- Engine:
- C7 (S/N: C7S1-UP)
- C9 (S/N: C9S1-UP)
- C13 (S/N: S3C1-UP; LEE1-UP)
- C15 (S/N: SDP1-UP; B5R1-UP)
- C9 (S/N: C9S1-UP)
Introduction
The article below explains the proper interpretation of oil samples that are taken from 2007 On-Highway Engines. The oil samples that are taken in the early mileage of these engines have shown some unique characteristics. These characteristics could be misunderstood. A misinterpretation of the results from the oil sample could lead to unnecessary inspections or repairs. The problem that is identified below does not have a known permanent solution. Until a permanent solution is known, use the solution that is identified below.
Problem
Initial oil samples from 2007 On-Highway Engines have shown highly elevated values of potassium and aluminum. The elevated values may occur during the first two to three oil changes. After the first two to three oil changes, the potassium will decrease to less than 25 parts per million. Also, the aluminum levels will decrease to 130 parts per million or less depending on the oil change interval.
The source of these elements has been traced to the brazing flux that is used in order to manufacture the aluminum Air-to-Air Aftercooler (ATAAC). The brazing flux is made from a compound that contains a high concentration of potassium and aluminum. Residual amounts of this flux remain in the new ATAAC. The air from the turbocharger and the air from the circuit of the Clean Gas Induction (CGI) flow through the ATAAC during operating conditions. The moist air from the CGI reacts chemically with the brazing flux. This reaction releases small amounts of potassium and aluminum into the air stream for combustion. These elements enter the engine oil through the oil film on the cylinder liners.
Potassium is commonly used as an indicator of coolant contamination in an oil sample. Aluminum is commonly used to indicate severe bearing wear or stress on aluminum engine components. The correct interpretation of the oil sample is very difficult when elevated values of potassium and aluminum are present.
Solution
Potassium and aluminum from the core of the ATAAC not cause abnormal wear of the engine. Iron, lead, and chromium values are not affected by this source of potassium and aluminum. The service life of the core of the ATAAC is not reduced by the reaction with the brazing flux.
Potassium could reach 700 parts per million and aluminum could reach 500 parts per million during the first two to three oil changes according to current data. The ratio of potassium to aluminum varies widely on these initial oil samples. In many engines, the potassium value is higher than the aluminum value. After the first two to three oil changes, the potassium will decrease to less than 25 parts per million. Also, the aluminum levels will decrease to 130 parts per million or less depending on the oil change interval.
Elevated potassium from the ATAAC brazing flux will make the identification of coolant contamination more difficult. Most heavy-duty coolants contain high concentrations of sodium and/or potassium compounds. The sodium and/or potassium compounds are used in order to determine if coolant has entered the engine oil. An indicator of coolant contamination in the oil sample is 25 parts per million or more of sodium and/or potassium. The ATAAC brazing flux may temporarily elevate potassium levels to several hundred parts per million. If there are elevated levels of potassium, the analyst must use other indicators in order determine if the engine oil has been contaminated with coolant. The following items are other indicators of coolant contamination.
- 25 parts per million or more of sodium
- positive water
- elevated levels of boron, magnesium, silicon, and copper
A trained S·O·S analyst uses these other indicators in order to determine if the oil is contaminated with coolant. Elevated aluminum values usually indicate severe wear on connecting rod or main bearings. The S·O·S analyst should look for correlating evidence of bearing wear and elevated aluminum levels when compared to a sample that is taken at an earlier mileage. The S·O·S analyst should look for other evidence of bearing wear. If bearing wear is occurring, there will also be highly elevated lead values and elevated iron values. The lead is part of the overlay on the bearing surface. If lead values are normal, the bearing wear is highly unlikely. Severe bearing wear will also increase the wear on iron components within the engine. The source of the iron wear is from the crankshaft.
After these initial spikes in potassium and aluminum, the results from the oil samples should return to normal. Continue to use trend analysis and S·O·S guidelines for evaluating subsequent oil samples.