Remove/install piston rings

AR03.10-W-7311C

14.11.05

ENGINE 457.9 in MODELS 374, 375, 940, 942, 943, 944, 958

W03.10-1037-06

Illustrated on model 944

1 Piston ring (keystone ring)

2 Piston ring (taper-faced ring with inside angle)

3 Piston ring (bevel-edged ring with spring expander)

3.1 Coil spring

4 Pistons

5  Pliers

5.1  Knurled screw

A Spring expander offset

B Spread value

Arrow: Coil spring end gap

Modification notes

20.5.05

Measure piston ring end clearance - added.

Step 7

AR03.10-W-7311-02C

	Removing
1	Remove piston (4)		AR03.10-W-7021C
2	Remove combustion residues on piston rings (1, 2, 3)
3	Clamp connecting rod and piston (4) in a vise	 Use protective jaws for clamping.
4	Adjust pliers (5) using a knurled screw (5.1)	 Set to the max. permissible spread value (B) before disassembling the piston ring (1, 2, 3).	*BE03.10-N-1001-05I
			*000589373700
5	Remove piston rings (1, 2, 3) in the order from top to bottom		*000589373700
	Checking
6	Check piston rings (1, 2, 3) for chippings on the coating	 If damaged: 
		Replace piston rings (1, 2, 3).
7	Measure piston ring gap clearance of piston rings (1, 2, 3)		AR03.10-W-7311-02C
			*BE03.10-N-1002-05I
			*WH58.30-Z-1004-12A
	Install
8	Adjust pliers (5) using a knurled screw (5.1)	 Set to the max. permissible spread value (B) before piston ring installation (1, 2, 3).	*BE03.10-N-1001-05I
			*000589373700
9	Insert piston ring spring expander (3.1) (bevel-edged ring with spring expander) (3) into the lower groove of the piston (4)
10	Install piston ring (bevel-edged ring with spring expander) (3) using pliers (5)	 Note installation position; the spring expander offset (A) from the coil spring end gap (arrow) to the piston ring end gap must be offset by about 180°.
			*000589373700
11	Install piston rings (1, 2) in the sequence from below to above using pliers (5)	 Pay attention to installation position. Marking "TOP" must point toward piston crown.
			*000589373700
12	Check piston rings (1, 2, 3) for chippings on the coating	 If damaged: 
		Replace piston rings (1, 2, 3).
13	Install piston (4)		AR03.10-W-7021C

Check values for piston rings

Number	Designation				Engine 457.9


BE03.10-N-1001-05I	Spread value of piston ring		max.	mm	43
BE03.10-N-1002-05I	Piston ring end clearance	Groove I	When new	mm	0.45...0.60
		Keystone ring	Service limit	mm	1,0
		Groove II	When new	mm	0.40...0.55
		Taper-faced ring with inside race	Service limit	mm	1,0
		Groove III	When new	mm	0.40...0.55
		Bevel-edge ring with garter spring	Service limit	mm	0,8

000 589 37 37 00

Pliers

Commercially available tools

Number	Designation
WH58.30-Z-1004-12A	Feeler gauge

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