The engine cooling system is made up of a set of components that circulate coolant through the engine to keep it from overheating. If one of the components fails, it can result in coolant leaking out.
If you have a problem with the coolant level dropping, but no signs of an external leak, the issue may be an internal engine leak. This type of leak may be due to a leaking intake manifold gasket, head gasket, or oil cooler. A shop will need to conduct various tests to find these types of leaks.
Engine coolant leaks are typical for all vehicles, old and new, without regard to mileage. Driving conditions, driving style, age of the car, and lack of maintenance can all make coolant leaks more likely.
Maintaining the cooling system will dramatically reduce the number of leaks the vehicle will have over time.
How are coolant leaks diagnosed?
The first thing mechanics check when dealing with coolant leaks is the radiator cap. This part keeps the cooling system properly pressurized, so when it fails, problems ensue.
After the radiator cap, the vehicle will be inspected for obvious leaks, damage to cooling system components, and contamination in the coolant reservoir. If contamination from combustion exists in the cooling system, the engine cylinder block, cylinder head and head gasket are suspected.
If no leak is noticed, and there's no obvious sign of damage, the technician will apply a pressure tester and UV dye to the cooling system, causing the leak to become visible with a UV flashlight.
How is a coolant leak fixed?
Repairing a coolant leak typically requires draining the engine coolant from the entire system, removing the faulty part, and either cleaning or replacing that component before reinstallation.
Internal leaks tend to mean expensive repairs — a new head gasket or a new or refurbished engine being the most likely. Most often, though, repairing a leak involves a simple hose replacement and coolant flush.
A pressure check of the cooling system should be performed to determine where a coolant leak is originating. After repairs, the system should be pressure tested again to verify that the repair is successful.
When a coolant hose is found to be leaking due to age and/or condition, you should replace all of the coolant hoses in order to prevent failure.
After the cooling system has been serviced or repaired, it's important to verify that the system is not leaking, the radiator fans are operating properly, and all air bubbles and air pockets are bled from the cooling system.
