Remove/install coolant thermostat - AR20.10-P-2460GZA (ML350, ML550, GL450, GL550)

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ENGINE 272, 273 in MODEL 164, 251

Fig 1: Identifying Coolant Thermostat Components

Courtesy of MERCEDES-BENZ OF NORTH AMERICA.

Shown on engine 272

	Remove/install
	Risk of injury to skin and eyes caused by scalding from contact with hot coolant spray. Risk of poisoning caused by swallowing coolant.	Do not open cooling system unless coolant temperature is below 90°C. Open cap slowly and release the pressure. Do not pour coolant into beverage containers. Wear protective gloves, protective clothing and safety glasses.	AS20.00-Z-0001-01A
	Notes on coolant		AH20.00-N-2080-01A
	Information on preventing damage to electronic components due to electrostatic discharge		AH54.00-P-0001-01A
1	Switch off ignition and remove the transmitter key from the EIS [EZS] control unit	On vehicles with code (889) Keyless Go: Press keyless go start/stop button repeatedly until ignition is switched off. Remove transmitter key from vehicle and store it in a location beyond its transmission range (at least 2 m).
2	Drain coolant at radiator		AR20.00-P-1142GZC
3	Detach upper coolant hose (1) from coolant thermostat housing (2) and place it on the side	Installation: Replace O-ring (1a).	AR09.41-P-1311-01AL
4	Remove poly-V belt and guide pulley (3)		AR13.20-P-0001GZA
5	Unlatch electrical connector at three-disk thermostat valve (Y110) and disconnect
6	Remove bolts (2a, 2 pieces)		*BA20.10-P-1003-01U
7	Pull out coolant thermostat housing (2) with coolant thermostat from timing case cover	The coolant thermostat and coolant thermostat housing (2) are a single unit. The coolant thermostat must not be taken out of coolant thermostat housing (2) as it can get damaged in the process. Installation: Replace gasket (2b) and O-ring (2c).
8	Install in the reverse order
	Checking
	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 engine as it is running	Secure vehicle to prevent it from moving by itself. Wear closed and snug-fitting work clothes. Do not touch hot or rotating parts.	AS00.00-Z-0005-01A
9	Conduct engine test run and check the engine for leaks
10	Connect STAR DIAGNOSIS and read fault memory	Stored faults which may be caused by disconnecting cables or by simulation during test operations, must be erased in the fault memory after completing the work.	AD00.00-P-2000-04A

COOLANT PUMP, COOLANT THERMOSTAT

Number	Designation		Engine 272	Engine 273
BA20.10-P-1003-01U	Bolt, coolant thermostat housing at timing case cover	Nm	25	25