Remove/install chain tensioner, with thread M22 X 1.5 - AR05.10-P-7800GZG (ML350, ML550, GL450, GL550)

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ENGINES 272, 273 in MODEL 164, 251

Chain tensioner with thread M22 X 1.5

Fig 1: Identifying Chain Tensioner Components (1 Of 2)

Courtesy of MERCEDES-BENZ USA

Fig 2: Identifying Chain Tensioner Components (2 Of 2)

Courtesy of MERCEDES-BENZ USA

	Removing
1	Rotate engine at crankshaft center bolt in direction of rotation of the engine to a 40° crankshaft angle after ignition TDC		Fig 3
2	Detach connector for circuit 61 (D+) from alternator and remove alternator from timing case cover (2)	The alternator remains with its attached line for circuit 30 (B+) in the engine compartment. See ↓ Remove/install alternator:	AR15.40-P-5032GZA
3	Remove chain tensioner (1) from timing case cover (2)
	Installing
4	Screw new chain tensioner (1) into timing case cover (2) and tightened to prescribed torque	Replace chain tensioner (1). The previously installed chain tensioner (1) must not be reinstalled since, on removal of pressure bolt (1a), it is pressed into the end position and the locking device of the pressure bolt prevents its return stroke. This would overstretch the timing chain on reinstalling.
			*BA05.10-P-1008-01B
5	Remove cap (3)
6	Turn engine at center bolt on the crankshaft with the prescribed torque against the direction of engine rotation (arrow) while counterholding the left exhaust camshaft (4) at the rear with a Torx wrench	This unlocks the chain tensioner (1).
			*BA05.10-P-1009-01B
7	Rotate engine at the center Bolt, the crankshaft in the direction of rotation of the engine through a 90° crank angle.	The thrust pin (1a) for the chain tensioner (1) will be pushed out and tensions the timing chain.
8	Install end cover (3)
9	Install alternator		AR15.40-P-5032GZA
	Risk of accident caused by vehicle starting off by itself when engine is running. Risk of injury caused by contusions and burns during starting procedure or when working near the running engine	Secure vehicle to prevent it from moving by itself. Wear closed and snug-fitting work clothes. Do not grasp hot or rotating parts.	AS00.00-Z-0005-01A
10	Carry out an engine test run and check the engine for leaks

TIMING CHAIN, CHAIN TENSIONER

Number	Designation			Engine 272	Engine 273
BA05.10-P-1008-01B	Chain tensioner to timing case	M22 x 1.5	Nm	70	70
BA05.10-P-1009-01B	Torque to unlock chain tensioner		Nm	70	70

Fig 3: Identifying Wrench Socket (001 589 65 09 00)

Courtesy of MERCEDES-BENZ USA