DIESEL HEAD GASKET FAILURE NO COOLANT BYPASS SYSTEM

VEHICLES AFFECTED: 1982 'A' Series Vehicles Equipped with V-6 (LT7) Diesel Engine

1982 'A' Series equipped with V-6 Diesel Engine (LT7) were built with a slightly different cooling system than 1983 and 1984 models. The later models have a coolant bypass system. This system changes coolant flow through the engine during closed thermostat operation and reduces thermostat cycling. Under some driving and temperature conditions, this may contribute to a head gasket failure. Therefore, if a head gasket failure is encountered, replace both head gaskets and install the coolant bypass system as outlined. Use the head gaskets listed in the kits below.

Diesel cylinder heads often exhibit hairline cracks between the intake and exhaust valve seats. This is not considered unusual and this condition does not require replacement of the cylinder heads.

DIAGNOSIS

Failure of a head gasket may result in either or both of these conditions:

1. Compression gases leaking into the coolant which is evident by bubbles coming out of the coolant overflow hose.

2. Compression leak between the head and block at the end of the head. This makes a popping or hissing sound.

SERVICE PRODCEURE

1. Replace the head gaskets as outlined in the service manual. Use Overhaul Gasket Kit No. 22527056 or Cylinder Head Gasket Kit No. 22527055.

2. Remove the Fan Control Sensor from the intake manifold. Apply a sealer such as part no. 5725836 or equivalent to the threads of fitting, part no. 22519880 and install in the intake manifold as shown as Item 1 in Figure 1. Apply sealer to the Fan Cuntrol Sensor threads and install in the fitting.

3. Remove the water outlet. Remove the thermostat and install a 82 DEG C (180 DEG F) thermostat, part no. 3054228.

4. Remove the heater to pump pipe and install pipe no. 22520032, shown as Item 2 in Figure 1.

5. Install fitting-to-pipe hose shown as Item 3 in Figure 1 or 2 as applicable. Install the straps or clamps as shown.

With Air Conditioning Without Air Conditioning (Figure 1 ) (Figure 2)

Hose Asm. 22521633 Hose Asm. 22521633 Hose Clamps (2) 14052374 Hose Clamps (2) 14052374 Straps (2) 14009215 Clamp 3017087

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.