replacing o2 sensors?

Help, Advice and DIY Tutorials on Volvo's extremely popular car line -- Volvo's 1990s "bread and butter" cars -- powered by the ubiquitous and durable Volvo inline 5-cylinder engine.

1992 - 1997 850, 850 R, 850 T5-R, 850 T5, 850 GLT
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nadz
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Replacing o2 sensors?

Post by nadz » Sat Apr 09, 2011 11:50 pm

Hi,
Can anyone give me some detailed instructions on how to replace both o2 sensors? My car is a 1995 850 n/a. Pictures would be very helpful.
Thanks.



ratfink_v70_2000
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Re: Replacing o2 sensors?

Post by ratfink_v70_2000 » Sun Apr 10, 2011 3:52 am

All you need is an O2 socket. It has a cut out which allows it to slip over the wires then it's just a case of unscrewing like any other bolt/nut. At the other end is a plug and socket. Unplug old and plug in new.
Rich



VolvoTurbo850
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Re: Replacing o2 sensors?

Post by VolvoTurbo850 » Sun Apr 10, 2011 4:02 am

yes to that advice!

Keep in mind if yours is rusted on then it will be a real PITA to get it to budge. Also if the condition of the exhaust pipes are bad it could result in bending or splitting the pipe.

I often have my friendly neighbourhood exhaust guy do some of the work if it is not easy for me to do.



The Fleet

2001 V70 (NA) 2.5
1999 C70 Conv. Turbo 2.3 HPT
1998 S70 Turbo (T5) SE
1994 850 Turbo (T5)
1980 Corvette (Corvolvo)

Previous Possessions: (4) 240's, (1) 740, (9) 850's, (5) 70 Series
Projects on the go: NONE... Yet!

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Re: Replacing o2 sensors?

Post by vjaneczko » Sun Apr 10, 2011 8:34 am

Give them a squirt of PB Blaster the night before and then ten minutes before you tackle the job, it should go much easier. You might want to put a little anti-seize on them when you install them, too - you know, for next time :)


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thecheat
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Re: Replacing o2 sensors?

Post by thecheat » Sun Apr 10, 2011 8:37 am

First of all, get a torch and heat the bungs to cherry red, THEN use the o2 sensor socket. I broke a socket trying to remove my front one and was screwing around for over an hour with various tools before I dragged out the torch and had at it. Five minutes later it was backing out with a horrendous squealing noise!

I'm not sure if a plumber's torch will get it hot enough or not - supposedly there is a hotter gas than standard propane for the hand held torches.

You will need to make sure that there isn't oil in the wire strands of the old o2 sensor. If there is oil you have to get a harness from the dealer. What happens is that oil creeps into the strands and blocks airflow (the wires are channels for atmospheric air samples) and the sensor is ruined.



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Re: Replacing o2 sensors?

Post by db130 » Mon Apr 11, 2011 9:00 pm

i like to use a handheld mapp gas torch and the "crow's foot" type of o2 sensor tool. i've found that the slotted kind tends to flex more(i've cracked one in the past while trying to loosen a o2 sensor).


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nadz
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Re: Replacing o2 sensors?

Post by nadz » Mon Apr 11, 2011 10:40 pm

Thanks for the replies, but can someone explain this in a way for someone who knows nothing about cars, I don't even know where the o2 sensors are or how to access them.



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Re: Replacing o2 sensors?

Post by jblackburn » Mon Apr 11, 2011 10:47 pm

First, you'll need ramps to get the nose of the car up in the air. The two sensors are on located on top of the catalytic converter - one at the front, one at the back.

Try the easy method first - I was able to get mine loose with a shot of PB Blaster 10 minutes before I started and one good whack on the socket wrench. If you can't get anything to happen with brute force alone after a few minutes, then it might be time to resort to the torch. My car is a Southern one and hasn't seen much road salt in its life, so there's very little rust anywhere underneath.

The harness for the connectors was the tricky part for me (mine being a turbo with stuff in the way; yours should be slightly easier). It's wedged in the back of the engine behind the transmission. You will have to remove the bracket holding them in from below, and then jump up top and pull the pink/red part away from the black plug part with a screwdriver. Then the plug should simply slide out, but separating the two halves required quite a bit of force.

Are you sure your O2 sensor is bad? 95% of O2-sensor related codes are from vacuum leaks somewhere in the engine bay; if you've eliminated those and are still having problems. then go ahead with the replacement.


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nadz
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Re: Replacing o2 sensors?

Post by nadz » Wed Apr 20, 2011 8:55 pm

jblackburn wrote:First, you'll need ramps to get the nose of the car up in the air. The two sensors are on located on top of the catalytic converter - one at the front, one at the back.

Try the easy method first - I was able to get mine loose with a shot of PB Blaster 10 minutes before I started and one good whack on the socket wrench. If you can't get anything to happen with brute force alone after a few minutes, then it might be time to resort to the torch. My car is a Southern one and hasn't seen much road salt in its life, so there's very little rust anywhere underneath.

The harness for the connectors was the tricky part for me (mine being a turbo with stuff in the way; yours should be slightly easier). It's wedged in the back of the engine behind the transmission. You will have to remove the bracket holding them in from below, and then jump up top and pull the pink/red part away from the black plug part with a screwdriver. Then the plug should simply slide out, but separating the two halves required quite a bit of force.

Are you sure your O2 sensor is bad? 95% of O2-sensor related codes are from vacuum leaks somewhere in the engine bay; if you've eliminated those and are still having problems. then go ahead with the replacement.
Not sure if the o2 senor is bad, but I bought the sensors a while ago anyway. I still need to install them, but how would you check for vacuum leaks? I don't even know what to look for or where they are located.



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Re: Replacing o2 sensors?

Post by da7 » Wed Apr 20, 2011 10:20 pm

hi jblackburn: I'm interested to know the same, is there anywhere on the net that lists out all the vacuum hose connections that is prone to break or leak (pictures would be good) or do we just have to go crazy with the propane and spray it everywhere?



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