Test coolant thermostat - AR20.10-P-2455GZS (ML63 AMG)

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ENGINE 156 in MODEL 164, 251

Fig 1: Identifying Coolant Thermostat And Valve

Courtesy of MERCEDES-BENZ OF NORTH AMERICA.

	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
1	Remove coolant thermostat (1)	Installation: Install new sealing ring. The coolant thermostat (1) must not be removed from the housing. Otherwise it will be destroyed. The housing is supplied together with a coolant thermostat (1) for repair purposes.	AR20.10-P-2460GZS
	Checking
2	Heat coolant thermostat (1)	Suspend coolant thermostat (1) from a wire in a vessel filled with water and heat water. For heating up under no circumstance use a welding torch or a soldering torch, otherwise sudden heat penetration modifies the metal structure!
3	Measure temperature of water	The heating-up rate should be not more than 1 to 2°C / minute from about 8°C below start of opening of coolant thermostat (1).
		Digital temperature measuring unit	*WH58.30-Z-1002-08A
4	Heat water to the fully open temperature of thermostat (2) and then measure stroke of valve (2)	If the check values are not achieved, replace coolant thermostat (1).
		Start of opening	*BE20.10-P-1001-02D
		Minimum stroke	*BE20.10-P-1002-02D
5	Install in the reverse order
6	Inspect cooling system for leaks		AR20.00-P-1010GZS
	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
7	Conduct engine test run and check engine for leaks	In the event of oil loss determine and eliminate cause, otherwise malfunctions, transmission damage, and serious environmental pollution may occur.

COOLANT THERMOSTAT

Number	Designation			Engine 156
BE20.10-P-1001-02D	Start of opening	Conventional	°C	98 to 102
BE20.10-P-1001-02D	Start of opening	Electrical	°C	65
BE20.10-P-1002-02D	Minimum stroke	Conventional	°C	115
		Electrical	°C	100
		Conventional	mm	5
		Electrical	mm	8

COMMERCIALLY AVAILABLE TOOLS

Number	Designation
WH58.30-Z-1002-08A	Digital temperature measuring instrument (measuring range -20° to +70°)