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  #1  
Old 04-26-2007, 12:42 AM
250 Coupe's Avatar
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Location: Des Moines, WA
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M117 chain tensioner question

My 1976 450SEL with M117 diesels every now and then. At the next start, the timing chain rattles until oil pressure comes up.

I assume that the chain is slapping the tensioner back but wonder if the tensioner should resist being pushed back?

As I remember, the chain and guides were done within the last few years.

I'm trying to get rid of the dieseling but have not had much success yet.

CO at idle, .2
Timing at 0
Idle at 750 RPM
No vacuum leaks I can find
New plugs, old ones were clean, tan and only slightly worn.

Michael
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1971 250C 114.023 Sadly, it's been sold. I will miss it.
1976 450SEL 116.033 Maybe not so sadly, it's also gone. It was beginning fall apart more than I was willing to put it back together.
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  #2  
Old 04-26-2007, 01:00 AM
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is your chain good? you can change out the guides but if the chain is stretched you will still have a timing problem.
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  #3  
Old 04-26-2007, 04:21 AM
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Have you checked that the upper cam timing marks line up when at TDC?
Mine were way out due to the PO having the heads resurfaced at some point. I installed some offset keys to cure that problem. I actually chose offset keys to give me 1-2' more cam advance to make things more peppy.
Are you sure the rattle isn't lifter noise? I get that most times after the car has been sitting for more than a few hours. Disappears as soon as the oil gauge is pegged. I too have new guides, chain and a new tensioner.
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'85 500 SEL
'85 928S2
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'90 750i
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  #4  
Old 04-26-2007, 04:41 AM
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A thought towards your dieseling, you could have excessive carbon buildup in the combustion chamber.
There are cleaners available to try to remove it, thats applied through the air intake.
Then there is the old trick of dripping water down the intake to clear it out.
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'85 500 SEL
'85 928S2
'88 560 SEC
'90 750i
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  #5  
Old 04-26-2007, 08:15 AM
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Both my m117's rattled before the chain/guide/tensioner replacement- and the 560SL did for a bit afterwards also. I did have 10/40 oil and when I changed to 20/50 it stopped. That engine has about 260K on it I think.
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  #6  
Old 04-26-2007, 09:30 PM
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Quote:
Originally Posted by MTUpower View Post
Both my m117's rattled before the chain/guide/tensioner replacement- and the 560SL did for a bit afterwards also. I did have 10/40 oil and when I changed to 20/50 it stopped. That engine has about 260K on it I think.
I did just have the oil changed and it seems worse, maybe I should have asked for 20/50.

Michael
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1971 250C 114.023 Sadly, it's been sold. I will miss it.
1976 450SEL 116.033 Maybe not so sadly, it's also gone. It was beginning fall apart more than I was willing to put it back together.
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  #7  
Old 05-17-2007, 01:41 AM
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me too

Im doing this now checking marks ..I reused the valve cover gasket and it held but pretty hard ..I found a good source for 240d parts ..adjusting the valves made an instant differance I clearanced them (they were mostly too tight ..getting back to the timing chain do you recomend changing the tensioner and upper rub block as well>? also are there different qualitys of chain to buy? I can get one for 75 bucks and is money well spent cause my baby aint goin to the boneyard..sorry but you should park your car before the engine becomes a boat anchor by sounds of what I read..
thanks for simplifying the woodruff key for me I actually understand what you said better than technical jargon..
countryboys can survive 240D 4 speed 182.000 miles radio works blue vinyl mint silverbullet with one maroon hubcap that makes the chicks swivelneck!
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