Re: 1991 DTA360 Coolant System Flush Procedure
From the owners manual of my BB:
HEATER BLEEDING INSTRUCTIONS
Use of antifreeze (ethylene glycol type only) is recommended for summer or winter operation because of its corrosion inhibition and lubrication properties. A 50-50 solution of antifreeze and water is preferred and it gives freeze protection to about 30 degrees F below zero. Ultimate protection is attained at 68% antifreeze (about 92 degrees F below zero); a higher concentration of antifreeze should never be used. Check engine operations and maintenance manuals on recommendations on use of coolant additives.
If it becomes necessary to completely refill the chassis coolant system, the following procedure must be followed to insure adequate heater bleeding. During the bleeding process, it will be necessary to remove the radiator cap and refill cooling system several times to insure adequate coolant is available to replace purged air and coolant lost when bleeding.
WARNING: Extreme care must be used when removing radiator cap. As coolant becomes hot, pressure is built up in the cooling system. Rapid venting and/or removal of radiator cap will cause coolant to boil up and spray out and can result in serious burns. Slowly vent off pressure before removing radiator cap.
1. With the engine off, shut all engine heater gate valves or clamp closed all heater hoses as close to engine as possible.
2. Fill cooling system completely, including surge tank with coolant and run engine for a few minutes to bleed air from cylinder block and heads.
3. Open the heater hose supply line gate valve or unclamp supply line hose. Refer to following pages, (Heater Cutoff Valves) for heater cutoff valve location. Turn on heater water pump.
4. Using a suitable container to catch coolant, run engine between 2,000 and 3,000 RPM, loosen bleeder valve located in heater hose return line. Bleed air and coolant through bleeder valve until air is elimi- nated from heater system. (Stop bleeding when continuous stream of coolant comes from bleeder valve.) Note: It will be necessary every few moments to refill the radiator or surge tank.
5. When all of the air has been purged from the heater system, open gate valve in heater hose return line or unclamp return hose.
6. Run engine between 2,000 and 3,000 RPM until thermostats open. To assist in deaerating the entire cooling system, accelerate the engine a few times before and after thermostats open.
Note: Thermostats have opened when upper radiator tank and radiator hose becomes hot.
7. Refill cooling system including radiator and surge tank.
WARNING: Never idle engine in closed areas. Never sit in a parked or stopped vehicle for any extended amount of time with the engine running; exhaust gases, particularly carbon monoxide, may build up. These gases are harmful and potentially lethal.
Carbon monoxide is colorless and odorless, but can be present with all other exhaust fumes. Therefore, if you ever smell exhaust fumes of any kind inside your vehicle, have it inspected immediately by your dealer and have the condition corrected. Do not drive with exhaust fumes present.