* Water pump: A failing water pump seal is a common cause of coolant leaks, especially around the back of the engine where the pump is often located. When the seal wears, coolant can leak out.
* Intake manifold gasket: If the intake manifold gasket is leaking, coolant can seep out from the back of the engine, particularly if the gasket is damaged near the rear of the manifold. This is more likely if you're experiencing other symptoms like rough running or loss of power.
* Head gasket: This is a more serious issue. A blown head gasket can allow coolant to mix with oil (causing milky oil) or leak externally from various points, including the back of the engine. This often comes with other symptoms like overheating, white smoke from the exhaust, or loss of compression.
* Coolant hoses: While less likely to be at the very back, a cracked or deteriorated hose, particularly one connected to the heater core or a component near the rear of the engine, could be the source.
* Cracked engine block or cylinder head: A crack in the engine block or cylinder head is a severe problem and would usually result in a substantial coolant leak. This is less common but possible.
* Thermostat housing: A leak around the thermostat housing is possible, especially if the gasket is damaged or the housing is cracked.
To diagnose the problem accurately, you (or a mechanic) will need to:
1. Visually inspect the engine: Carefully look for any visible signs of coolant leakage. Pay close attention to the areas mentioned above. A flashlight and perhaps even a mirror to see hard-to-reach places will be helpful.
2. Pressure test the cooling system: This involves pressurizing the cooling system to check for leaks. This is the most reliable way to pinpoint the source of the leak.
3. Check the oil for coolant contamination: Milky or foamy oil strongly suggests a head gasket problem.
4. Check the coolant for oil contamination: Oil in the coolant indicates a problem with the head gasket or possibly a cracked block.
Because pinpointing the exact location of the leak from the back of the engine requires a visual inspection and likely a pressure test, it's strongly recommended you take your car to a qualified mechanic. Attempting repairs without proper diagnosis could worsen the problem. Ignoring a coolant leak can lead to serious engine damage.
