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radiator hose
Check the hoses entering and exiting the radiator for antifreeze (coolant) leaks

driveshaft (CV axle)
Check the area where the driveshafts (cv axles) enter the gearbox for leaks

check brake lines for leaks
Check the brake lines entering the calipers for leaking brake fluid

power steering fluid resevoir
Power steering fluid can be leaking from the pressurized metal connections on the steering rack

How to identify vehicle leaks

TIPS - When trying to track down leaks it can help to wipe down the engine to get rid of excess dirt and debris. It can also help to put a large white sheet of paper under the vehicle overnight to highlight the location of the leak - and also the quantity of liquid which is emerging.
When you start seeing random Jackson Pollock-like bits of artwork mysteriously appearing on your garage floor or driveway it's time to start looking for vehicle leaks. There's a number of different fluids which can be seeping out, and they can come from a wide variety of locations. However there are a few problem areas and weak spots which are a good place to start looking.

Sometimes it can be hard to track down the source of a leak, especially if the engine is dirty, as most are. Always check around - and most importantly above - the area where you see fluid deposits, as the liquid may have leaked from a different area, but pooled in a more visible location.

Here's some good places to start looking, and a guide on what the liquid might be.

Sump Oil - Engine oil may be leaking out of the drain plug hole if the plug was incorrectly fitted or the gasket has failed. Or it can be leaking from the sump gasket itself. Both of these leaks are very low down on the engine so will often not leave oil pooling anywhere on the engine - just the floor. To check this location you'll have to get under the vehicle and have a look around. Taking a small flashlight under there will be helpful.

Oil from the Filter
- Sometimes oil can be leaking from the oil filter if it has been incorrectly fitted or has become loose over time. The gasket may also have been damaged during installation. If this is the source of the leak it's usually very easy to fix. To check this area, locate the oil filter and look closely around the point at which it screws into the engine block. If possible wipe a clean cloth around the base of the filter and look for fresh oil runs or deposits.

Transmission Fluid / Gearbox Oil
- While engine oil is usually the culprit of oily spots, it can also be gearbox oil. If gearbox oil is the offending liquid, it usually finds its way out though failed seals at the inboard ends of the driveshafts (CV axles). Basically look around the area where the driveshafts enter the gearbox on both sides and check for runs from this point. Also check the underneath of the transmission/gearbox to see if any other gaskets may have failed.

Antifreeze (Coolant)
- Antifreeze leaks are generally relatively easy to identify due to the distinctive color - almost always either red or green - and the watery consistency of the liquid. Leaking coolant often leaves white, powdery crystalline deposits in the area, or areas, it is leaking from. Weak spots in the cooling system which are a good place to start the leak hunt are; around the water pump (check the pump's bearings and gasket), the hoses entering and exiting the radiator, around the thermostat housing, and the radiator itself.

Brake Fluid - Brake fluid - on a dirty vehicle - can look very similar to leaking engine oil. The key difference is the areas in which the leaks will be found. Any leak found near the wheel will almost certainly be brake fluid. Check the hoses entering the brake calipers and brake master and slave cylinders.

Power Steering Fluid
- Power steering fluid is a hydraulic fluid which may leak out of the pipe connections on the steering rack. It can leak from other areas, but this is a good place to start looking.

Fuel Leak - Fuel leaks are perhaps the most dangerous type of vehicle leak. Fuel leaks generally make themselves known due to the strong and distinctive odor. Fuel leaks, especially in the engine bay can lead to a fire resulting in loss of the vehicle. If a fuel leak is expected do not drive the vehicle - have it towed immediately to a garage where a professionally can perform a repair.

Any vehicle leak can turn into an expensive repair if it is not repaired quickly. The liquids in a vehicle's engine are essential to its operation. Low levels of oil or coolant can lead to overheating and seizing of the engine - usually meaning a whole new engine is needed. And it could have all been avoided for the price of a five dollar gasket and 30 minutes of work - if you're lucky!

See also:
All Tutorials
How To Check Your Oil
How To Identify Vehicle Leaks
Basic Tire Maintenance
Take 10 Years Off Your Car's Appearance
How to Perform a Heel-and-Toe Downshift
Left-Foot Braking
Driving on Snow and Ice
What is Torque?
What is a 'Monocoque'?
What are Superchargers?
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