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1991 w126 420SEL, 1986 w126 Euro 560SEC (option 822), 2000 E55, 2003 E55, 2003 SL55
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512 Posts
Discussion Starter #1
I have been finishing many projects on the Euro and have done the second oil change since purchase. Decided to use synthetic and as the debate always goes I sprung a leak. I know! I Know! half the world is saying "I told you so" But to me to have a leak blocked with crust and sludge is not a correct way to seal it. Now to the question.
I have identified the source of the leak and it is the oil pressure sending unit on the passenger side of the block. From the looks this is a remove oil pan to get at. Looks easy enough but can someone confirm that it comes from the inside?

Thanks

Its been fun as I have gone through every seal on the trans when I did the transmission. One at a time as each one I replaced seemed to cause another:D, but when done you know they are good.
 

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1993 300TE, 1995 E320 Wagon
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I'm pretty sure your problem is a simple fix. I have the same issue, a slow drip from the sender plug. I'm going to try and attach the EPC page, but there are two seal rings that you need to get, numbers 77 and 74 in the pic, both part # 017 997 5748. The sender is held in to the side of the case by a lock clip, part # N91 20010 14001. I think you could probably do this without losing oil, as I think the level of the oil is about 6 inches below the hole. Hope this is the trick!
 

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Registered
1991 w126 420SEL, 1986 w126 Euro 560SEC (option 822), 2000 E55, 2003 E55, 2003 SL55
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512 Posts
Discussion Starter #3
So the seals are on the outside? It does not seem to make sense. One would think that the clip holds it in place but the seal would be between the unit (on inside of block) and the block. Then the clip would squish the seal between the block and unit. I would love to be wrong as it would then be a 10 minute job instead on a 2 hour job.

Thanks for the blow up.
 

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1993 300TE, 1995 E320 Wagon
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On second look, I checked out the manuals-- to remove the oil sender so you can put on the new seals, you do need to drop the oil pan, but just the lower one. Attached is the pdf with the visuals and instructions
 

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1991 w126 420SEL, 1986 w126 Euro 560SEC (option 822), 2000 E55, 2003 E55, 2003 SL55
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512 Posts
Discussion Starter #5
Makes sense. Thanks for the copy. Very helpful.
 

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Premium Member
2012 CL550 4MATIC Coupe
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9,992 Posts
Yeah, I just did mine. What Dave said. And BTW - That's the oil level sender, not the oil pressure. The oil pressure sender is on the side of the oil filter canister.
 

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1991 w126 420SEL, 1986 w126 Euro 560SEC (option 822), 2000 E55, 2003 E55, 2003 SL55
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512 Posts
Discussion Starter #7
Yeah, I just did mine. What Dave said. And BTW - That's the oil level sender, not the oil pressure. The oil pressure sender is on the side of the oil filter canister.
Thanks. I only looked at it an guessed what it was. Good to know. By the way I am excited for your project and have been following it. I know it is sometimes hard to see the long term when throwing cash at these cars it will be worth every penny I am sure. :bowdown:
I have become relentless in my pursuit of making this car everything it should be and it is driven by the motor. So impressive and if you think of the time this thing came out it makes it all the more impressive. When yours is done it will have the whole package. I hope to have the chance to meet up with much of the crew and share our rides someday in So Cal. I will be the first to toss my keys over for others to experience it. I am so obsessed I am looking for another SEC to drive "most of the time". While the SEL is great the SEC have that touch of performance in them with all of the class.
 

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W111 Coupe
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What oil grade have you been using? Clearances in these engines have been determined for grades available 25 years ago. Modern engines have much tighter clearances and use much thiner oils. Too thin oil in older engines in not that good. Make sure you have enough oil pressure at idle and that your timing chain is not rattling while starting your engine cold and warm, and at idle.
 

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CH4S Admin , Outstanding Contributor
1985 500SEC, 1991 190E 2.6.
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40,771 Posts
Elf Total fully synth 15/50.

Our engines see the most abrasive wear on start up, especially when cold.
You can get after market pre oilers. Not sure why manufacturers don't offer them.

For example, modern formula 1 engines are machined to extreme tolerances, and rev up to 19,000 rpm.
The blocks are warmed up, and the engines filled with operating temp oil and coolant, before they can safely be started.
 

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1991 w126 420SEL, 1986 w126 Euro 560SEC (option 822), 2000 E55, 2003 E55, 2003 SL55
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512 Posts
Discussion Starter #10
What oil grade have you been using? Clearances in these engines have been determined for grades available 25 years ago. Modern engines have much tighter clearances and use much thiner oils. Too thin oil in older engines in not that good. Make sure you have enough oil pressure at idle and that your timing chain is not rattling while starting your engine cold and warm, and at idle.
Royal Purple 20w 50.
 

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15w40, 20w50 or 15w50 must be fine, especially in AZ. I was under the impression that synthetic oils were thinner than that.
 

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1993 300TE, 1995 E320 Wagon
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Must be half a zillion threads on oil around here... I've been using whatever diesel oil is on sale at the local AutoZone or PepBoys for years (usually Mobil Delvac or Shell Rotella, this time round was Valvoline). I've read that the diesel oils still have the additives our gasser engines like. 3K miles on oil changes too, and Hengst filters... I compared Hengst vs. Mahle and found that Hengst has more folds in the paper element (equals more surface area).
 

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1991 w126 420SEL, 1986 w126 Euro 560SEC (option 822), 2000 E55, 2003 E55, 2003 SL55
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512 Posts
Discussion Starter #13
Must be half a zillion threads on oil around here... I've been using whatever diesel oil is on sale at the local AutoZone or PepBoys for years (usually Mobil Delvac or Shell Rotella, this time round was Valvoline). I've read that the diesel oils still have the additives our gasser engines like. 3K miles on oil changes too, and Hengst filters... I compared Hengst vs. Mahle and found that Hengst has more folds in the paper element (equals more surface area).
I agree. No more oil talk (right weight and ur good). That is why this thread was for info on the oil sending unit.
 
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