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Technical
Service Bulletin 88-3R2
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Diagnosing Engine Oil Filters With Collapsed Center Tubes
When
a collapsed center tube or element is discovered, the natural tendency
is to assume something is wrong with the filter (Fig. 1). This is not
the case, but is a symptom of problems with internal engine components.
Most engines incorporate within the oiling system a by-pass valve across
the inlet and outlet of the full flow oil filter. The valve is designed
to open and by-pass oil around the filter and/or element when the restriction
reaches its opening pressure (Fig. 2). The by-pass flow circuit insures
oil flow to the engine when there is a significant restriction across
the filter due to plugging or cold start conditions. Typically, engine
manufacturers design by-pass valves to open at a pressure differential
of approximately 10 to 30 psid with some as low as 4 psid (28 kPad), with
some opening as high as 75 psid (500 kPad). Some engine manufacturers
have the by-pass valve located in the filter mounting base on the engine,
while others locate the valve in the filter. Either way, the same purpose
is served.
Oil
filters are designed to withstand, without collapsing, differential pressures
significantly greater than those experienced under normal operating conditions.
Therefore, when a center tube or element has collapsed, it is usually
the result of a "sticking" or otherwise malfunctioning by-pass
valve.
A collapsed center tube or element can lead to a loss of filtration and
oil flow to the engine. There is the possibility that interior parts of
the filter or filter media may be physically displaced and could migrate
into the oiling system interfering with the oil flow.
The malfunction of the filter by-pass valve, as well as the subsequent
collapse of the center tube or element, may not be visually apparent.
However, a catastrophic failure of the engine may result due to the seizure
of a piston, connecting rod, or main crankshaft bearings among other failure
possibilities.
The malfunction of filter by-pass valves and pressure regulating valves
has been traced to:
- sticky surfaces caused by cold, highly viscous oil;
- oil contaminated by excessive condensation, coolant, or oxidation;
- improper oil drian and filter change intervals;
- carbon grit that temporarily jams a valve;
- sudden acceleration of the engine with any of the above conditions.
An oil filter with
a collapsed center tube or element indicates a malfunction within the
system. Inspection of the system and a review of the engine's performance
and maintenance history should be conducted.
For additional information, contact:
Filter Manufacturers
Council
P.O. Box 13966
Research Triangle Park, NC 27709-3966
Phone: 919/406-8817 Fax: 919/406-1306
www.filtercouncil.org
Administered by Motor & Equipment
Manufacturers Association
Revised October 2005
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