Set basic position of camshafts - AR05.20-P-6020MMB

ENGINE 157, 276, 278 in MODEL 221 

ENGINE 157, 278 in MODEL 216 

Shown on engine 278 

Fig 1: Identifying Camshafts Marking - Shown On Engine 278

Courtesy of MERCEDES-BENZ USA

	Risk of injury  . Moving parts can pinch, crush or, in extreme cases even sever extremities.	No parts of the body or limbs should be within the operating range of the mechanism when moving components.	AS00.00-Z-0009-01A
	Remove
1	Remove centrifuge	ENGINE 276	AR01.20-P-2100MMA
		ENGINE 157, 278	AR01.20-P-2100MMB
2	Remove cylinder head covers	Engine 276 - right cylinder head cover	AR01.20-P-5012MMA
		Engine 276 - left cylinder head cover	AR01.20-P-5013MMA
		Engine 157, 278 - right cylinder head cover	AR01.20-P-5012MMB
		Engine 157, 278 - left cylinder head cover	AR01.20-P-5013MMB
3	Check segmented discs (4) for marking (4m)
4	Remove camshafts (1)	If marking (4m) is not present on the segmented discs (4)
			AR05.20-P-6992MM
5	Attach marking (4m) to the segmented discs (4)	If marking (4m) is not present on the segmented discs (4)
			AR05.20-P-6292-04MM
		Template	Figure
6	Install camshafts (1)	If marking (4m) is not present on the segmented discs (4)
			AR05.20-P-6992MM
7	Mount hold-down tool (01) on camshafts (1)	Tie-down set	Figure
8	Rotate engine at crankshaft center bolt in direction of engine rotation to a 40° crank angle (CKA) after top dead center (TDC) on cylinder 1 (ignition TDC)		AR05.10-P-7620-04MM
		After performing repair work on crank assembly ensure that this stands at 40° after ignition TDC. If the crank assembly should stand at 40° after overlap TDC for assembly, all camshafts (1) have a wrong position of about a tooth for the basic setting. If the crankshaft is turned with the secondary chains removed, this may only take place in 720° steps in order to again come to the correct ignition TDC on the crank assembly.
9	Remove both chain tensioners	ENGINE 276 in MODEL 221	AR05.10-P-7800MMA
		ENGINE 157, 278 in MODEL 216, 221 For removed cylinder head covers both chain tensioners can be removed for a 40  ° crank angle (CKA) after top dead center (TDC) on cylinder 1 (ignition TDC). To remove the RH chain tensioner the tensioning rail should be relieved by an assistant by turning the exhaust camshaft.	AR05.10-P-7800MMB
10	Remove camshaft positioner (3) for exhaust camshaft on right cylinder head		AR05.20-P-7201MMB
		To loosen and tighten the control valve on the RH camshaft positioner (3), the exhaust camshaft (1) must be counterheld by a helper.
11	Remove timing chain (2) from camshaft positioners (3)	To relieve tensioning rail the camshafts (1) should be held by an assistant in the basic position.
12	Turn camshafts (1) into basic position	The camshafts (1) must be held in the basic position using a suitable tool by a helper.
	Check
13	Check timing chain (2) on left cylinder head for correct seating	Check whether the timing chain (2) lies on both camshaft positioners (3) and sits correctly in the toothings. If this is not the case: ↓ The respective camshaft (1) must be turned until the timing chain (2) lies on correctly.
14	Check camshafts (1) for correct installation position	Markings (4m) on segment discs (4) must be aligned with edges on both cylinder heads.
	Install
15	Mount camshaft positioner (3) for the right exhaust camshaft and in doing so lay the timing chain (2) on both camshaft positioners (3) of the right cylinder bank		AR05.20-P-7201MMB
		To tighten down the control valve on the right camshaft positioner (3) and to relieve tensioning rail, the camshafts (1) should be held by an assistant in their basic position.
16	Install both chain tensioners	ENGINE 276 in MODEL 221	AR05.10-P-7800MMA
		ENGINE 157, 278 in MODEL 216, 221 For removed cylinder head covers both chain tensioners can be removed for a 40  ° crank angle (CKA) after top dead center (TDC) on cylinder 1 (ignition TDC). To remove the RH chain tensioner the tensioning rail should be relieved by an assistant by turning the exhaust camshaft.	AR05.10-P-7800MMB
17	Crank engine at crankshaft center bolt in direction of engine rotation through about 720°.
18	Rotate engine at crankshaft center bolt in direction of engine rotation to a 40° crank angle after top dead center (TDC) on cylinder 1 (ignition TDC)		AR05.10-P-7620-04MM
		After performing repair work on crank assembly ensure that this stands at 40° after ignition TDC. If the crank assembly should stand at 40° after overlap TDC for assembly, all camshafts (1) have a wrong position of about a tooth for the basic setting. If the crankshaft is turned with the secondary chains removed, this may only take place in 720° steps in order to again come to the correct ignition TDC on the crank assembly.
19	Check engine valve timing	The engine must stand at a 40° crank angle (CKA) after top dead center (TDC) on cylinder 1 (ignition TDC) (marking on the belt pulley/vibration damper) and the markings (4m) on the segmented discs (4) must be flush with the edges on the cylinder heads. If the timing of the engine is not correct: ↓ Perform work procedure as of operation step 8 again.
20	Remove hold-down tool (01) on camshafts (1)	Tie-down set	Figure
21	Install cylinder head covers	Engine 276 - right cylinder head cover	AR01.20-P-5012MMA
		Engine 276 - left cylinder head cover	AR01.20-P-5013MMA
		Engine 157, 178 - right cylinder head cover	AR01.20-P-5012MMB
		Engine 157, 278 - left cylinder head cover	AR01.20-P-5013MMB
22	Install centrifuge	ENGINE 276	AR01.20-P-2100MMA
		ENGINE 157, 278	AR01.20-P-2100MMB
	Risk of accident  from vehicle starting off by itself when engine running. Risk of injury  (bruises and burns) resulting from working on the engine while it is being started or when it is running.	Secure vehicle to prevent it from starting off by itself. Wear closed and snug-fitting work clothes. Do not touch hot or rotating parts.	AS00.00-Z-0005-01A
23	Carry out an engine test run, checking the engine for proper operation and leaktightness

Fig 2: Identifying Tie-Down Set (276 589 01 40 00)

Courtesy of MERCEDES-BENZ USA

Fig 3: Identifying Template (278 589 00 23 00)

Courtesy of MERCEDES-BENZ USA