How to Diagnose a Leak inside Your Car

There’s no such thing as an insignificant leak. Leaks always get bigger over time. Paying attention to damp spots or small puddles inside your car can save you money in the long run. Visit your mechanic after determining what kind of leak your car has. Wetness inside your car can come from a few different sources.
Instructions
1. If there is a clear, slippery liquid under the seat, check your brake-fluid levels to find out which reservoir is leaking. The leak indicates that brake fluid is spilling from either the brake master cylinder or the clutch master cylinder.
2. If a stick, green, sweet-smelling fluid is leaking under the passenger’s feet, check the heater core or heater hose for a leak. This is a coolant leak of the cooling system.
3. If the inside of the car smells of exhaust, look for a broken tailpipe or a worn or improperly seated rubber seal around the hatchback. This smell means there is likely a leak in the exhaust system.
4. To find a rain leak, close the doors and windows tightly on a dry day and have someone hose down the car while you sit inside and look for signs of water entering. It may take a while, but it’s the best way to find rain leak.
5. If there’s water under the dashboard when it’s not raining, see if water is collecting in the air conditioner duct. Sometimes the drain tube is clogged with debris causing the duct to drip.
Whether working on cars is a hobby or a cost-driven necessity, most DIYers and backyard mechanics are better off with inexpensive alternatives to expensive professional tools. There are some good tools that can interface with your computer, phone, or tablet.