Checking the tightness of the hoses and fluid leakage (VW Golf 4)

Cooling system leaks are usually detected by a white or rust-colored coating in the area adjacent to the leak.

Carefully inspect the radiator and coolant hoses along their entire length. Replace any hoses that are cracked, torn, or showing signs of wear. Cracks are easier to spot if the hose is pinched. Pay particular attention to the clamps that attach the hoses to the cooling system components. Hose clamps that have been tightened too much can cause the hose to rupture or puncture, resulting in leaks in the cooling system. Inspect all hoses and hose connection surfaces for leaks. If any leaking problems of this nature are found, replace that component or gasket.

Fuel leaks are difficult to pinpoint until the leak is significant and therefore easily visible. Fuel tends to evaporate quickly once it comes into contact with air, especially in a hot engine bay. Small droplets may disappear before you can pinpoint the leak. If you suspect a fuel leak in the engine bay area, then cool the engine and run it while it is cold with the hood open. Metal objects tend to shrink when cold, rubber hoses tend to loosen, so any leaks will be more obvious as the engine warms up from cold starting.

If there are signs that there is a leak of some kind of fluid, but you cannot identify the type of fluid or the exact source, then you should leave the car for a long time and put a large piece of paper or rag under the car. This will help to find the place of the leak and also help to identify the leaking fluid by color. But keep in mind that some leaks may only appear when the engine is running.

A leak in the vacuum hose means that air is being sucked into the hose (but it doesn't come out of the hose), and this makes the leak very difficult to detect. The detection method is to use an old vacuum hose as a kind of stethoscope. Hold one end of the hose close to your ear (but not in the ear), and use the other end to probe the area around the suspected leak. When the end of the hose is directly over the leak, a hissing sound will be clearly audible through the hose. Avoid contact with hot or moving parts, as the engine must be running when checking.