GM Service Manual Online
For 1990-2009 cars only

Leak Testing Procedure (On Vehicle)

Tools Required

J 24460-01 Cooling System and Cap Pressure Tester

Caution: Under pressure, the temperature of the solution in the radiator can be considerably higher, without boiling. Removing the radiator cap while the engine is hot (pressure is high), will cause the solution to boil instantaneously, with explosive force. The solution will spew out over the engine, fenders, and the person removing the cap. Serious bodily injury may result. Flammable antifreeze, such as alcohol, is not recommended for use at any time. Flammable antifreeze could cause a serious fire.

Caution: In order to help avoid being burned, do not remove the radiator cap while the engine and the radiator are hot. Scalding fluid and steam can be blown out under pressure if the cap is removed too soon.

  1. After the system has cooled, remove the radiator/surge tank pressure cap.

  2. Object Number: 11658  Size: SH
  3. Connect the cooling system tester J 24460-01 to the radiator/surge tank.
  4. Apply normal system operating pressure. Do not exceed 138 kPa (20 psi).

  5. Object Number: 1374  Size: SH
  6. Watch the gauge needle for an indication of a leak. Examine all cooling system connections and components, including the radiator and the heater core, for leaking coolant.
  7. Tighten the hose connections or repair as required.

  8. Object Number: 1375  Size: SH
  9. Check the radiator/surge tank cap with J 24460-01 in order to ensure the cap maintains the correct pressure.
  10. If the radiator leaks during the pressure test, mark the leak area so the leak can be located once the radiator has been removed from the vehicle.

Transmission Oil Cooler Leaks

A leak in the transmission oil cooler may produce a variety of problems. Any of the following signs may indicate a leak in the transmission oil cooler:

    • The frequent addition of transmission fluid when no obvious external leaks are noticed.
    • Discoloring of engine coolant.
    • Accumulation of a milky substance in the radiator. This substance may be similar to that produced by engine oil in the coolant.

Any of these symptoms require further investigation.