Engine Oil Contains Elevated Lead (Pb) {1348} Caterpillar

Caterpillar Products Machine Engines

All 3500 Series

Introduction

This Special Instruction provides guidance for when levels of lead (Pb) in engine oil samples are elevated to a point of Action Required according to S·O·S wear tables.

Lead in engine oil does not always come from main or rod bearings. However this Special Instruction presumes that the bearings are the most likely source. Lead from other sources, such as excessive thrust washer or bronze bushing wear, most commonly is accompanied by highly elevated levels of copper (Cu).

Note: This publication is to be used to explore the root cause of elevated lead in oil samples. Due to the risk of debris introduction from physical bearing inspections or replacements, investigate the root cause thoroughly prior to disassembling the engine.

Additional Resources

Professional classroom instruction on oil sampling, analysis, and interpretation is available, course 08E1017 S·O·S Services Interpretation Training I. Course information, help sheets, wear tables, and community discussion is available under S·O·S Services on the Knowledge Network (https://kn.cat.com). Other helpful resources:

• Operation and Maintenance Manual, SEBU6250, "Caterpillar Machine Fluids Recommendations"

• Special Instruction, SEBD0640, "Oil and Your Engine"

Action Required : Example

Illustration 1	g03403230
Typical example wear table. Values subject to change.

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Example of a trend chart with lead level elevated to Action Required

If an oil analysis returns from the lab with an elevated level of lead and action is required, follow the steps listed below.

1. Review and Validate the Sample

2. Determine the Root Cause - Wear or Chemistry

3. Resolve and Proceed

Review and Validate the Sample

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Sample Collection, Age, and Analysis

Verify that the sample was collected and delivered correctly. Verify that the lab has been used in the past. Verify the hours of the oil. Was an oil change missed?

Compare to Trend

Has the lead level in the oil from this engine been steady or trending upward in recent samples? If the lead level is trending up, has the rate of increase been gradual or rapid? Has a follow-up sample been taken and analyzed to confirm a rapidly increasing trend? If the trend is indeed increasing rapidly, the engine should be shut down and action taken immediately to investigate and resolve the problem.

Service Records

Carefully consider service records including recent component changes, modifications to lubrication, cooling or fuel systems, or any adjustments to the oil renewal system if equipped. Do service records reflect any change of suppliers or formulations of oil, coolant, or fuel? Lead is common in various greases sometimes used as assembly aids.

Operation Records

Consider operational changes including major changes in haul cycle, profile, shift, operator, and so on. Is the operator noting anything unusual? Has the fuel burn rate changed or have there been any changes to the rate of oil consumption or frequency/volume of oil additions?

Consider Collecting Another Sample

Has resampling been considered after changing oil and filters? Has this sample been collected early due to elevated lead in the previous sample?

Determine Root Cause

Lead is most often removed from bearings by mechanical wear or chemical wear.

Mechanical Wear

Mechanical wear of main and connecting rod bearings most commonly originates from one or more of the sources listed below:

• Dirt/Debris Introduction from Service or Operation

• Dirt Ingestion Through the Air System

• Abnormal Operating Conditions

• Out of Specification or Damaged Components

Dirt/Debris Introduction from Service or Operation

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Dirt and debris can be introduced into the lubrication system anytime the engine is opened for service, repair, or oil additions. Review service and operation records to understand when the engine has been opened and to identify other possible sources for dirt or debris entry, including changes in personnel. Routine inspection of oil filter media and magnetic drain plugs for signs of debris is encouraged.

Note: The first few samples from new or newly rebuilt engines often contain elevated levels of silicon from seal materials. Elevated levels of silicon in new or newly rebuilt engines can be normal.

Dirt Ingestion Through the Air System

The chemical makeup of dirt is regionally unique, but generally dirt contains at least silicon and aluminum in a ratio close to Si:Al = 3:1. Dirt ingestion through the air system often generates elevated levels of iron and chromium first from liners, pistons and rings via abrasive wear. Levels of lead often rise shortly thereafter as dirt enters the lubrication system. Regular testing to find and fix leaks in the air system is encouraged. Refer to the following for additional information for testing the air system:

• Testing and Adjusting, RENR8327, "Air Inlet System - Test and Inspect"

• Testing and Adjusting, SENR1450, "Air Inlet System - Test and Inspect"

• Service Magazine, SEPD0712, "Procedure to Test the Air Induction System"

Abnormal Operating Conditions

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Review records for evidence of overspeed, low oil level, low oil pressure, high coolant temperatures, and other abnormal operating conditions. If the product is equipped with an overspeed protection system, the operator should enable the system and leave the system engaged. Disabling or overriding overspeed protection systems can rapidly accelerate bearing wear and increase risk of component breakage. Pumping small quantities of oil and usage of oil with incorrect chemistry can aerate the oil and accelerate bearing wear. High coolant temperatures can also increase bearing wear and lead loss by reducing oil viscosity and accelerating oxidation. Lead levels can rise rapidly when operating in abnormal conditions. Extra diligence with a quality oil sampling and analysis program is encouraged.

Out of Specification or Damaged Components

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When lead levels are elevated alone, without contaminants such as water, glycol, or fuel, deterioration indicators (oxidation, nitration, sulfation), or other wear elements (Fe, Cr, Ni, Cu, Sn, Si, Al), crankshaft and connecting rod history becomes a common area of focus. How many hours are on the crankshaft and connecting rods? Has the crankshaft been polished, or ground and polished? Did the salvage procedure follow best practices as published in Reuse and Salvage Guidelines, SEBF8041, "Specifications for Crankshafts in 3500 Engines" and Reuse and Salvage Guidelines, SEBF8042, "Procedure for Grinding and Polishing the Crankshaft" Were correctly sized bearings installed if the crankshaft has been ground? Over-polishing of crankshaft journals often creates journal inconsistencies which can accelerate bearing wear and lead loss.

End of Life Components

Wear metal concentrations tend to rise as components reach the end of the components service life. If the engine components are approaching targeted replacement points, a gradual increase in wear metal concentration can be normal. Pay close attention to oil analysis results. Slight reductions in oil change interval, changes to the usage profile, or similar adjustments may be required to reach the targeted replacement points.

Chemical Wear

Problems with oil chemistry that contribute to loss of lead from bearings most commonly originate from one or more of the sources listed below:

• Extended Usage of Old Oil

• Fuel Contamination (Dilution)

• Coolant Contamination

• Oil Deterioration and Soot Contamination

Extended Usage of Old Oil

Illustration 7	g03403243

There is no other maintenance procedure as important as regularly changing oil and filters.

Operation and Maintenance Manuals specify a maximum oil change interval (OCI) based on close monitoring of wear metals/oil condition and the following targeted milestones: service hours or calendar time, whichever comes first. Products that operate in severe conditions, or that have high fuel burn rates, may require more frequent oil changes. Refer to Special Instruction, SEBD0640, "Oil and Your Engine" for additional information.

Fuel Contamination (Dilution)

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Raw fuel can enter the lubrication system directly from leaking injector seals, transfer pump seals, and cracked fuel supply manifolds. Unburned fuel can also enter the lubrication system indirectly through leaking injector seals, injectors with poor spray patterns, by frequent cold starting and by misguided efforts to alter fuel or timing profiles. Unburned fuel in the combustion chamber can wash the oil film from the liners, pistons and rings resulting in increasing levels of iron and chromium in engine oil samples.

As oil becomes contaminated (diluted) with fuel, the oil viscosity drop, which reduces the thickness of the oil film that separates the crank journals from the bearings. The loss of viscosity can rapidly accelerate bearing wear.

Dropping viscosity is a far better indicator of fuel dilution than wear metal levels. A viscosity decrease of 2 cSt or more is usually a sign of fuel dilution. Careful attention to viscosity trends is encouraged.

The levels of lead and other wear metals in oil samples may not increase significantly as a result of fuel dilution, however bearing damage from fuel dilution can be veryswift.

Fuel in engine oil also dilutes important oil additives, reducing effectiveness. Refer to Troubleshooting, RENR5622, "Fuel Dilution of Engine Oil". The first few oil samples from new, or newly rebuilt engines often contain elevated concentrations of fuel. The elevated concentration of fuel in early oil samples can be normal.

Coolant Contamination

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Coolant can contaminate engine oil through leaking cylinder head gaskets, water ferrules, cracked cylinder heads, leaking water pump seals, cracked liners, leaking heat exchangers, leaking fuel injector seals and other sources. Coolant in the engine oil can create a thick sludge capable of blocking oil passages and clogging oil filters. Such substances can also reduce oil lubricating properties and act as oxidation catalysts. Oil contaminated with coolant tends to undergo an increase in oil viscosity and levels of K, Na, Cu, Si, Mo, B, Fe, and Al are often elevated along with Pb. Refer to Troubleshooting, RENR5622, "Oil Contains Coolant".

Oil Deterioration and Soot Contamination

Oil oxidizes naturally with time in service and the oxidation process accelerates with high temperatures. For these reasons, oxidation is often associated with long OCIs and/or high temperature operation. Oxidation results in oil thickening, formation of resins, piston deposits, loss of lubricating qualities, and accelerated wear. Highly oxidized oil can leave a honey-colored residue on crankshaft journals. Likelihood of oil filter plugging, filter bypass, and exposure of engine bearings to debris increases with increasing oxidation.

As acids of nitrogen and sulfur form in the engine oil, these acids break down the additives in the oil and accelerate the oxidation process. These acids also create a corrosive environment where lead from engine bearings can leach into the oil.

Table 2 lists factors related to the proper chemistry of diesel engine oil and certain guidelines for monitoring those factors.

Soot is a product of unburned fuel and is produced by all diesel engines. Soot is an abrasive that becomes more damaging to engine components if soot particles are allowed to agglomerate to form larger particles. All diesel engine oils contain dispersants to keep soot particles from sticking together. When engine oil is contaminated with soot, abrasive mechanical wear accelerates. Soot tends to be produced more readily in engines operating at high altitudes and/or having lower than optimal boost pressure. Soot is one of the reasons that recommended oil change intervals for products operating at high altitudes are reduced relative to the oil change intervals of similar products operating at low altitudes.

Illustration 10	g03403376

Oil deterioration and accumulation of soot often results from broken rings and/or worn liners that allow excessive blowby. Refer to Special Instruction, REHS7857, "Testing for Excessive Cylinder Blowby in 3500 Engines" for guidance in identifying cylinders plagued with broken rings and/or worn liners.

Resolve and Proceed