Cooling system leaks, if left unchecked, can cause serious damage to the engine of your VW Passat. That's why it's critical to periodically check for any visible leakage and to monitor your engine's coolant level, even if there aren't any outward signs of leakage. This procedure is easy, only takes a few minutes and could save you money in auto mechanics charges.
Move your VW Passat from its normal parking spot and check the area beneath the engine. Because engine coolant is a vibrant color, usually green or orange, any leakage should be easy to see on the ground. However, just because there aren't any signs of leakage from the underneath of the VW Passat, doesn't mean there's nothing to worry about. There can be leakage that just didn't make it to the ground.
Park the VW Passat and open the hood. Inspect all the hoses that connect the radiator to the engine and the engine to the heater core nearest the windshield of the VW Passat. Look for any bulging, cracking or splitting and you should be able to see the leaking coolant or at least signs of it, if the hoses are the cause. However, there are times when a pinhole or pinch leak only surface when the hoses are warm.
Examine the water pump and the shaft seal. The water pump is behind the engine fan and attached to the engine by the shaft seal. If you notice any discoloration or corrosion in this area, this is a sure sign of a cooling system leak. If it's the water pump, then most likely you'll need to replace it.
Check all visible areas of the radiator with a flashlight for signs of leakage. Again, these signs are discoloration, corrosion or visibly leaking fluid. Inspect the underside of the radiator carefully because rocks and other road debris can damage the radiator during the normal operation.
Turn the radiator cap one full turn and step back for a minute. Then, remove the radiator cap completely. Be very careful when doing this, as the internal pressure can cause a coolant eruption, which can severely burn anyone in the area.
Add more coolant to the radiator until it's within an inch from overflowing. Then, start the VW Passat with the heater set to high. Allow the car to run in this manner for about 15 minutes.
Shut off the engine and check all of the previously mentioned auto parts for a possible leak. If the coolant level continues to drop with no visible signs of leaking, then the problem may be internal. In this case, take the VW Passat to cooling system specialist for further diagnostic testing.
