REVISED:DIESEL HEAD GSKT.FAIL NO COOLANT BYPASS SYSTEM

1982 V-6 LT7 DIESEL ENGINE

"Please discard previous bulletin 82-T-103, Section 6B due to error in part number."

1982 model V-6 diesel 6000's were built with a slightly different cooling system than 1983 and 1984 models. The later models have coolant bypass system. This system chances coolant flow through engine during closed thermostat operation and reduces thermostat cycling. Under some driving and temperature conditions, this contribute to a head gasket failure. Therefore, if a head gas failure is encountered, replace both head gaskets and install coolant bypass system as outlined. Use the head gaskets listed in kits below.

Diesel cylinder heads often exhibit hairline cracks between the in and exhaust valve seats. This is not considered unusual and 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 bubbles coming out of the coolant overflow hose.

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

SERVICE PROCEDURE

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

2. Remove the Fan Control Sensor from the intake manifold. Apply a sealer such as part no. 1050026 or equivalent to the threads fitting, part no. 22519880 and install in the intake manifold shown in Item 1 in Figure 1. Apply sealer to the Fan Con 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 (Figure 1) Without Air Conditioning (Figure 2) -------------------------------- ----------------------------------- Hose Asm. 22521633 Hose Asm. 22521633 Hose Clamps (2) 14052374 Hose Clamps (2) 14052374 Straps (2) 11504726 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.