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1983 380SL, ivory/dk brown, 46k miles, dual roller timing chain. 1986 560SL, red/white, 190K mile.
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7,068 Posts
Discussion Starter #481 (Edited)
Replaced the O2 Sensor with a Bosch 13925 equivalent to A0075425217 in my 1986 560SL.
When I purchased my 560SL back in 2013 the car had a spliced in O2 Sensor. In 2018 I purchased a Chinese made O2 Sensor off Ebay for $20. My 560SL has an slightly erratic idle - rpms up and down very slightly but enough to trigger my OCD. I suspected I should try a genuine probably made in Germany Bosch O2 Sensor AND ALSO I read some post where some mechanics were disconnecting the O2 Sensor to solve the erratic idle.

What I found is:
  • Sensor disconnected - idle acts the same
  • Bosch $71 sensor - idle acts the same, so I suspect that $20 O2 Sensor operates just find.
  • I just wasted about an hour of my time :)
In any case if you are wanting to replace your O2 Sensor, its not that big a deal to do it proper and not splice wires - so here are some pictures to show you how I did it.
BTW, these are pictures of how I did it the first time 2 years ago and I just did it this time exactly the same way.

Jack up right side of car:
Selection_988.png

The Connections are under the floor mats:
Selection_987.png

Behind this plastic cover:
Selection_986.png

Is this:
Selection_984.png

O2 Sensor wiring goes through a rubber grommet on the side of the Transmission Tunnel.
Push the grommet out and then push the wires so they fall out under the car.
I used these tools to remove the O2 Sensor - O2 Sensor removal socket, and hammer to strike the end of the ratchet:
Selection_980.png

Remove old O2 Sensor and screw in new O2 Sensor.
I used a little anti-seize on the threads of the new O2 Sensor.
Selection_981.png

As you are screwing in the new O2 Sensor, your wires dangling will twist too.
Its important that you tighten up the O2 Sensor so you don't get a big twist in the wiring.
Then feed the wires back through the hole in the transmission tunnel.
I found it easier dealing with the big rubber Grommet is to push it completely through the hole too, adjust the wire length so it doesn't dangle too much, then fix the big rubber Grommet in the hole while topside - much more room for your hands.

I also made sure the O2 Sensor had a good ground by running a separate wire from the Frame to the body of the O2 Sensor. I connected the wire onto the body with an ordinary Hose Clamp.

Clean your hands and go topside and make the connections like this:
Selection_984.png

Selection_985.png

Put the Plastic cover back on, Floor Carpets back and you are done:
Selection_987.png

Old Sensor versus New Sensor:
Selection_983.png
 

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'71 350SL, '76 450SLC (Euro both)
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273 Posts
Broke out the oxy-acetylene torch and silver soldered the top onto the expansion tank. Found a post on the "practical machinist" forum on how to do it. Practiced first on some cut up strips of brass. Got the right temp down and put it together. The real test comes when I start the car and put pressure on it.

p.s. never mind the spark plug wires. I just put them on and need the clips to sort them out.

2648647
 

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Premium Member
'72 350SL, '85 300D, '98 E320, '19 Subaru Outback (sold '14 GLK250)
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10,766 Posts
Broke out the oxy-acetylene torch and silver soldered the top onto the expansion tank.
When I learned to solder including silver soldering, we used blow torches! No oxyacetylene torch! Last time I did that, I was still in college.

15 years ago, the outer rims where the cap attaches had partly broken off on my brass tank. I could just get the cap to catch. I had a local rad shop do the repair. Not sure how they did it, but it came back painted and looking like new. They charged me for 0.7hrs labor. C$54. Still looks good!

Great that you are now getting to enjoy your car!
 

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1987 560 SL, 1990 300E 4Matic
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608 Posts
Broke out the oxy-acetylene torch and silver soldered the top onto the expansion tank. Found a post on the "practical machinist" forum on how to do it. Practiced first on some cut up strips of brass. Got the right temp down and put it together. The real test comes when I start the car and put pressure on it.

p.s. never mind the spark plug wires. I just put them on and need the clips to sort them out.

View attachment 2648647
Nice looking bead!
 

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1974 450SL, Dark_Blue/Parchment
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263 Posts
Ordered a front air damn from MAcarbon. It shipped last Thursday and should see it this Wednesday. This is a new one from Mercedes (560 type) and cheaper than I could find anywhere else. Been looking for a while and am looking forward to it transforming the front end of the Crazy B#tch!
 

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1987 300SL
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300 Posts
One good thing about this Covid iso, getting things done sooner than I expected
Just finished making some cribs, and partway through building a hardtop stand

2020-09-09 11.19.27-1.jpg
 

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1998 ML320, 1975 280C
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203 Posts
I sold my 107 Saturday.:):cry: Happy that it went to someone who really wanted a 450, and that I can now start looking for a GL350. Sad because I'll miss driving it, and tinkering with it trying to get everything back to a great running order.
The new owner should be signing up for here, as I gave him the info for the site.
 

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1987 560 SL, 1990 300E 4Matic
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608 Posts
Thanks to Martin(from Germany) posting a pic of his Kienzle head unit (which I had never heard of), I pulled the old p/o installed Alpine head unit and installed a new Kienzle CR1225 DAB+ head unit that I ordered from Germany via eBay. I kept the Rockford Fosgate amp, and Infinity speakers so it was plug, and play using the RCA jacks. I found out that the amp has separate gain controls for the front, and rear speakers so I was able to bring the gain up on the front speakers. The p/o had them adjusted down to almost zero.
Wiring was no problem either. I found that the MB connectors were long gone when I pulled the Alpine so I had to cut, and splice the new connector pig tails into the car side.

I like the Kienzle so far. It looks cleaner than the Alpine, and sounds better to me too.
Nate, it reminds me a lot of your head unit in your pic above.


2650177
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2650201
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'71 350SL, '76 450SLC (Euro both)
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273 Posts
I like that radio unit. I'm in the market for an update. Thanks for posting the info!
 

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1987 560 SL, 1990 300E 4Matic
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608 Posts
The display panel is actually dark in color when it's off as well as on. It appears light due to the camera flash.
 

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Registered
1983 380SL, ivory/dk brown, 46k miles, dual roller timing chain. 1986 560SL, red/white, 190K mile.
Joined
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7,068 Posts
Discussion Starter #498
@Nate Y , a suggestion ... Start a new Thread titled "Post a photo of your Aftermarket Radio". I think it would be
interesting seeing what other folks use. Might be a lot of cool radios out there like yours we are not aware of.
 

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1987 560 SL, 1990 300E 4Matic
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608 Posts
Carl, I think you meant your post for me. Good idea! It should be an interesting thread. I'll start one now.
 

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Registered
1983 380SL, ivory/dk brown, 46k miles, dual roller timing chain. 1986 560SL, red/white, 190K mile.
Joined
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7,068 Posts
Discussion Starter #500
Carl, I think you meant your post for me. Good idea! It should be an interesting thread. I'll start one now.
Yes indeed. I'm 72 and sometimes I get confused.
Looking for the new thead.
 
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