95.014: Bus Cooling Systems


The manufacturing of antifreeze requires extensive experience and technology to prepare a product that will meet standard performance requirements and retain its inhibitors in solution. An antifreeze or coolant is said to be stable if little or no solid precipitates (falls out) during use. It is said to be unstable if solids, typically phosphate and/or silicate are observed in significant amounts in solid form. These deposits are problematic and will contribute to overheating by adhering to and insulating the heat exchange surfaces and/or interfering with the fluid flow in the cooling system. These precipitates may also shorten water pump life.

Service Recommendation:

A system that has overheated due to inhibitor dropout must be serviced immediately to prevent engine damage. The system is extremely contaminated.

The service involves:

  1. Drain the unstable coolant from the vehicle.
  2. Clean the system to remove precipitates.
  3. Refill the system with low TDS, phosphate free antifreeze/coolant

Use Penray 2001 On Line Cooling System Cleaner to clean the system. Follow manufacturers’ use Instructions, to minimize the chance of recurrence, refill the system with a phosphate free, low silicate fully formulated antifreeze mixed with 50% distilled, deionized or reverse osmosis cleaned water. Maintain the system according to the engine manufacturer’s recommendations. Avoid overuse of supplemental coolant additives.