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97 SL600 Pano, ex: 96 (late 95) SL320
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259 Posts
Discussion Starter #1
The internet is full of posts and instructions about repairing the throttle bodies on pre-facelift SL600s, but for the later version M120 I'm finding just about nothing. It's a totally different animal compared to the previous one and none of the videos etc I found helped at all.

I need to take mine apart to see if there's something obviously wrong inside, but I'm really struggling here. The reason I need to do this is that I think I finally found the reason to my long standing slightly uneven idle issue. Looking at the "smooth running" values in HHTWIN, one bank showed almost constant zeros as it should, and the other was fluctuating around 1-2 1/s^2. Swapping the throttle bodies moved the problem as well, so it seems pretty certain the issue is now isolated.

IMG_2160.jpeg

The first steps are easy. The cover on one side of the throttle body comes off easily, although somewhat annoyingly it's not bolted on but instead you need to bend some clips to take it apart. Next up, there's a big gear that just pops out. It takes a little courage but a bit of force does it. Then, to get to the electronics (and shaft seals, which are my suspect #1), you would need to get the butterly shaft out. The butterfly valve itself is held on with a couple of screws, no big deal. But then I ran into problems.

IMG_2174.jpeg IMG_2173.jpeg

The photos above show the ends of the shaft. One is the end where the springs are, and I would imagine that the shaft should slide out through that end. On the other end, however, the shaft ends in the metal bracket that holds the half gear. For the life of me I couldn't figure out how to get it off. I can't imagine anything besides excessive force would do it.

Any ideas?
 

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Registered
1994 SL500 1998 SL600
Joined
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151 Posts
The internet is full of posts and instructions about repairing the throttle bodies on pre-facelift SL600s, but for the later version M120 I'm finding just about nothing. It's a totally different animal compared to the previous one and none of the videos etc I found helped at all.

I need to take mine apart to see if there's something obviously wrong inside, but I'm really struggling here. The reason I need to do this is that I think I finally found the reason to my long standing slightly uneven idle issue. Looking at the "smooth running" values in HHTWIN, one bank showed almost constant zeros as it should, and the other was fluctuating around 1-2 1/s^2. Swapping the throttle bodies moved the problem as well, so it seems pretty certain the issue is now isolated.

View attachment 2613103

The first steps are easy. The cover on one side of the throttle body comes off easily, although somewhat annoyingly it's not bolted on but instead you need to bend some clips to take it apart. Next up, there's a big gear that just pops out. It takes a little courage but a bit of force does it. Then, to get to the electronics (and shaft seals, which are my suspect #1), you would need to get the butterly shaft out. The butterfly valve itself is held on with a couple of screws, no big deal. But then I ran into problems.

View attachment 2613104 View attachment 2613105

The photos above show the ends of the shaft. One is the end where the springs are, and I would imagine that the shaft should slide out through that end. On the other end, however, the shaft ends in the metal bracket that holds the half gear. For the life of me I couldn't figure out how to get it off. I can't imagine anything besides excessive force would do it.

Any ideas?
They look welded on both sides, I read on this forum that a company can rebuilt them but the easiest way would be getting a used S600 throttle body from Ebay like I did.
 

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Registered
97 SL600 Pano, ex: 96 (late 95) SL320
Joined
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259 Posts
Discussion Starter #3
Yeah, it certainly seems that way. I started looking for a new throttle body too.

I just didn't want to believe they went the "non-serviceable" route already back then. But already the fact that this newer version doesn't have screws holding the cover on kind of hinted that this might be the case...
 

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Registered
1994 SL500 1998 SL600
Joined
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151 Posts
Now I have no more throttle body error(s) but still a vacuum leak that I finally discovered after one month of searching! It is the lower portion of the three way check valve that goes from the crankcase to the brake booster. The problem is that I can't find the replacement part, not even from the dealer! I will end up adapting a check valve from the 500 and adding a T connection for the breather line.
 
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