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Old 02-07-2005, 02:31 AM
86560SEL's Avatar
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Timing chain replacement on the turbo diesels?

Did a search and really did not find anything. I am wondering if the timing chain also has to be replaced on the turbo diesels as often as the gasoline engines? Also- are they interference engines? Meaning if the chain slips or breaks, will it destroy the engine? Thanks!

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Old 02-07-2005, 08:49 AM
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The OM616 and 617s are definitely interference engines. Loose the chain and you loose the cam, a few valves and a piston at the very least.

How frequently the chain should be replaced is a matter for debate. My 300D had about 270,000 on it when I replaced the chain (it had approximately 7 of elongation), the 300TD has appoximately 265,000 and only shows 4-5 of elongation. I haven't checked the elongation on my 240D (268, 000 miles) or my 300SDL (who knows how many miles!!!).
Never a dull moment at Berry Hill Farm.
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Old 02-07-2005, 09:00 AM
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I don't think they can "slip" but apparently they can break. Looking at them, it's almost hard to imagine them breaking - that's one tough chain!
'82 300SD - 361K mi - "Blue"

"Good judgement comes from experience. Experience comes from bad judgement."

listen, look, .........and duck.
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Old 02-07-2005, 09:42 AM
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Most of the breaks I have read of were at the master link, or where a crimped link was not crimped properly.
I had an acquaintance who bought one 300D I had considered buying, They were more decisive than I. Some time later their mechanic convinced them that their T/Chain needed replacing. They allowed him to replace it and 2 weeks later the new chain separated at the poorly crimped master link.
Just about broke their hearts. It was a peach of a 300D - IMMACUMATE.
Tony from West Oz.
Fatmobile 3 84 300D 295kkm Silver grey/Blue int. 2 tank WVO - Recipient of TurboDesel engine.
Josephine '82 300D 390kkm White/Palamino int.
Elizabeth '81 280E, sporting a '79 300D engine.
Lucille '87 W124 300D non-turbo 6 cylinder OM603, Pearl Grey with light grey interior

Various parts cars including 280E, 230C & 300D in various states of disassembly.
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Old 02-07-2005, 10:13 AM
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Let me preface this with a disclaimer. I don't have firsthand experience with any of this. This is all information I have read from various threads, shopmanual pages and websites while gathering information about changing the timing chain on my wifes 300D.

I don't think you'll find a single incident of a 616/617 timing chain actually breaking on its own.

Usuasually one of a couple of things happens
a) master link fails on a replacement chain.. either poorly crimped chain or misused clip link. (FYI the shop manual recommends using an unbroken chain on a rebuilt engine.)
b) chain rail breaks and gets jammed up in the chain and causes it to jump.
c) tensioner fails and lets the chain slack and jump. (older tensioner allows chain to jump?)
d) oilpump/vacuum pump fails and spews parts that jam the chain and cause it to jump. (older tensioner allows chain to jump?)

The 616 and 617 have a oil pressure controlled tensioner. Ont he 616 and early 617's if you lost oil pressure the tensioner could back off allowing the chain to slacken, increasing the risk of it jumping. Aparently MB decided rightfully so that this was a poor design. The newer 617's have the same tensioner, except it was redesigned to stop it from releasing tension with oil pressure loss.

It would seem to me that the tensioner backing off might allow the chain to jump if a rail came loose. The rails are plastic. Why wouldn't they just get chewed into little pieces by the chain and sproket. I wonder how many chains have jumped due to rails coming loose or other jam situations on engines with the redesigned tensioners compared to the old one?

I would think that the chain would be strong enough to just stop the engine if it jammed as opposed to jumping.

'84 300CD Turbo 132k (Anthracite Grey) - WVO - My daily driver - Recently named coo-coo-coupe by my daughter.
'84 300D Turbo 240k (Anthracite Grey) - Garage Queen
'83 300D Turbo 220k (Orient Red) - WVO - Wifes daily driver

I'm not a certified mechanic, but I did stay at a HolidayInn Express last night.
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