ENGINE/TRANSMISSION COOLING SYS. MODIFIED ADD. COOLING

SUBJECT: ENGINE/TRANSMISSION COOLING

MODELS: 1979-1981 M.D. CONVENTIONALS WITH 427-V8 AND MT640/650 AUTOMATIC TRANSMISSION

Effective with interim 1981 Production (May 13, 1981) the cooling system of the above subject vehicles was modified to provide additional engine/transmission cooling capacity for extreme modes of operation (ie. stationary pumping operations, prolonged converter operation, etc.)

The system modifications include a greater frontal area radiator with a high capacity transmission oil cooler and a viscous fan drive assembly with an increased air flow fan.

PARTS INFORMATION

The following parts can be ordered through WDDGM for field installation.

Part Number Quantity Description ----------- -------- --------------------------- 3050192 1 Radiator (744 sq. in., with 18" Ten-Plate Cooler) 3901449 4* Rubber Insulator Cushions 2038374 1 Shroud 3035086 1 Surge Tank Assembly 695551 2 Surge Tank Brackets NPN 2 Anti-Squeak (Procure Locally) 850994 1 Cap Surge Tank Plumbing - Pressure cap side 9438373 1 Hose 128281 3 Clip 11500918 2 Bolt 11500323 2 Washer 11500760 2 Nut 11501906 1 Band 3720469 1 Hose 1470029 2 Clamp 409797 1 Strap 3883018 1 Nipple 444056 1 Elbow 444034 1 Reducer

*Only if required - See Step 3

Part Number Quantity Description -------------------- --------- ---------------------- Surge Tank Plumbing - RH Side 2378715 1 Hose

477402 2 Clamp

2415944 1 Elbow

444000 1 Adapter

703042 1 Hose

1470030 2 Clamp 2028748 1 Viscous Fan Drive Assembly 2032706 4 Studs - Fan Drive to Water Pump 225854 4 Nuts - Fan Drive to Water Pump 2041379 1 Fan Blade Assembly (7-Blade) 103320 6 Washers - Fan-to-Drive 9439493 6 Nuts - Fan-to-Drive

Additional Parts

With T50 - Fiberglas Hood:

Part Number Quantity Description ------------ --------- -------------------------------- 2039386 1 Radiator Cover Support Assembly 2039383 2 Radiator Strut Rods 11504595 2 Bolt - Surge Tank Bracket Mounting 120382 2 Washer - Surge Tank Bracket Mounting Without T50 2039665 2 Radiator Support Assembly 2039667 2 Radiator Support Bracket Assembly 2038371 2 Surge Tank Support Assembly 11504596 2 Bolt - Surge Tank Bracket Mounting 120382 2 Washer - Surge Tank Bracket Mounting 11500424 2 Nut - Surge Tank Bracket Mounting

Service Procedure

1. Remove the following cooling system components:

Fan Blade Assembly Fan Drive Assembly Fan Shroud Coolant Recovery Bottle Radiator

2. Install new radiator using brackets 2039665 and 2039667 (with "T50" fiberglass hood use 2039386 radiator cover support assembly and 2039383 strut rods).

3. Inspect rubber insulator cushions and replace as necessary.

4. Install shroud.

5. Install surge tank using 2038371 support assembly and 695551 brackets, two pieces of "anti-squeak", 11504596 bolts, 120382 washers and 11500424 nuts. (With "T50" fiberglass hood use 695551 brackets and "anti-squeak" and mount directly to the radiator cover assembly using 11504595 bolts and 120382 washers.)

6. Make plumbing connections to surge tank. (Refer to Figure No. 1).

7. Install fan and fan drive assembly using installation instructions found in Service Manual X-8033, Page 6B-19.

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.