TM 5-3895-346-14
ENGINE OVERHAUL
COOLING SYSTEM
be flushed thoroughly to remove the contaminants before the engine is seriously damaged. One possible
cause of such contamination, that is damaging to the engine if it is not corrected immediately, is a cracked oil
cooler core. With a cracked oil cooler core, oil will be forced into the cooling system while the engine is
operating, and when it is stopped, coolant will leak into the lubricating system.
Coolant contamination of the lubricating system is especially harmful to engines during the cold season when
the cooling system is normally filled with an ethylene glycol antifreeze solution. If mixed with the oil in the
crankcase, this antifreeze forms a varnish which quickly immobilizes moving engine parts.
To remove such contaminants from the engine, both the cooling system and the lubrication system must be
thoroughly flushed as follows:
COOLING SYSTEM
If the engine has had a failure resulting in the contamination of the cooling system with lubricating oil, the
following procedure is recommended.
1. Prepare a mixture of Calgon, or equivalent, and water at the rate of two ounces (dry measure) to one
gallon of water.
2. Remove the engine thermostats to permit the Calgon and water mixture to circulate through the
engine and the radiator or heat exchanger.
3. Fill the cooling system with the Calgon solution.
4. Run the engine for five minutes.
5. Drain the cooling system.
6. Repeat Steps 3 through 5.
7. Fill the cooling system with clean water.
8. Let the engine run five minutes.
9. Drain the cooling system completely.
10. Install the engine thermostat.
11. Close all of the drains and refill the engine with fresh coolant.
LUBRICATION SYSTEM
When the engine lubricating system has been contaminated by an ethylene glycol antifreeze solution or other
soluble material, the following cleaning procedure, using Butyl Cellosolve, or equivalent, is recommended.
WARNING
Use extreme care in the handling of these chemicals to
prevent serious injury to the person or damage to
finished surfaces. Wash off spilled fluid immediately
with clean water.
If the engine is still in running condition, proceed as follows:
1. Drain all of the lubricating oil.
2. Remove and discard the oil filter element. Clean and dry the filter shell and replace the element.
3. Mix two parts of Butyl Cellosolve, or equivalent, with one part SAE 1O engine oil. Fill the engine
crankcase to the proper operating level with the mixture.
4. Start and run the engine at a fast idle (1,000 to 1,200 rpm) for 30 minutes to one hour. Check the oil
pressure frequently.
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