For 1990-2009 cars

# ENGINE COOLING SYSTEM LEAKS (DIAGNOSIS INFORMATION)

ENGINE COOLING SYSTEM LEAKS

ALL MODELS

The cause of engine cooling system leaks which may occur may be due to several possible reasons. Refer to the Service Manual to properly diagnose the reason for a leak. MAKE SURE THE SYSTEM IS FULL OF COOLANT BEFORE PERFORMING THE DIAGNOSIS. Also, the following systems should be inspected for proper function:

1. All hose joints for possibility of loose or misaligned clamps.

2. All gasketed joints for possibility of loose fasteners, damaged gaskets, or damaged surfaces.

3. Coolant recovery system for possibility of vacuum leaks or a damaged seal surface at the coolant filler cap assembly.

4. Water pump assembly for possibility of a slight leak from the weep hole.

#### NOTICE: A VERY SLIGHT AMOUNT OF WEEPAGE OCCURS AT THE WATER PUMP WEEP HOLE DURING NORMAL OPERATION. TRACKS OF RESIDUE FROM THE LOWER WEEP HOLE ARE NOT UNUSUAL. ONLY REPLACE THE WATER PUMP IF COOLANT IS DRIPPING FROM THE WEEP HOLE WHILE THE ENGINE IS IN OPERATION OR WHILE THE COOLING SYSTEM IS PRESSURIZED.

The use of an engine coolant supplement or sealant pellets, P/N 3634621, is recommended to eliminate slight leaks from the cooling system. Two sealant pellets should be added to the cooling system through the radiator filler neck.

#### NOTICE: DO NOT ADD THE SEALANT INTO THE COOLANT RECOVERY BOTTLE.

After adding the sealant to the cooling system, the engine should be allowed to run for approximately 15 minutes to dissolve the sealant and verify that the leak has been eliminated.

DO NOT REPLACE THE WATER PUMP ASSEMBLY IF A LEAK IS NOT EVIDENT.

#### NOTICE: THE USE OF AN ENGINE COOLANT SUPPLEMENT MAY CAUSE A FILM TO APPEAR AROUND THE SIDES OF THE COOLANT RESERVOIR BOTTLE. THE PRESENCE OF THIS FILM IS CONSIDERED TO BE NORMAL.

Use applicable labor operation and times.

General Motors bulletins are intended for use by professional technicians, not a "do-it-yourselfer". They are written to inform those technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions and know-how to do a job properly and safely. If a condition is described, do not assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See a General Motors dealer servicing your brand of General Motors vehicle for information on whether your vehicle may benefit from the information.