Removing and installing pistons - RA03001193160X(03-3160)

Preceding work:

Removing engine (01-0300) .

Removing cylinder head (01-4150) .

Removing oil sump (01-3100) .

Operation no. of operation texts and work units or standard texts and flat rates

03-7021

Cylinder identification and piston identifications must agree (see arrows).

The pistons with numerals may be installed in a crankcase with a letter grouping, but not vice versa (see Pistons, matching and dimensions 03-3165).

When performing repairs, all the cylinder bores should be honed to the dimensions of the existing pistons plus piston play, see "Measuring, P03-2024-13 honing and silicone-lapping cylinder bores" (01-1120) .

The piston pins are matched to the pistons and must not be mixed up.

Fig 1: Identifying Piston And Cylinder Head Surface With Numerals

Courtesy of MERCEDES-BENZ OF NORTH AMERICA.

Fig 2: Identifying Piston And Cylinder Head Surface With Letters

Courtesy of MERCEDES-BENZ OF NORTH AMERICA.

This ensures that the specified piston play is maintained.

When performing repairs, all the cylinder bores should be honed to the dimensions of the existing pistons plus piston play (see table).

The piston pins are matched to the pistons and must not be mixed up.

Removing 

1. Unbolt conrod bearing caps and lift out conrod together with pistons.
   NOTE: Conrod and conrod bearing caps are marked together.

   

   Do not damage cylinder contact surfaces with conrod.

2. Inspect conrod bolts (03-3100) .
3. Use screwdriver to remove piston pin retainer and press out piston pin.
4. Service conrod and align, if necessary (03-3130) .
   Fig 3: Removing Piston Pin Retainer

   Courtesy of MERCEDES-BENZ OF NORTH AMERICA.

   Installing 

5. If pistons are worn, inspect gap and axial clearance of piston rings (03-3170) . Check that piston rings move freely. Pay attention to installation pos.: "Top" faces up.

   Distribute ring gaps evenly around circumference.

6. Oil piston pin and conrod bushes.
7. Install piston so that the arrow faces in direction of travel and the locking slots in the conrod (arrows) as well as the drawing of the conrod are facing to the outside of the engine.
   NOTE: The conrods are asymmetrical, the wide thrust collars point toward the crankshaft webs.
   Fig 4: Locating Locking Slots In Conrod

   Courtesy of MERCEDES-BENZ OF NORTH AMERICA.
8. Press in piston pin by hand.
   Fig 5: Pressing Piston Pin

   Courtesy of MERCEDES-BENZ OF NORTH AMERICA.
9. Insert piston pin retainer into the groove.
10. Oil cleaned cylinder bores, conrod bearing journals, conrod bearing shells and pistons.
    Fig 6: Locating Piston Pin Retainer & Groove

    Courtesy of MERCEDES-BENZ OF NORTH AMERICA.
11. Fit on tensioning strap for piston rings and insert piston into the cylinder bore with arrow facing direction of travel.

    

    Do not damage cylinder contact surface with conrod.

    Fig 7: Inserting Piston Into The Cylinder Bore

    Courtesy of MERCEDES-BENZ OF NORTH AMERICA.
12. Fit conrod bearing cap onto the conrod with the identification (arrow) facing each other. Moisten conrod nuts and thread and contact surface of conrod bolts with engine oil and tighten.

    Tightening torque (see 03-3100).

    

    Pay attention to installation position of conrod bearings. Install conrod bearing shell with oil drilling in the conrod otherwise lubrication of the piston pin is not assured.

    Pay attention to tightening torques of the conrod bearings (see Inspecting, replacing and tightening conrod bolts 03-3100).

13. Rotate crankshaft and check whether it rotates freely.
    Fig 8: Identifying Conrod Bearing Cap On The Conrod With The Identification Facing Each Other

    Courtesy of MERCEDES-BENZ OF NORTH AMERICA.

    Special tool 

    Fig 9: Identifying Special Tool (000 589 04 14 00)

    Courtesy of MERCEDES-BENZ OF NORTH AMERICA.