CHAINMB103 — MERCEDES-BENZ
CHAINMB103 on Mercedes-Benz: 31 steps, engines 103.940, 103.941, 103.942, 103.943. What to remove, in what order, and what to check after.
The M103 straight-six (103.940 to 103.985) found in the 190E 2.6, 260 E, 300 E and TE (including 4MATIC), 300 CE cabriolet, 260 SE, 300 SE/SEL and 300 SL uses a single-row chain that is normally renewed in place. The engine front cover comes off, the tensioner access plug is removed and the tensioner piston taken out so the chain goes slack. The old chain is split, the new one is connected to it and the engine is turned until the connecting link appears, then the ends are joined with the special tools. Two things decide the outcome: marking the running direction if the old chain is going back in, and checking the timing before the front cover is refitted.
🧭 Before you start
Remove the engine front cover and the tensioner access plug, then take out the tensioner piston. Split the chain, connect the new chain to the old one and turn the engine until the connecting link shows, then join the ends with the special tools. Check the timing, refit the tensioner and front cover with new gaskets.
Fits: platform codes 190E, 2.6, |, 260, E, 4MATIC, SE, 300, CE, CABRIO, -TE, -SEL, SL
Don't miss
- Mark the running direction of the chain if it is to be reused.
- Join the new chain ends with the proper assembly tools and inspect the link afterwards.
- Check the timing before refitting the engine front cover.
- Always use new gaskets on the front cover and access plug.
- Turn the engine by hand while drawing the new chain through; never force it with the starter, which is general workshop practice.
Written for this job from the workshop steps below · TorqFix editorial.
📐 18 workshop diagrams for 103.940
Real factory drawings for this job — timing marks, bolt locations and routing. Locked in the free view.
📋 Procedure
- Remove the special tools
- Remove the engine front cover
- If the timing chain is to be re-used, mark the running direction before removal
- Chain tensioner:
- Remove the access plug
- Always use new gaskets
- Remove the chain tensioner piston
- Check the timing
- Refit the engine front cover
- Disconnect the chain
- Connect the old chain to the new one
- Turn the engine until the chain connecting link shows
- Connect the ends of the new chain
- Use the special tools
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Ask about your Mercedes-Benz 103.940 — free → or sign up free to see the drawingsOther MERCEDES-BENZ procedures
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Who makes these pages, and how
TorqFix was built by a mechanic — after a 2,700 km drive with five roadside repairs that no diagnostic tool could explain.
The figures on this page come from manufacturer workshop documentation and are shown as they are. The page is assembled automatically from that data — it is not written by an AI. The AI works in the chat, where it answers for your specific car. It writes nothing here.
Variants of the same model differ. Cross-check torque against the factory manual for your engine before final tightening.
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The story behind TorqFix →Workshop data on this page last updated 20 Sep 2026.