Attention: TDR Forum Junkies 
I recently discovered a critical engine problem with one of my non cummins powered busses. The cylinder liners are pitted to the point that coolant will leak into the combustion chamber and vise versa.
The problem is referred to cavitation aka liner pitting. This is due to the relatively thin cylinder wall of an engine liner or "sleeve" expanding and contracting very rapidly under the stresses of the combustion cycle as the piston is forced down on combustion stroke. The rapid movement of the liner causes very small air pockets in the coolant along the O. D. of the liner wall to form and burst thus "working" to "eat" away at the liner wall.
Engine containing wet liners are known as heavy duty engines and can be easily rebuilt while still in the truck frame. Pull the liner and replace with new, thus creating a new cylinder wall. The problem with said design is liner pitting. Our CTD engines are of a design known as Parent Block aka cast in block design. No movement of cylinder walls... no pitting.
This condition can be reasonably eliminated with the use of proper chemicals added to the coolant known as SCA, by way of a chemically charged filter and or liquids additive. This must be done from the start, don;t wait to reach 100,000K. Many engine manufacturers recommend the use of a filter and liquid chemicals for many reasons other than preventing liner pitting. Many of my school busses have a coolant filter, wet sleeve or not. Keeps the system clean and slowly adds conditioner to coolant. Engine coolant would not require replacement if it did not become contaminated with oil, rust, etc. Nor would it require replacement if it's conditioning chemicals are replenished as they are depleted.
There are two common types of heavy duty antifreeze, Propylene and ethylene-glycol base. Ethylene is the common green stuff we are all familiar with. Propylene is commonly blue and can be mixed with ethylene-glycol. However, the two are very much different. Do not use the hydrometer(floating ball) method to test propylene base coolant. A tool known as the refractometer is used and can be used to test both types. A mixture of 50/50 will not read the same for each. The fleetguard coolant part No. CC2830 is propylene base which is considered a lifetime coolant providing you change the filter, test for proper strength of it's conditioning chemicals (adding when required) and use clean/soft water for the initial fill. Antifreeze is essential. Never use straight water. Antifreeze lowers the coolant freezing point and raises it's boiling point. Corrosion inhibitors protect the system components.
If I have left anything out or made an error please feel free to comment. Should anyone have additional information that may be of help to any and all truck owners, please post.
The problem is referred to cavitation aka liner pitting. This is due to the relatively thin cylinder wall of an engine liner or "sleeve" expanding and contracting very rapidly under the stresses of the combustion cycle as the piston is forced down on combustion stroke. The rapid movement of the liner causes very small air pockets in the coolant along the O. D. of the liner wall to form and burst thus "working" to "eat" away at the liner wall.
Engine containing wet liners are known as heavy duty engines and can be easily rebuilt while still in the truck frame. Pull the liner and replace with new, thus creating a new cylinder wall. The problem with said design is liner pitting. Our CTD engines are of a design known as Parent Block aka cast in block design. No movement of cylinder walls... no pitting.
This condition can be reasonably eliminated with the use of proper chemicals added to the coolant known as SCA, by way of a chemically charged filter and or liquids additive. This must be done from the start, don;t wait to reach 100,000K. Many engine manufacturers recommend the use of a filter and liquid chemicals for many reasons other than preventing liner pitting. Many of my school busses have a coolant filter, wet sleeve or not. Keeps the system clean and slowly adds conditioner to coolant. Engine coolant would not require replacement if it did not become contaminated with oil, rust, etc. Nor would it require replacement if it's conditioning chemicals are replenished as they are depleted.
There are two common types of heavy duty antifreeze, Propylene and ethylene-glycol base. Ethylene is the common green stuff we are all familiar with. Propylene is commonly blue and can be mixed with ethylene-glycol. However, the two are very much different. Do not use the hydrometer(floating ball) method to test propylene base coolant. A tool known as the refractometer is used and can be used to test both types. A mixture of 50/50 will not read the same for each. The fleetguard coolant part No. CC2830 is propylene base which is considered a lifetime coolant providing you change the filter, test for proper strength of it's conditioning chemicals (adding when required) and use clean/soft water for the initial fill. Antifreeze is essential. Never use straight water. Antifreeze lowers the coolant freezing point and raises it's boiling point. Corrosion inhibitors protect the system components.
If I have left anything out or made an error please feel free to comment. Should anyone have additional information that may be of help to any and all truck owners, please post.
Looked at a new bus awhile ago and can only say there is no reason that the same set-up can't be incorporated into the cooling system on our CTD. 
Maybe start a new trend! At any-rate, hope this helps. 
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