Chevrolet Cobalt Service & Repair Manual: Cooling System Leak Test

A visual inspection must always be performed to confirm the presence of aftermarket components, potential collision damage, or areas of concern.
Always clean all external cooling system components, hoses and lines before starting the inspection. The origination of an external leak can be narrowed down considerably during cleaning.
Caution: To avoid danger of being burned, do not remove radiator or reservoir cap while engine and radiator are still hot, as fluid and steam can be blown out under pressure.
Before using a radiator pressure tester, wet relief valve and pressure valve with engine coolant or water.
When performing pressure tests, keep tester at an angle of over 30° above horizontal.
Refer to published specifications to determine proper cooling system operating pressures.
1. Remove radiator or reservoir cap.
2. Fill radiator and overflow to proper level with coolant.
3. Inspect overflow tube and overflow bottle for dents, kinks, or internal obstructions.
4. Wipe out inside of filler neck. Inspect lower inside sealing seat of filler neck for nicks, dirt and solder bumps.
5. Inspect cams on outside of filler neck. If cams are bent down or up, seating of pressure cap valve and tester seal will be affected. If cams are damaged, have filler neck replaced by a reputable radiator repair service facility.
6. Attach a radiator pressure tester and rotate tester head until locking ears contact stops on radiator.
7. Operate pump until indicator on gauge reaches just beyond color band for recommended pressure for vehicle, Fig. 1.
8. If pressure drops, inspect hoses, radiator or water pump for leaks. If no external leaks are found and pressure drops, inspect heater core, cylinder block and head.
9. Once leak has been detected repair system as required.

Fig. 1 Cooling system pressure chart

    Coolant Drain, Flush & Refill
    Warning: To avoid being burned, do not remove the radiator cap or surge tank cap while the engine is hot. The cooling system will release scalding fluid and steam under pressure if ...

    Cooling System Leak, Inspection
    A visual inspection must always be performed to confirm the presence of aftermarket components, potential collision damage, or areas of concern. Always clean all external c ...

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