Timing Chain Riveting & Press Tool Set – Mercedes M254 M256 – as W256589003900

This tool set is designed for cutting, pulling through, and riveting the timing chain on Mercedes M254 and M256 engines.

Due to the design and installation position of the timing chain, a dedicated special tool is required to safely perform the procedure.

Application Procedure

(Reference: Mercedes CLS C257 450 EQ Boost – M256.930)

Remove camshaft housing.
Set engine to top dead center and align camshafts to base position.
Loosen the last bolts only after camshafts are secured with locking tools.

Install the lever tool into the tensioning rail and mount it to the cylinder head.
Use the knurled nut to retract the tension rail.

Remove upper guide rail and timing chain idler gear.
Install chain holder and clamp the timing chain.

Remove rocker arm on cylinder 6.
Cover engine and openings.

Cut the timing chain using the installed riveting tool.
Connect old and new chain and pull through.
Rotate crankshaft using TDC tool while guiding chain.

Set engine to TDC.
Rivet the timing chain using the installed tool.

Torque Specifications

Camshaft housing: 1 Nm → 6 Nm → 6 Nm → +90°
Timing chain idler: 57 Nm
Upper guide rail pin: 20 Nm

Engine Compatibility

Suitable for Mercedes engines:

• M254
• M256

Tool Requirements

Additional timing tool set item.no. 121604 is required for proper operation.

Scope of Delivery

• 1 × Timing chain riveting and pressing tool set – as W256589003900
  • Includes: tension rail reset tool, chain holder, riveting tool with adapter and 3 inserts
• 1 × Adapter for chain cutting – as W254589003900

Reference and Notes

• Can be used as Mercedes tool as W256589003900
• Also referenced as W254589003900

OEM numbers are for reference purposes only. This product is not an original tool.

The design and installation position of the timing chain require the use of special tools (such as W256589003900 and W254589003900).

Please note that our timing tool set, Art. No. 121604, is additionally required.

Procedure – Timing Chain Replacement (cutting, feeding through, riveting)

(Reference: Mercedes-Benz CLS-Class (C257) 450 EQ Boost 4Matic with engine code M 256.930)

Preliminary Work

• Remove the camshaft housing
  • Set the engine to TDC and position the camshafts in their base position
  • Loosen the last 4 bolts (transmission side) only after the camshafts have been secured with a special tool
• Insert lever 1b into the timing chain tensioning rail and secure the holder to the cylinder head
• Use the knurled nut to push back the tensioning rail
• Remove the upper guide rail and the timing chain idler pulley
• Install chain holder 1c and clamp the timing chain
• Remove the rocker arm on cylinder 6
• Carefully cover the engine and all openings

Cutting the Timing Chain

• Use the timing chain riveting tool mounted on the cylinder head to cut the chain
• Ensure loose parts are controlled

Feeding Through the Timing Chain

• Connect the new chain to the old chain
• Release the chain holder
• Using the TDC positioning tool, rotate the crankshaft while a second technician guides the chain through
• Rotate the engine back to TDC

Riveting the Timing Chain

• Use the timing chain riveting tool mounted on the cylinder head to rivet the chain

Tightening Torques (if required)

• Camshaft housing: 1 Nm → 6 Nm → 6 Nm → +90°
• Timing chain idler pulley: 57 Nm
• Upper guide rail bearing bolt: 20 Nm