All VW's are filled with a mixture of water and special phosphate-free antifreeze at the factory. The antifreeze has corrosion inhibitors that prevent frost, the formation of chalk, and also raise the boiling point of the water. Volkswagen recommends using VW phosphate free antifreeze/coolant part number ZVW237 when replacing or adding coolant. Most brand name antifreeze manufacturers recommend a 50/50 antifreeze-to-water mixture for maximum protection from freezing and overheating. A hydrometer is available at most parts stores that checks the freeze protection of the coolant, much like a battery hydrometer. Don't use a battery hydrometer, though; it's not calibrated for coolant and would no longer be usable for batteries. When deciding on the antifreeze/water mixture for refilling or adding to the system, follow the manufacturer's instructions on the container.
If you intend to switch from an ethylene based antifreeze to a propylene based antifreeze, the cooling system must be flushed several times with clean water. These two different types of antifreeze are not compatible and cannot be mixed together; doing so will neutralize the special properties of a propylene based antifreeze.
See Figures 1, 2, 3 and 4
Make it a habit to periodically check the coolant level in the radiator. Ideally, this should be performed when the engine is cold. When removing the pressure cap, loosen it slightly first. If the coolant begins to boil, tighten the cap again and wait for the engine to cool down. On some models, a gauge plate inside or outside the radiator filler neck aids in level checking. The coolant should be maintained at the bottom of the plate.
Some models are equipped with a coolant reservoir. The reservoir is translucent and can be checked without removing the cap. Some later models have a coolant expansion tank and no radiator cap. The reservoir has low and high level marks. The coolant must be between the two marks when the engine is cold and slightly above the high mark at normal operating temperature. On models with an expansion tank and no radiator cap, observe the same cautions when removing the pressure cap from the expansion tank as with a radiator cap. Wrap it with a heavy rag and open the cap slowly to release the pressure from the cooling system.
Some models are equipped with a light on the dash that flashes until the coolant level is filled to the normal level.
DRAIN AND REFILL
The thermostat must be removed to drain the system. Before draining the coolant, purchase a new thermostat O-ring.
- Raise and safely support the front of the vehicle on jackstands.
- Place a large drain pan under the engine.
- On some early models, there is a petcock at the bottom of the radiator. Loosen it to drain the radiator.
- Loosen the thermostat housing bolts (refer to Engine & Engine Overhaul ). When they are both loose and the housing is pulled slightly away from the water pump assembly, coolant will start to flow.
- When the coolant stops flowing, there may still be some in the radiator or in the cylinder block. Keep the drain pan in place and remove the thermostat housing from the water pump assembly. It's not necessary to disconnect the lower radiator hose.
- Remove the thermostat and the radiator/reservoir cap to drain the rest of the coolant.
- Clean and dry the thermostat housing and the rubber O-ring. Examine the O-ring for cracks or damage, replace as necessary.
- Install the thermostat into the water pump housing on the engine, then fit the O-ring into place.
- Install the thermostat housing and tighten the bolts evenly. Torque the bolts to 87 inch lbs. (10 Nm). Do not overtorque these bolts or the housing may break.
- Loosen the upper radiator hose and begin filling the system through the coolant reservoir or radiator. Loosening the upper hose will allow the air to escape and speed the processes.
- When the system will not take any more coolant, tighten the hose and start the engine. Watch for leaks and add more coolant as required. Don't run the engine too long with the reservoir cap removed or it will boil over.
FLUSHING AND CLEANING THE SYSTEM
The cooling system should be drained and refilled with new coolant at least every 30,000 miles (48,000 km) or 24 months. Other than this service, Volkswagen does not recommend any special cooling system flushing. If you decide to do so, use a system flush made for use with aluminum cooling system components and follow the instructions on the package.