My 92 400E(117.400k miles) has had some cold start issues lately and the exhaust started to smell like rotten eggs. so I figured the O2 sensor might be bad. I got he replacement part, but when I got under the car i found no room to get a wrench to the sensor. The thing is so jammed in between the two exhaust pipes leading to the catalyst, that there is almost no room to get to it. The CD manual doesn't tell me about any preceding work, but do I have to take off the catalyst to replace it, or use a special tool? Thanks in advance, F.J

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F.J.
81 300 SD grey/palomino 168K miles
84 190E 2.3 black/grey 64K miles (wrecked)
85 190E 2.3 maroon/palomino 92K miles
88 300E desert red/palomino 204k miles
(made to look like a '94-95)
92 400E desert taupe/creme beige 120K miles
(converted to 94-95 E420 looks)

F.J.

I just did this about 3 month ago on my 1992 400e.

You need an O2 sensor socket or 22mm open ended wrench. The sensor socket is the recommended way to go since you may strip the sensor if it is frozen in the threads with the wrench.

Believe it or not, there is a way to get the socket and ratchet in there. I lifted the DRIVER'S side and came in that way. I had better access coming in from this angle than when I tried with the pass. side lifted.

What I did was put the socket on the O2 sensor THEN I attached the ratchet to the socket. This way I had more room to move the ratchet around to get the best angle. Then I snapped on the ratchet to the socket.

It shouldn't be that hard. I think it took a total of 10 minutes for me to get the old one out and new one in.

Hope this helps.

Thank you very much for the reply, David.
What kind of socket do you mean when you refer to an O2 sensor socket?
Do I have to get it form the dealer or is it a regular tool?
Thanks again,
F.J.

__________________
F.J.
81 300 SD grey/palomino 168K miles
84 190E 2.3 black/grey 64K miles (wrecked)
85 190E 2.3 maroon/palomino 92K miles
88 300E desert red/palomino 204k miles
(made to look like a '94-95)
92 400E desert taupe/creme beige 120K miles
(converted to 94-95 E420 looks)

F.J.

The socket is available at most any auto parts store.

It is basically a regular socket with a cut-out for the sensors wires. Without the cut-out you would never be able to get the socket over the sensor since the wires would get in the way.

Hope this helps.

Thanks for the follow-up answer.
Damn, I have replaced quite a few oxygen sensors on mid '80s Mercedes 4's and 6's engine cars and never had to use such a tool. I have to admit I hadn't even heard of it. Ha,ha,ha! Ah well, you never stop learning. Such a tool makes a lot of sense in case of the 400E. No space in there.
Thank you very much again, your advice has been very educational and helpful. I'll let you know how things went.
Sincerely,
F.J.

__________________
F.J.
81 300 SD grey/palomino 168K miles
84 190E 2.3 black/grey 64K miles (wrecked)
85 190E 2.3 maroon/palomino 92K miles
88 300E desert red/palomino 204k miles
(made to look like a '94-95)
92 400E desert taupe/creme beige 120K miles
(converted to 94-95 E420 looks)

If your O2 sensor was bad, wouldn't your check engine light come on??

Also, isn't the rotten egg smell the result of a catalytic converter going bad?

(I may be wrong... but just trying to help...! )

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2006 E350 w/ 155k miles (Daily Driver)

Previous:
1993 300E 3.2L Sedan w/ close to about 300k miles
2003 E500 Brilliant Silver (Had 217k miles when totalled!)
1989 300E with 289,000 miles (had for <1 yr while in HI)
03 CLK 500 cabrio (Mom's)
2006 C230k (Dad's)
1999 S420 (Mom's/Dad's)
2000 C230k Sport sedans
2001 CLK320 Cabrio (Mom's)
1995 C280 My First Mercedes-Benz... (155k miles. EXCEPTIONAL AUTOMOBILE. Was Very hard to let go of!)

Good point, David.
I figured after almost 120k the Oxygen sensor was probably past due anyways and will try that before I go any further.
The "check engine"-light is , to my knowledge, exclusive to California cars. Mine is originally a N.J.-car and thus doesn't have it. Too bad, I got used to it, driving mostly California-version cars.
Thanks a lot for your thoughts.

F.J.

__________________
F.J.
81 300 SD grey/palomino 168K miles
84 190E 2.3 black/grey 64K miles (wrecked)
85 190E 2.3 maroon/palomino 92K miles
88 300E desert red/palomino 204k miles
(made to look like a '94-95)
92 400E desert taupe/creme beige 120K miles
(converted to 94-95 E420 looks)

Hi dsantos,
I got the tool today and it worked the way you described it. Really easy with that tool.
Damn, the sucker was tight, though.
The rotten egg smell is gone now and she even idles a bit smoother now.:p
Thanks a lot again.
F.J

__________________
F.J.
81 300 SD grey/palomino 168K miles
84 190E 2.3 black/grey 64K miles (wrecked)
85 190E 2.3 maroon/palomino 92K miles
88 300E desert red/palomino 204k miles
(made to look like a '94-95)
92 400E desert taupe/creme beige 120K miles
(converted to 94-95 E420 looks)

Glad to hear all is well now.