Rear Oxygen Sensor

[Poobah]

I am having my rear oxygen sensor replaced. As anyone who is familiar with the Northstar engine room knows, there is NO room to work between the back of the engine and the firewall. The old sensor isn't coming out. My mechanic has soaked it in WD40 (or something like it) and he has been able to turn it about 1/4 turn but no more. He thinks it is cross threaded in the manifold.

At this point, our only option seems to be to power it out with a breaker bar or gun. Of course, there is a real danger of destroying the threads in the manifold if we do this. If that happens, he said there is about a 30% chance we can successfully re-tap the threads and save the manifold. If that doesn't work, we'll have to R&R the rear exhaust manifold. This is, of course a time consuming job because there is just no room to work back there.

Have any of you run into this kind of problem? If so, any experience or advice you can share would be greatly appreciated.

Thanks in advance,

[johnnydone]

is there any way to apply heat to the manifold surrounding the sensor

[awise]

Poobah,

I did my O2 sensors a couple of months ago on my 98 Eldo-ETC. I was able to remove the one near the firewall (called Bank-1) by using the special O2 socket (has slot for the wires) and a long 1/2" drive extension. Then using a 1/2" drive ratchet I was able to get enough torque to break it loose and remove it. I know it should go without saying, but don't forget to disconnect the wire harness from the sensor prior to trying this. I know it sounds stupid to say it, but I had to any how.

Good luck!

Alan Wise

[Monaco500]

Hello Alan,

Perhaps there is more room between the back of the engine and the top of the O2 sensor on the '98; I got one of the slotted sockets (three different types, infact), but there isn't enough room between the top of the sensor and the back of the engine to slide the socket on. Did you use a special Cadillac O2 tool?

Thanks!

Eric

quote name='awise' date='Aug 10 2005, 01:37 PM' post='57586']

Poobah,

I did my O2 sensors a couple of months ago on my 98 Eldo-ETC. I was able to remove the one near the firewall (called Bank-1) by using the special O2 socket (has slot for the wires) and a long 1/2" drive extension. Then using a 1/2" drive ratchet I was able to get enough torque to break it loose and remove it. I know it should go without saying, but don't forget to disconnect the wire harness from the sensor prior to trying this. I know it sounds stupid to say it, but I had to any how.

Good luck!

Alan Wise

[Bruce Nunnally]

There was one on one of the cars that was located so that you had to lower the frame in order to have room to take out the o2 sensor (!)

Is the problem that the sensor is cross-threaded, or is the problem there is no room for it to come out?

Seems odd for it to get crossthreaded on the way out though.

[Poobah]

It's been over five months since my oxygen sensor adventure and some of the details have faded in my memory.

My mechanic, using the proper socket and a long extension bar, could only turn the sensor about a quarter turn before it bound up. He said he could work it back and forth a quarter turn but any more would require brute force. He thought the sensor had been cross-threaded when it was installed.

The extremely tight quarters around the rear manifold and the sensor hade it impossible to see what was going on or do any kind of work-around. He ended up taking the manifold off, which, if I remember correctly, required dropping the rear of the cradle. Once he had room to work on the sensor, he was able to get it out without ruining the manifold (a $450 +/- part).

This is one of those projects that looked like an easy fix in the begining but turned into a nightmare. Anyone who has worked on cars knows how this can happen. He managed to cut his hand quite badly on a heat shield or something in the process and had to take a day or two off.

This is an example of why I no longer do my own mechanical work. In the end, the Eldo runs fine, his hand and my bank account have healed, and, for a few days, I had the use of his exceptionally clean '89 Lincoln Continental coupe with 58K on the clock.

[growe3]

It is a tight fit, but I found that I could reach it from the top. I needed to unclip the wiring harness, and then I used 1/2" breaker bar with long extension, flex joint, and the special O2 socket.

The sensor binds to the manifold, and the best method is to use Penetrating Oil, WD40 is not going to do it. Allow the Penetrating Oil to soak over night.

You do not need to save the old wires from the SENSOR, after unplugging it, cut the wires off at the top of the 02 sensor. You can now use a regular, full sided, deep socket to remove the sensor.

When unscrewing the sensor, rock it back and forth until it unscrews without extra force. This will prevent the threads from being ripped out.

Be careful when starting the new sensor, it is very easy to cross-thread it. It is best to the re-tap the threads before putting in the new sensor.

Use patience, penetrating oil, patience, strength, patience, etc.

-George

[Monaco500]

Hey George,

Thanks for your help, but I have one question: The clearance between the back side of the engine and the top of the O2 sensor is so tight that even if I clipped the wires, I wouldn't have enough clearance to get a standard deep socket over the sensor. It looks like what is directly in my way is two steel (vacuum?) lines running along the back side of the engine. I would think that your car is similar (if not identical to mine - 93 and 94 STS). Did you have to remove anything to get clearance for a socket over the sensor?

Thanks!

Eric

It is a tight fit, but I found that I could reach it from the top. I needed to unclip the wiring harness, and then I used 1/2" breaker bar with long extension, flex joint, and the special O2 socket.

The sensor binds to the manifold, and the best method is to use Penetrating Oil, WD40 is not going to do it. Allow the Penetrating Oil to soak over night.

You do not need to save the old wires from the SENSOR, after unplugging it, cut the wires off at the top of the 02 sensor. You can now use a regular, full sided, deep socket to remove the sensor.

When unscrewing the sensor, rock it back and forth until it unscrews without extra force. This will prevent the threads from being ripped out.

Be careful when starting the new sensor, it is very easy to cross-thread it. It is best to the re-tap the threads before putting in the new sensor.

Use patience, penetrating oil, patience, strength, patience, etc.

-George

[BodybyFisher]

If you have the 2 dog bones holding your engine remove them, and get this tool and tilt your engine to gain some clearance. Any good tool shop will carry them, Mike

I especially love this statement at the ad:

Makes servicing spark plugs, hoses, oxygen sensor, and ignition components much easier. Holds the engine safely in place during service. Who da man....

PS, if you are handy, you can probably fabricate something in a pinch from all threads... to pull/tilt the engine

http://www.sjdiscounttools.com/lis48260.html

[Ranger]

Mike,

A hardware store turnbuckle will do the job. Thats what I used for my blower motor replacement.

[BodybyFisher]

Mike,

A hardware store turnbuckle will do the job. Thats what I used for my blower motor replacement.

Exactly Ranger! with the existing 4 bolts! I will keep that in mind... thx

[Bill K]

When I replaced the sensor on the Mtneer the manual said to run the engine and warm(expand) the manifold before removing as it made it easier.

[BodybyFisher]

When I replaced the sensor on the Mtneer the manual said to run the engine and warm(expand) the manifold before removing as it made it easier.

Good Bill, I had heard that also, makes sense also. Anyone know if anti-seize can be used without damaging the O2 sensor?

[growe3]

Hey George,

Thanks for your help, but I have one question: The clearance between the back side of the engine and the top of the O2 sensor is so tight that even if I clipped the wires, I wouldn't have enough clearance to get a standard deep socket over the sensor. It looks like what is directly in my way is two steel (vacuum?) lines running along the back side of the engine. I would think that your car is similar (if not identical to mine - 93 and 94 STS). Did you have to remove anything to get clearance for a socket over the sensor?

Thanks!

Eric

It is a tight fit, but I found that I could reach it from the top. I needed to unclip the wiring harness, and then I used 1/2" breaker bar with long extension, flex joint, and the special O2 socket.

The sensor binds to the manifold, and the best method is to use Penetrating Oil, WD40 is not going to do it. Allow the Penetrating Oil to soak over night.

You do not need to save the old wires from the SENSOR, after unplugging it, cut the wires off at the top of the 02 sensor. You can now use a regular, full sided, deep socket to remove the sensor.

When unscrewing the sensor, rock it back and forth until it unscrews without extra force. This will prevent the threads from being ripped out.

Be careful when starting the new sensor, it is very easy to cross-thread it. It is best to the re-tap the threads before putting in the new sensor.

Use patience, penetrating oil, patience, strength, patience, etc.

-George

The two lines are the metal coolant transfer lines. Some pressure can be made against them without damage to them.

I tried lowering the engine frame, to remove from the bottom, as described in the manual. This absolutely did not provide me any usable room to work. A big waste of time for me.

Removing a bolt from each torque arm (dog-bone) may be helpful. After removing the bolts, place a floor jack under the oil pan or the transmission oil pan (with a 2x6 board, or wider, to distribute the jacking pressure). Carefully jack the engine up, watching any "pinch points" Do not allow any items to press on to the heater barrier, it can crack easily.

Another item that was directly in my way was the rubber heater drain tube. It is placed directly above the sensor. With it pulled off you can see much better. It is troublesome to get the heater drain tube back on, but a little WD-40 on the top end helps it slip into place.

-George

When I replaced the sensor on the Mtneer the manual said to run the engine and warm(expand) the manifold before removing as it made it easier.

Good Bill, I had heard that also, makes sense also. Anyone know if anti-seize can be used without damaging the O2 sensor?

I'm not sure, but read the directions on any ant-sieze to be sure that it is 02 sensor safe. I just used a dab of moly engine assembly grease that I had handy, it provides good friction reduction when screwing the sensor back in.

-George

[Monaco500]

Thanks George,

I'm glad to hear that I can get enough clearance if I lift the engine from underneath. One question: Where can I get new bushings for the torque arms (dog bone)? Mine are cracked up pretty bad. I tried to describe them to the local auto parts store, but they didn't understand what I was talking about.

Thanks again for all of your help.

Eric

Hey George,

Thanks for your help, but I have one question: The clearance between the back side of the engine and the top of the O2 sensor is so tight that even if I clipped the wires, I wouldn't have enough clearance to get a standard deep socket over the sensor. It looks like what is directly in my way is two steel (vacuum?) lines running along the back side of the engine. I would think that your car is similar (if not identical to mine - 93 and 94 STS). Did you have to remove anything to get clearance for a socket over the sensor?

Thanks!

Eric

It is a tight fit, but I found that I could reach it from the top. I needed to unclip the wiring harness, and then I used 1/2" breaker bar with long extension, flex joint, and the special O2 socket.

The sensor binds to the manifold, and the best method is to use Penetrating Oil, WD40 is not going to do it. Allow the Penetrating Oil to soak over night.

You do not need to save the old wires from the SENSOR, after unplugging it, cut the wires off at the top of the 02 sensor. You can now use a regular, full sided, deep socket to remove the sensor.

When unscrewing the sensor, rock it back and forth until it unscrews without extra force. This will prevent the threads from being ripped out.

Be careful when starting the new sensor, it is very easy to cross-thread it. It is best to the re-tap the threads before putting in the new sensor.

Use patience, penetrating oil, patience, strength, patience, etc.

-George

The two lines are the metal coolant transfer lines. Some pressure can be made against them without damage to them.

I tried lowering the engine frame, to remove from the bottom, as described in the manual. This absolutely did not provide me any usable room to work. A big waste of time for me.

Removing a bolt from each torque arm (dog-bone) may be helpful. After removing the bolts, place a floor jack under the oil pan or the transmission oil pan (with a 2x6 board, or wider, to distribute the jacking pressure). Carefully jack the engine up, watching any "pinch points" Do not allow any items to press on to the heater barrier, it can crack easily.

Another item that was directly in my way was the rubber heater drain tube. It is placed directly above the sensor. With it pulled off you can see much better. It is troublesome to get the heater drain tube back on, but a little WD-40 on the top end helps it slip into place.

-George

When I replaced the sensor on the Mtneer the manual said to run the engine and warm(expand) the manifold before removing as it made it easier.

Good Bill, I had heard that also, makes sense also. Anyone know if anti-seize can be used without damaging the O2 sensor?

I'm not sure, but read the directions on any ant-sieze to be sure that it is 02 sensor safe. I just used a dab of moly engine assembly grease that I had handy, it provides good friction reduction when screwing the sensor back in.

-George

[BodybyFisher]

Try www.rockauto.com

[Ranger]

One question: Where can I get new bushings for the torque arms (dog bone)? Mine are cracked up pretty bad. I tried to describe them to the local auto parts store, but they didn't understand what I was talking about.

I don't think you can but the bushings seperately. I thought you had to buy the entire "dog bone". Ask for torque struts.

[BodybyFisher]

Sorry, they sell the entire dog bone, not the bushings, Larry is right. I didn't focus on your question, that you were referring to the bushings. You will be surprised how cheap the entire dog bones are..... I am going to replace mine also..