Excessive Antifreeze Concentrations Can Cause Overheating

All Caterpillar Engines

Most formulated antifreezes contain chemical compounds which rely on water to keep the compounds dissolved. If little or no water is used with antifreeze, the compounds will come out of the solution and build up on hot surfaces. Not only do the deposits result in overheating, but more seriously, they can lead to water pump seal leakage and/or cylinder head cracking.

These compounds will appear as hard, greyish to white deposits, and they may be very smooth or porous. They will normally form on prechambers and the water passages in the cylinder head. See Illustration 1.

Illustration 1. Deposits on prechamber.

These compounds will usually redissolve in water. Follow the “Procedure to Dissolve Deposits”.

Procedure To Dissolve Deposits
1. In order to dissolve these deposits, drain the coolant and fill the cooling system with clear water.

2. Fasten cardboard or light plywood to the radiator on the opposite side of the fan.

3. Start and run the engine at high idle rpm with no load. Allow the temperature of the coolant to increase, but do not exceed 93°C (200°F). The radiator cap is to be set loosely on the filler neck during this operation and load is not to be applied to the engine.

4. After a one hour period, decrease engine speed to low idle. Remove the material blocking the radiator and continue to run the engine at low idle for five minutes.

Illustration 2 shows the same prechamber after 30 minutes. Illustration 3 shows the same prechamber after 60 minutes.

Illustration 2. Prechamber after 30 minutes.

5. Stop the engine, drain and discard this water.

6. Replace the water conditioner filter and element if used. If a water conditioner filter and element are not used, add cooling system conditioner to obtain a 3 to 6% concentration after filling the system.

7. Refill the cooling system to the full mark with a 50/50 mixture of clean antifreeze and water for coolant. Note: If bulk antifreeze or mix is used, obtain a sample in a clear sample bottle and let it stand for 30 minutes. If the antifreeze mix is discolored, has particles floating in it or has a layer of darkish material floating on the surface, the mix should be filtered through a filter media before pouring the mix into the cooling system. Start the engine and top off to the full mark once again.

Illustration 3. Prechamber after 60 minutes.

Coolant mixtures in excess of 50% antifreeze should not be used unless temperatures below -34°C (-30°F) are expected. Increase to 60% antifreeze in this case but as the outside air temperatures start to be consistently above 0°C (32°F), switch back to the 50/50 mixture.

Antifreee concentrations in excess of 63% provide less rather than more freeze protection.

A good practice to follow after operating an engine is to return the engine speed to low idle for 5 minutes before shutting the engine down. This reduces the surface temperature of the prechambers, heads and liners minimizing localized boiling at these areas. This will also reduce the plating effect of the compounds in the coolant.

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