For 1990-2009 cars

# ENGINE COOLING SYSTEM LEAKS (DIAGNOSIS INFORMATION)

ENGINE COOLING SYSTEM LEAKS (DIAGNOSTIC PROCEDURE) THIS BULLETIN CANCELS AND REPLACES BULLETIN 88-6-115

#### VEHICLES AFFECTED 1980-89 GM MODELS WITH CPC ENGINES ----------------- The following Engine VIN Codes are also involved:

Passenger Cars: T - U - W - Y - Z - 1 - 2 -3 - 4 - 5 - 6 - 7 - 8 - 9

Trucks : J - N - Z

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. Assure the cooling 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. THE WATER PUMP SHOULD BE REPLACED ONLY IF COOLANT IS DRIPPING FROM THE WEEP HOLE WHILE THE ENGINE IS IN OPERATION OR WHILE THE COOLING SYSTEM IS PRESSURIZED.

Minor engine coolant system leaks not corrected through normal service procedures, may be corrected by adding (2) sealant pellets, P/N 3634621, to the coolant system. The pellets are available from CANSPO.

The pellets should be added to the coolant system under the following conditions:

1). Vehicles with minor coolant leaks/loss that can not be corrected through normal service procedures.

and/or

2). Engine repair work that requires coolant drainage and replacement with new coolant.

The two sealant pellets should be installed into the radiator filler neck. The pellets may have to be crushed prior to installation.

#### NOTICE: DO NOT ADD THE SEALANT INTO THE COOLANT RECOVERY BOTTLE. THE USE OF THE SEALANT PELLETS MAY CAUSE A FILM TO APPEAR AROUND THE SIDES OF THE COOLANT RECOVERY BOTTLE. THE PRESENCE OF THIS FILM IS CONSIDERED TO BE NORMAL.

Following installation of the pellets, run the engine for approximately 15 minutes, then check for coolant leakage.

Use applicable labor time and operation codes.

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.