BMW X5 Owners & Service Manuals

BMW X5: Piston With Rings And Pin

REMOVING AND INSTALLING/REPLACING ALL PISTONS (N52K)

Special tools required:

WARNING: Danger of injury!

Carry out work on piston pin circlip wearing protective goggles only.

IMPORTANT: If piston, connecting rod, big end bearing cap and connecting rod bearing shell are to be reused, they must be installed in the same position.

Individual replacement of a connecting rod is not permitted. Connecting rods are classified by weight categories and are only available as a set for all cylinders.

Connecting rod and big end bearing cap are marked with identical pairing letters and must not be mixed up.

Danger of engine damage!

Piston and piston pins are paired and must not be fitted individually.

Necessary preliminary tasks:

NOTE: Carefully remove heavy oil carbon residues from the cylinder wall (arrow).

IMPORTANT: Do not use any metal-cutting tools.

Piston With Rings And Pin
Fig. 122: Locating Cylinder Wall

IMPORTANT: Oil spray nozzle (2) must not be maladjusted or bent.

Risk of damage!

Do not release screw (1) of oil spray nozzle (2).

If necessary, readjust oil spray nozzle (2).

Piston With Rings And Pin
Fig. 123: Spray Nozzle And Screw

Release conrod bolts (1).

Tightening torque: 11 24 1AZ.

Installation:

Replace screws.

Remove conrod bearing cap (2) in direction of arrow.

IMPORTANT: Connecting rod and big end bearing cap (2) are marked with identical pairing letters and must not be mixed up.

Danger of engine damage!

Piston With Rings And Pin
Fig. 124: Removing Conrod Bearing Cap

Attach special tool 11 8 330 to connecting rod.

Press out connecting rod and piston with special tool 11 8 330 to cylinder head side.

NOTE: Special tool 11 8 330 simultaneously serves to prevent connecting rod and piston from falling down.

IMPORTANT: Do not touch the oil spray nozzle when removing the components.

Risk of damage!

Piston With Rings And Pin
Fig. 125: Special Tool (11 8 330)

Preliminary work:

Clamp special tool 11 4 491 in vice.

Secure piston (1) with connecting rod to special tool 11 4 491.

Piston With Rings And Pin
Fig. 126: Securing Piston With Connecting Rod To Special Tool (11 4 491)

WARNING: Danger of injury!

Carry out work on piston pin circlip wearing protective goggles only.

WARNING: Protective goggles must be worn.

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

Piston With Rings And Pin
Fig. 127: Removing Piston Pin Circlip With Special Tool (11 4 492)

If necessary, replace connecting rods.

IMPORTANT: Individual replacement of a connecting rod is not permitted. Connecting rods are classified by weight categories and are only available as a set for all cylinders.

Existing and new connecting rods must not be installed in mixed combinations.

Installation:

It must be possible for the piston pin to be pressed with minimal force by hand through the small end bushing.

There must be no noticeable play.

Piston With Rings And Pin
Fig. 128: Installing Piston Pin Into Small End Bushing

Measure piston installation clearance: Measure piston diameter with micrometer at measuring point "A" from lower edge of piston and offset by 90º to piston pin axis.

Piston diameter at measuring point "A".

Piston With Rings And Pin
Fig. 129: Measuring Piston Diameter

Adjust micrometer to cylinder bore of crankcase. Set internal caliper on micrometer to "zero". Measure bottom, center and top of cylinder bore in direction of travel and direction of engine rotation.

Diameter of cylinder bore.

Piston installation clearance.

Total permissible wear toleranc.

If necessary, replace piston.

Piston With Rings And Pin
Fig. 130: Measuring Diameter Of Cylinder Bore

WARNING: Protective goggles must be worn.

Insert piston pin circlip (2) into groove (1) of special tool 11 4 493.

Move piston pin circlip (2) into installation position.

Piston With Rings And Pin
Fig. 131: Piston Pin Circlip And Groove

WARNING: Protective goggles must be worn.

Guide lug and cutout on special tool 11 4 493 must point to piston crown. Only then can special tool 11 4 494 be correctly fitted.

When special tools 11 4 493 and 11 4 494 are correctly positioned, the piston pin circlip must be driven in with a plastic hammer in the direction of the arrow.

Piston With Rings And Pin
Fig. 132: Installing Piston Pin Circlip

NOTE: For vehicles with B30 engines.

Install all piston rings.

Install all connecting rod bearing shells.

Coat piston (2) and piston rings with oil.

Pre-install piston (2) in special tool 11 6 261.

Attach special tool 11 8 330 to connecting rod (1).

Installation:

Check protective lugs on special tool 11 8 330 for correct position and damage.

Piston With Rings And Pin
Fig. 133: Connecting Rod, Piston And Special Tools (11 8 330) And (11 6 261)

NOTE: For vehicles with B25 engines.

Install all piston rings.

Install all connecting rod bearing shells.

Coat piston (2) and piston rings with oil.

Pre-install piston (2) in special tool 11 6 241.

Attach special tool 11 8 330 to connecting rod (1).

Installation:

Check protective lugs on special tool 11 8 330 for correct position and damage.

Piston With Rings And Pin
Fig. 134: Connecting Rod, Piston And Special Tools (11 8 330) And (11 6 241)

Insert piston (1) with connecting rod in cylinder.

IMPORTANT: Do not touch the oil spray nozzle when installing the components.

Risk of damage! Danger of piston ring failure.

Press in piston (1) at marked points (see arrows) with finger pressure only, do not drive in.

Insert piston (1) so that arrow (2) on piston crown points to camshaft drive.

Press in piston (1) with special tools 11 6 261 / 11 6 241.

Piston With Rings And Pin
Fig. 135: Pressing Piston With Special Tools (11 6 261)

IMPORTANT: Connecting rod and big end bearing cap are marked with identical pairing letters (1) and must not be mixed up.

Mixing them up or incorrectly fitting the big end bearing cap on the connecting rod will result in engine damage.

Piston With Rings And Pin
Fig. 136: Connecting Rod Identical Pairing Letters

Apply a light coat of oil to connecting rod bearing journal. Join connecting rod and connecting rod bearing journal.

Detach special tool 11 8 330.

Piston With Rings And Pin
Fig. 137: Special Tool (11 8 330)

Fit conrod bearing caps (2) so that pairing letters match up.

Installation:

Replace screws.

Install new conrod bolts (1).

IMPORTANT: Jointing torque and angle of rotation must be observed without fail.

Risk of damage!

Tightening torque: 11 24 1AZ.

Piston With Rings And Pin
Fig. 138: Conrod Bolts And Connecting Rod Bearing Cap

If necessary, tighten connecting rod bolts to torsion angle with special tool 00 9 120.

Tightening torque: 11 24 1AZ.

Piston With Rings And Pin
Fig. 139: Special Tool (00 9 120)

Assemble engine.

REPLACING PISTON RINGS ON ALL PISTONS (N52K)

Necessary preliminary tasks:

Measuring axial clearance of piston rings in piston ring groove.

Technical Data.

NOTE: It is not possible to measure the axial clearance of the U-flex rings.

Piston With Rings And Pin
Fig. 140: Measuring Axial Clearance Of Piston Rings In Piston Ring Groove

Remove plain compression ring and stepped ring upwards with piston ring pliers.

The U-flex ring comprises two steel band rings and a support spring.

NOTE: The U-flex ring cannot be removed with piston ring pliers.

Put aside all piston rings in correct sequence and installation position.

It might not be possible to find the identification on used piston rings.

Installation:

New pistons may only be installed together with new piston rings.

Piston With Rings And Pin
Fig. 141: Removing Plain Compression Ring And Stepped Ring With Piston Ring Pliers

Determine end clearance with a feeler gauge.

Piston With Rings And Pin
Determine end clearance with a feeler gauge

NOTE: Schematic diagram of piston rings.

Installation:

Piston rings with "TOP" identification must point to piston crown.

  1. Plain compression ring
  2. Stepped ring "TOP"
  3. U-flex ring

Piston With Rings And Pin
Fig. 143: Piston Rings Installation Position

NOTE: The U-flex ring comprises two steel band rings (1) and a support spring (2).

Installation:

Insert support spring (2) into piston ring groove and then fit steel band rings (1) so that contact points are offset by approx. 120º.

Piston With Rings And Pin
Fig. 144: Support Spring And Steel Band Ring

The contact points (1) of the piston rings must be arranged offset by approx. 120º. However, the contact points (1) must not be arranged over the piston pin boss.

NOTE: Picture shows N52.

Piston With Rings And Pin
Fig. 145: Contact Points Of Piston Rings

Assemble engine.

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