Time for an overhaul

Max Kvidera | November 02, 2010

Oil analysis

By having an oil analysis done – at $10-$20 per sample – at every change interval, you can monitor metal concentrations and other deposits that could harm your engine. If metal particle levels are too high, this could signal a failure of the rod, main bearings or cam bearings, says Danny Long, Mack Engine product manager.

“An oil analysis will also indicate if there is a high concentration of fuel or antifreeze mixed with the oil,” he says. This could indicate failing piston rings or excessive cylinder liner wear.

Oil analysis works best if it’s done over the long term so that samples can be compared, says Dan Arcy, OEM technical manager at Shell Lubricants. If you consistently see iron, lead and copper particle readings at a low level, you’re OK. But if something goes awry and a contaminant appears, the reading will increase markedly. “The sooner you catch it, the better off you are,” Arcy says. “If you do analysis infrequently and find something, you won’t know how long the problem has existed.”

Maybe the air cleaner isn’t seated properly, allowing unfiltered air into the engine. That will show up in an oil analysis, Arcy says. “If you correct it, you may have lost a bit of life in your engine but you probably haven’t destroyed it.”

Analysis contains extensive information, but doesn’t focus on only one result, says Maria Burcham, a technical adviser with ExxonMobil Lubricants & Specialties. Instead, look at the overall report. For example, low oil viscosity and fuel dilution might signal a fuel injection system problem. Those results plus high wear metals in the sample might indicate troubles with piston rings or cylinder liners. “If your system is starting to fail, you’re going to see multiple indicators that will point you in the same direction,” she says.

Over a long period, the graph of an engine’s oil analysis readings often resembles the shape of a bathtub, says Richard Hassebrock, an engineer at Castrol Lubricants. The first few samples from a new engine might show high levels of wear metals before dropping significantly to a consistently low level. When the engine nears the end of its useful life, the readings might rise again. “Unfortunately, we live in a real world,” he says, and engine wear trends are not always so predictable.

If you choose to collect the oil sample yourself, don’t take the first drops after opening the drain, which are likely to contain debris, says Chevron Global Lubricants Direct Marketing Specialist Jim Gambill. “Let it drain for a few minutes and then take your sample,” he says. And make sure you note the mileage for the lab.

Hassebrock notes that if you’re adding oil frequently, it can sometimes mask oil analysis wear metal readings. He recommends keeping track of how much oil you’re adding and telling the lab. “I’ve had a situation where an engine failed and it wasn’t predicted,” he says.


Crankcase blow-by

As pistons and piston rings wear, they allow more compression and combustion gases to escape into the crankcase and through a rubber blow-by, or draft, tube that runs alongside the engine. As the gas increases because of worn rings or pistons, microscopically tiny oil droplets collect and eventually drip from the tube, which is a cause for concern. You might not notice until airflow blows the dripping oil across the front of the fuel tanks and under the truck. However, this may not happen on 2007 and later engines as oil droplets are filtered out of the blow-by gases before being emitted. Engine shops can test for excessive blow-by.

The pleats of this oil filter revealed metal particles, which in some cases aren’t found in oil analysis.

“The operator will also notice an increased rate of oil consumption,” says Zack Ellison, a customer support director for Cummins. “Instead of going 2,000 to 3,000 miles on a gallon of oil, they won’t make 1,000 miles. They’re starting to have significant wear inside the cylinder kits.”

Also contributing to elevated blow-by could be a leaking turbocharger seal, Ellison says. It will leak into the crankcase down the oil drain tube of the turbocharger. He says a good shop will isolate the turbocharger when troubleshooting blow-by and test the engine. Badly worn valve guides and cylinder heads can also increase crankcase blow-by. “Most of the time if you have a cylinder head or valve guide that’s worn out, you’re probably ready to do an in-frame overhaul anyway,” he says.

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