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Discussion Starter #1
Hey guys,

So, with this free time that we all have in our hands I decided to take a look under the car and do some preventive maintenance. I've known since I got this car a year ago that there's surface rust but upon inspecting the o2 sensor two things came to mind. First is, what are my chances of removing that o2 sensor? Feel like that thing might need to be torched. Second, upon looking at the picture I took up close I seem to have found a crack on the exhaust system which would force me to change the entire system. I'm going to get under it and use some soapy water to see if fumes are seeping out...

By the way, check engine has been on for a few weeks and I've noticed stronger fume smell lately.

Thanks!

-Eric
 

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1995 SL 500 2017 AMG GLC 43
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My O2 looked identical on my 95SL. Spray a good penetrating fluid over a few days and then get a good O2 removal tool with a long breaker bar. DO NOT think it will just unscrew easily. No matter what you think, it will eventually unscrew. It took me a long time with small turns and spray in between to get mine out. What a difference after the replacement. By the way, I really don't see a crack in your photo. I bought my O2 from Rock Auto. It was a Bosch replacement. Good luck.
 

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Hey Lee, big thanks for sharing your experience. Already ordered the Bosch replacement through Autohausaz. Guess all is left is some patience and perseverance. The exhaust seems to have a crack, if it's the case I'll use some exhaust repair paste instead of spending the big bucks and replacing the whole system.
 

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1991 300sl, 1993 Porsche 928 GTS, 1996 SL500, 1991 560sec, 1997 AMG C36
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Did our 96 SL500 couple years ago. I was concerned about the O2 tool splaying out and rounding the corners. Put the socket in place and put a worm gear clamp around the open end. If the sensor is toast, cut the cord and use a regular socket.
 

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2001 SL500
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You need to get your check engine light checked by someone with STAR .

Also I have the 6.5 inch door speaker you need.
 

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Discussion Starter #6
Thanks Phendriks, great idea using that worm gear clamp. I’ll work on it some time this week when parts arrive.

Tobi, I do have a O2 sensor code so at least I know I’m not shooting in the dark. As for the speaker, already got a pair. After a lot of asking and waiting I ended up moving forward with a pair of CDT from woofersetc with 2ohm impedance. Not sure how good the sound quality could have been with new OEM equipment but this was a huge improvement to what I was originally working with.
 

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1996 SL 500
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Hey guys,

So, with this free time that we all have in our hands I decided to take a look under the car and do some preventive maintenance. I've known since I got this car a year ago that there's surface rust but upon inspecting the o2 sensor two things came to mind. First is, what are my chances of removing that o2 sensor? Feel like that thing might need to be torched. Second, upon looking at the picture I took up close I seem to have found a crack on the exhaust system which would force me to change the entire system. I'm going to get under it and use some soapy water to see if fumes are seeping out...

By the way, check engine has been on for a few weeks and I've noticed stronger fume smell lately.

Thanks!

-Eric
The crack you see could be the shadow of the weld, i see some sulfate deposit, could be a crack
affecting the o2 sensor.
 

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Discussion Starter #8
Alright, so maybe suggestion is to fix the crack and see how it reacts. I'll update once done. Now, 93,xxx miles on the clock, should be due for an o2 swap.
 

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Discussion Starter #9
Hey guys. Had to tend to my business for a while and leave the car on the back burner. New o2 sensor in - car idles significantly better.

Exhaust leak? Nowhere to be found. Got fed up today and took it to a trusty benz shop and they couldn't find anything. Guys checked a second time with me when I got back to pick it up, nothing. I still feel it still has a strong exhaust/fuel smell that just wasn't there. Head mechanic would consider replacing injectors due to age... I'm thinking maybe I should do an emission inspection to see what comes up? Mechanic used a temp gun and pointed at both CATS, temp difference from one to another was small - his conclusion was that it's not the CATS. He also reset fuel parameters, car smelled the same when I parked it.

Mechanic shop is Karl's German Auto. Only works on MB or VW vans.

Thoughts?
 

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2001 SL500
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Hey guys. Had to tend to my business for a while and leave the car on the back burner. New o2 sensor in - car idles significantly better.

Exhaust leak? Nowhere to be found. Got fed up today and took it to a trusty benz shop and they couldn't find anything. Guys checked a second time with me when I got back to pick it up, nothing. I still feel it still has a strong exhaust/fuel smell that just wasn't there. Head mechanic would consider replacing injectors due to age... I'm thinking maybe I should do an emission inspection to see what comes up? Mechanic used a temp gun and pointed at both CATS, temp difference from one to another was small - his conclusion was that it's not the CATS. He also reset fuel parameters, car smelled the same when I parked it.

Mechanic shop is Karl's German Auto. Only works on MB or VW vans.

Thoughts?
Which o2 sensors did you replace
 

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1996 SL 500
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Hey guys. Had to tend to my business for a while and leave the car on the back burner. New o2 sensor in - car idles significantly better.

Exhaust leak? Nowhere to be found. Got fed up today and took it to a trusty benz shop and they couldn't find anything. Guys checked a second time with me when I got back to pick it up, nothing. I still feel it still has a strong exhaust/fuel smell that just wasn't there. Head mechanic would consider replacing injectors due to age... I'm thinking maybe I should do an emission inspection to see what comes up? Mechanic used a temp gun and pointed at both CATS, temp difference from one to another was small - his conclusion was that it's not the CATS. He also reset fuel parameters, car smelled the same when I parked it.

Mechanic shop is Karl's German Auto. Only works on MB or VW vans.

Thoughts?
You need to know, if it's exhaust or fuel smell, inside or outside.
Fuel smell could be EVAP system leak or fuel pump.
Seems MB German Karl should be your guy, use his nose.
 

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Discussion Starter #13
He did mention EVAP leak but you can't pick up any smell in the engine bay. It's definitely outside, the only way it gets inside is when you drive with windows/top down. Thanks for the input though.
 

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2001 SL500
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He did mention EVAP leak but you can't pick up any smell in the engine bay. It's definitely outside, the only way it gets inside is when you drive with windows/top down. Thanks for the input though.
Scan for an evap code. Last month I had P0442 for small evap leak. The most common cause is old gas cap. I replaced and code hast come back.

if you do the same (you should since the cap is old anyways) I recommend using the oe Blau cap like I did, as some members complained about the genuine cap getting stuck

 

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1996 SL 500
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You need to know, if it's exhaust or fuel smell, inside or outside.
Fuel smell could be EVAP system leak or fuel pump.
Seems MB German Karl should be your guy, use his nose.
OK if all checks out, one more not so obvious, the charcoal canister behind the left wheel liner.
 

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...By the way, check engine has been on for a few weeks and I've noticed stronger fume smell lately.
-Eric
Clarify exhaust smell from raw fuel (they are nothing alike).
My exeprience (different Make, 2001 car w/OBD2) CEL falsely attributed to a bad upstream sensor.
Reality: A leak in the fuel tank FILLER NECK that confused the computer to indicate bad O2.
 

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Discussion Starter #18
Had the chance to check out the charcoal canister. All lines look good in there, stuck my nose with the engine running and not a hint coming out of it. If anything it smelled a bit musty. Went over the engine bay once again ruled it out once again. I'm starting to think it'll be more fuel pump/tank related. You notice it by the rear wheels.

Maybe this offers a clue. When refueling with a low tank, as you remove the gas cap you hear pressure being released. Doesn't happen if you refuel with a half tank of gas.

Wheelr - fuel smell is predominant.
 

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Clarify exhaust smell from raw fuel (they are nothing alike).
My exeprience (different Make, 2001 car w/OBD2) CEL falsely attributed to a bad upstream sensor.
Reality: A leak in the fuel tank FILLER NECK that confused the computer to indicate bad O2.
How does a fuel tank leak ? Hole? Bad o ring?
 

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How does a fuel tank leak ? Hole? Bad o ring?
In my case (reminder, different make & model... and also 18yrs younger than my 30yo 300SL) was a deteriorated/bruised filler neck that led to tank.
Conjecture on what caused the bruising:
1 a lax clamp installation at the factory during the initial build that eventually "pinched" the neck
2 the neck shifted or realigned (a month before this leak developed, the car was at a repair shop, remaining on a lift in the AIR for about a week while parts came in).
Car was never hit and no rust.
 
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