If the bolt in the (upper part of the) connecting rod is moving - first I say - good catch for someone who says this is the first time they've worked on an engine.

These bolts are not meant to turn - if they turn then they are likely to be slipping - if they slip the clearance won't be correct - if they slip now I wonder how long they'll stay put...

I think you are probably better off trying to buy new connecting rods with matching caps. But first you need to find a decent machine shop in your area that has done loads of Mercedes work for years and years... I know that that probably won't be easy... but if you can find someone - decent engine builder's advice is worth a lot. For example is the engine worth rebuilding?

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1992 W201 190E 1.8 171,000 km - Daily driver
1981 W123 300D ~ 100,000 miles / 160,000 km - project car stripped to the bone
1965 Land Rover Series 2a Station Wagon CIS recovery therapy!
1961 Volvo PV544 Bare metal rat rod-ish thing

I'm here to chat about cars and to help others - I'm not here "to always be right" like an internet warrior



Don't leave that there - I'll take it to bits!

Definitely a red flag and may require the offending rods to be changed out. The bolts can not have any play on them and the tight friction keeps them in place. If the bolt spins, it may mean the bolt bore had distorted to an oversized diameter.


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1983 123.133 California
- GreaseCar Veg System

my toque wrench was supper off and we ended up braking one of the connecting rod bolts. i'm about to remove some out off a old dead motor and i had a friends dad send me two new connecting rod bolts to replace the stretched ones

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84 300sd 2.47 dif 360k
26 mpg needs lots of love
given to me in pitty

89 civic hatchback auto 140k
33mpgs soon to be low to mid 40's
been in the family since mile 1

85 300d with unknown knock. driven over 30k with knock and still going. sold for $800