Warning: Wait until the engine is cold before starting this proc- edure. Do not allow antifreeze to come in contact with your skin, or with the painted surfaces of the vehicle. Rinse off spills immediately with plenty of water. Never leave antifreeze lying around in an open container, or in a puddle in the driveway or on the garage floor. Children and pets are attracted by its sweet smell, but antifreeze can be fatal if ingested.
Cooling system draining
After allowing the engine to cool completely, cover the pressure cap with a wad of rag, and slowly turn the cap anti‑clockwise to relieve the pressure in the cooling system (a hissing sound will normally be heard). Wait until any pressure remaining in the system is released, then continue to turn the cap until it can be removed
Removing the pressure cap from the coolant expansion tank
Position a suitable container beneath the radiator, and then slacken the drain plug on the bottom left-hand corner of the radiator. Allow the coolant to drain into the container
Remove the radiator drain plug
Reposition the container so that it lies beneath the engine block drain plug, which is located on the side of the cylinder block
. (Certain engines are fitted with a drain plug with an integral nozzle, to which a length of rubber hose can be connected.) Open the drain plug and allow the coolant to drain into the container.
Cylinder block drain plug
Once all the coolant has drained, remove the drain hoses and close the cylinder block and radiator drain plugs.
Cooling system flushing
If coolant renewal has been neglected, or if the antifreeze mixture has become diluted, then in time, the cooling system may gradually lose efficiency, as the coolant passages become restricted due to rust, scale deposits, and other sediment. The cooling system efficiency can be restored by flushing the system clean.
The radiator should be flushed independently of the engine, to avoid unnecessary contamination.
To flush the radiator disconnect the top and bottom hoses and any other relevant hoses from the radiator.
Insert a garden hose into the radiator top inlet. Direct a flow of clean water through the radiator, and continue flushing until clean water emerges from the radiator bottom outlet.
If after a reasonable period, the water still does not run clear, the radiator can be flushed with a good proprietary cooling system cleaning agent. It is important that the manufacturer’s instructions are followed carefully. If the contamination is particularly bad, insert the hose in the radiator bottom outlet, and reverse-flush the radiator.
To flush the engine, remove the thermostat, and then temporarily refit the thermostat cover. Adjust the heater control to the maximum setting.
With the top and bottom hoses disconnected from the radiator, insert a garden hose into the radiator top hose. Direct a clean flow of water through the engine, and continue flushing until clean water emerges from the radiator bottom hose.
On completion of flushing, refit the thermostat and reconnect the hoses.
Cooling system refilling
Before attempting to fill the cooling system, make sure that all hoses and clips are in good condition, and that the clips are tight. Note that an antifreeze mixture must be used all year round, to prevent corrosion of the engine components (see following sub-Section).
|Coolant quantity (all models)
||MB 325.0 000 989 08 25 or 000 989 21 25
Remove the pressure cap, and fill the system by slowly pouring the coolant into the expansion tank to prevent airlocks from forming.
If the coolant is being renewed, begin by pouring in a couple of litres of water, followed by the correct quantity of antifreeze, then top-up with more water.
Once the level in the expansion tank/header tank starts to rise, squeeze the radiator top and bottom hoses to help expel any trapped air in the system. Once all the air is expelled, top-up the coolant level to the MAX mark. Refit the pressure cap securely.
Where applicable, unscrew the plug from the coolant sensor housing, on the upper surface of the cylinder head. As soon as coolant starts to flow out, refit the plug and tighten it. If none flows out, pour coolant into the hole vacated by the plug until it begins to flow back out. Refit the plug and tighten it securely. This removes any airlocks in the cooling system that might inhibit the operation of the coolant sensor(s).
Start the engine and run it until the thermostat opens – the radiator top hose will begin to heat up as coolant flows through it of the radiator when this happens.
Check for leaks, particularly around disturbed components. Check the coolant level in the expansion tank/header tank, and top-up if necessary. Note that the system must be cold before an accurate level is indicated. If the pressure cap is removed while the engine is still warm, cover the cap with a thick cloth, and unscrew the cap slowly to gradually relieve the system pressure (a hissing sound will normally be heard). Wait until any pressure remaining in the system is released, then continue to turn the cap until it can be removed.
The antifreeze should always be renewed at the specified intervals. This is necessary not only to maintain the antifreeze properties, but also to prevent corrosion, which would otherwise occur as the corrosion inhibitors become progressively less effective.
Always use an ethylene glycol based antifreeze, which is suitable for use in mixed-metal cooling systems.
Before adding antifreeze, the cooling system should be completely drained, preferably flushed, and all hoses checked for condition and security.
After filling with antifreeze, a label should be attached to the expansion tank or header tank, stating the type and concentration of antifreeze used, and the date installed. Any subsequent topping-up should be made with the same type and concentration of antifreeze.
Do not use engine antifreeze in the windscreen/tailgate washer system, as it will cause damage to the vehicle paintwork. A screenwash additive should be added to the washer system in the quantities stated on the bottle.