Piston: Service and Repair

11 25 530 Removing And Installing/Replacing All Pistons (M57T2)

Special tools required:







Necessary preliminary work:
- Remove engine.
- Remove cylinder head.
- Removing oil sump.
- Remove oil pump.







IMPORTANT: Re-install piston, connecting rod and bearing shells back in the same location and in the same installation position.
Connecting rods and bearing caps are designated with the same matching number: do not mix them.
Replace connecting rod bolts.







Unscrew connecting rod bearing cap.
Pull out connecting rod and piston to the cylinder head side.

IMPORTANT:
Position crankshaft vertically.
Proceed with care at the cylinder wall and oil spray nozzles Risk of damage.







Preliminary work:
Secure special tool 11 6 111 in vice.
Secure piston (1) with connecting rod to special tool 116 111.







WARNING: Safety goggles must be worn for the next operation.







WARNING: Safety goggles must be worn.

Lever out piston circlip with special tool 11 4 492 in direction of arrow.

IMPORTANT:
Piston and gudgeon pin are matched to each other.
They must not be mixed up.







Before installation, measure piston installation clearance. Measure piston diameter with micrometre at measuring point A from lower edge of piston and offset at 90°to the axis of the gudgeon pin.
Distance A,
Refer to Technical Data.







Adjust micrometre to cylinder bore of engine block. Set internal measuring device on micrometre to zero. Measure bottom,
centre and top of cylinder bore in direction of travel and direction of rotation.
Diameter of the cylinder bore,
Refer to Technical Data.
Piston installation clearance,
Refer to Technical Data.
Permitted total wear clearance,
Refer to Technical Data.







If necessary, replace connecting rods.
The BMW Parts Department only supplies connecting rods in complete sets.

NOTE: The gudgeon pin must be able to be pressed through the bush by hand with little force and must not display any significant play.







Replace connecting rod bearing shells.
Fit connecting rod to piston in such a way that both of the visible matching numbers on the arrow indicating direction of installation on the piston point to the right.







WARNING:
Safety goggles must be worn.
Insert piston circlip (2) into groove (1) of special tool 116 112.
Bring piston circlip into installation position.







WARNING: Safety goggles must be worn.

Guide lug and aperture on special tool 116 112 must point to piston crown; only then can special tool 11 6 113 be fitted correctly.

If special tools 11 6 112 and 11 6 113 are correctly positioned, the piston the circlip for gudgeon pin must be driven in with a plastic hammer in the direction of the arrow.

NOTE: See graphic.







Insert special tool 11 6 330 in connecting rod.
Lightly coat pistons and piston rings with oil.
Align contact points on piston rings (offset at approx. 120° but do not arrange over gudgeon pin boss).







Press together piston rings with special tool 11 8 140 .
Install piston so that arrow points to camshaft drive.

IMPORTANT: Risk of piston ring breakage.

Only press pistons in with finger force - do not knock in.







Attach crankshaft journal to connecting rod.
Remove special tool 11 6 330 .







Apply light coat of oil to connecting rod bearing shells.
Fit bearing caps so that matching numbers match up.

Installation note:
Use new connecting rod bolts.







Tighten down connecting rod bolts with special tool 00 9 120.

Installation note:
Tightening torque 11 24 1AZ.







The gasket thickness must be recalculated when repair work is carried out on the crankshaft drive or pistons.

Measuring the piston protrusion:
Fit dial gauge with measuring fixture special tool 00 2 530 on cleaned engine block sealing surface and set to zero under preload.







Position piston at TDC.
Clean piston at measuring points (1 and 2).
Fit dial gauge at measuring point (1) on piston and determine highest point by rotating crankshaft.
Measure and note down piston protrusion at measuring points (1 and 2) on all pistons.







The highest piston protrusion at the measuring points (1 and 2) of all the pistons determines the thickness of the cylinder head gasket.

Piston protrusion 0.92 ... 1.03 mm
- Install 2-hole cylinder head gasket.

Piston protrusion over 1.03 mm
- Install 3-hole cylinder head gasket.

Thickness of cylinder head gasket (1).







Assemble engine.
Check engine function and check for leak tightness.