Leak Testing
TESTING FOR LEAKS
ULTRAVIOLET LIGHT METHOD
A leak detection additive that is added to the cooling system is available through the parts department. The additive is highly visible under ultraviolet light (black light) (1). Pour one ounce of additive into cooling system. Place the heater control unit in the HEAT position. Start and operate the engine until the radiator upper hose is warm to the touch. Aim the commercially available black light tool at components to be checked. If leaks are present, the black light will cause the additive to glow a bright green color.
The black light can be used in conjunction with a pressure tester to determine if any external leaks exist.
PRESSURE TESTER METHOD
Make sure the engine is at normal operating temperature. If the cause of coolant loss is not identified while the engine is warm, recheck the system when it is cold.
WARNING: Hot, pressurized coolant can cause injury by scalding.
Carefully remove the radiator pressure cap from the filler neck and check the coolant level. Push down on cap to disengage it from the stop tabs. Wipe the inside of filler neck and examine the lower inside sealing seat for nicks, cracks, paint, dirt and solder residue. Inspect the radiator-to-reserve/overflow tank hose for internal obstructions. Insert a wire through the hose to make sure it is not obstructed.
Inspect the cams on the outside of the filler neck. If the cams are damaged, seating of the pressure cap valve and tester seal will be affected.
Attach pressure tester (7700 or equivalent) (1) to radiator filler neck.
Operate tester pump to apply 124.1 kPa (18 psi) pressure to system. If hoses enlarge excessively or bulge while testing, replace as necessary. Observe the gauge pointer and determine the condition of the cooling system according to the following criteria:
Holds Steady: If the pointer remains steady for two minutes, serious coolant leaks are not present in the system. However, there could be an internal leak that does not appear with normal system test pressure. If it is certain that coolant is being lost and leaks cannot be detected, inspect for interior leakage or perform Internal Leakage Test. Refer to INTERNAL LEAKAGE INSPECTION.
Drops Slowly: Indicates a small leak or seepage is occurring. Examine all connections for seepage or slight leakage with a flashlight. Inspect radiator, hoses, gasket edges and heater. Repair leak holes and inspect system again with pressure applied.
Drops Quickly: Indicates that serious leakage is occurring. Examine system for external leakage. If leaks are not visible, inspect for internal leakage. Large radiator leak holes should be repaired by a reputable radiator repair shop.
INTERNAL LEAKAGE INSPECTION
Remove engine oil pan drain plug and drain a small amount of engine oil. If coolant is present in the pan, it will drain first because it is heavier than oil. An alternative method is to operate the engine for a short period to churn the oil. After this is done, remove engine dipstick and inspect for water globules. Also inspect the transmission dipstick for water globules and the transmission fluid cooler for leakage.
WARNING: With radiator pressure tester tool installed on radiator, do not allow pressure to exceed 145 kpa (21 psi). Pressure will build up quickly if a combustion leak is present. To release pressure, rock tester from side to side. When removing tester, do not turn tester more than 1/2 turn if system is under pressure.
Operate the engine without the pressure cap on the radiator until the thermostat opens. Attach a Pressure Tester to filler neck. If pressure builds up quickly it indicates a combustion leak exists. This is usually the result of a cylinder head gasket leak or crack in engine. Repair as necessary.
If there is no immediate pressure increase, pump the Pressure Tester. Do this until indicated pressure is within system range of 124.1 kPa (18 psi). Fluctuation of gauge pointer indicates compression or combustion leakage into the cooling system.
Because the vehicle is equipped with a catalytic converter, do not remove spark plug cables or short out cylinders to isolate the compression leak.
If the needle on the dial of the pressure tester does not fluctuate, accelerate engine a few times to check for an abnormal amount of coolant or steam, emitting from the exhaust pipe. Coolant or steam from the exhaust pipe may indicate a faulty cylinder head gasket, cracked engine cylinder block or cylinder head.
A convenient check for exhaust gas leakage into the cooling system is provided by a commercially available Block Leak Check tool. Follow the manufacturer's instructions when using this product.
COMBUSTION LEAKAGE TEST - WITHOUT PRESSURE TESTER
DO NOT WASTEreusable coolant. If the solution is clean, drain the coolant into a clean container for reuse.
WARNING: Do not remove cylinder block drain plugs or loosen radiator draincock with system hot and under pressure. Serious burns from coolant can occur.
Drain sufficient coolant to allow thermostat removal, Engine Coolant Thermostat - Removal. Remove the accessory drive belt, Serpentine Accessory Drive Belt - Removal.
Add coolant to the radiator to bring the level to within 6.3 mm (1/4 in) of the top of the thermostat housing.
CAUTION: Avoid overheating. Do not operate engine for an excessive period of time. Open draincock immediately after test to eliminate boil over.
Start the engine and accelerate rapidly three times, to approximately 3000 rpm while observing coolant. If internal engine combustion gases are leaking into the cooling system, bubbles will appear in the coolant. If bubbles do not appear, internal combustion gas leakage is not present.