Remove/install piston rings

AR03.10-G-7311DD

Remove/install piston rings

15.08.2019

Engine

900.91/92 in model 000.001

Engine

902.91/93 in model 000.001

Engine

904.94/95/96/97 in model 000.001

Engine

906.90/93/94/95/96/98/99 in model 000.001

Engine

924.91/93/94 in model 000.001

Engine

925.9 in model 000.001

Engine

926.91/92/93/95/97/98 in model 000.001

1

Piston ring (keystone ring)

2

Piston ring (taper-faced ring with inside angle)

3

Piston ring (bevel-edged ring with garter spring)

3.1

Garter spring

4

Piston

5

Pliers

5.1

Screw

A

Spread value

 Caution

Risk of injury to skin and eyes due to handling of engine oil. Risk of poisoning caused by swallowing engine oil

Wear protective gloves, protective clothing and safety glasses.
Do not fill engine oil into beverage containers.

AS18.00-Z-0001-01A

Topical note

Notes on avoiding damage through contamination and foreign objects

AH00.00-N-5000-01H

Notes on work safety regulations for vehicles with natural gas-powered engines

AH00.10-N-1000-04A



Remove

1

Remove piston (4).

AR03.10-G-7021DD

2

Remove combustion residues on piston rings (1, 2, 3).

3

Clamp the connecting rod with piston (4) into the vise.


Use protective jaws for clamping.
The connecting rod can get damaged otherwise.

 Clamp in on the connecting rod.

4

Adjust pliers (5) using the screw (5.1).

  Adjust pliers (5) to max. spread (A).

Expanding value of piston ring

*BE03.10-N-1002-05J

 Pliers

*000589373700

5

Remove piston rings (1, 2, 3) with the aid of pliers (5) in sequence from top to bottom.

 Pliers

*000589373700



Check

6

Check piston rings (1, 2, 3) for chippings on coating.

If there is damage on one of the piston rings (1, 2, 3),



Replace all piston rings (1, 2, 3) of the respective piston (4).



Piston and piston rings changed
Engine 924.9 as of engine end number 810731, 926.9 as of engine end number 811140

BT03.10-W-0002-01A

7

Measure end gap of piston rings (1, 2, 3).

AR03.10-G-7311-02DD

Piston ring end gap

*BE03.10-N-1001-05J

If the wear limit is exceeded for one of the piston rings (1, 2, 3),



Replace all piston rings (1, 2, 3) of the respective piston (4).



Install

8

Adjust pliers (5) using the screw (5.1).

  Adjust pliers (5) to max. spread (A).

Expanding value of piston ring

*BE03.10-N-1002-05J

 Pliers

*000589373700

9

Insert garter spring (3.1) of piston ring (3) into the bottom groove of piston (4).



Pistons and piston rings changed

Engine 924.9 as of engine end number 810731, 926.9 as of engine end number 811140

BT03.10-W-0002-01A

10

Install piston ring (3) over the garter spring (3.1) using the pliers (5).

 Observe installation position, marking "TOP" must point toward piston crown. The garter spring offset from the garter spring end gap (arrow) must be offset relative to the piston ring end gap (3) by approx. 180°.

 Pliers

*000589373700

11

Install piston rings (2, 1) in the sequence from below to above using pliers (5).



Piston and piston rings changed

Engine 924.9 as of engine end number 810731, 926.9 as of engine end number 811140

BT03.10-W-0002-01A

 Observe installation position, marking "TOP" must point toward piston crown.

 Pliers

*000589373700

12

Install piston (4).

AR03.10-G-7021DD

Check values for piston rings

Number

Designation

Engine 900.9, 902.9, 904.9, 906.9 in model 000.001

Engine 924.9, 925.9, 926.9 in model 000.001

BE03.10-N-1001-05J

Piston ring end gap

Groove I Double-trapezoid ring

When new

mm

0,35...0,55

0,40...0,60

Wear limit

mm

1,0

1,0

Groove II Taper-faced ring with inner angle

When new

mm

0,40...0,60

0,40...0,60

Wear limit

mm

1,0

1,0

Groove III Bevel-edged ring with garter spring

When new

mm

0,25...0,50

0,25...0,50

Wear limit

mm

1,0

1,0

Check values for piston rings

Number

Designation

Engine 900.9, 902.9, 904.9, 906.9 in model 000.001

Engine 924.9, 925.9, 926.9 in model 000.001

BE03.10-N-1002-05J

Expanding value of piston ring

max.

mm

43

43