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May 2003

Technical InformationTechnical Information

Diagnosing Filters With CollapsedCenter Tubes or Elements

When a co lla pse d filter element is disco vered, thenatural tendency is to assume something is wrong

w ith the filter itse lf (Figure 1). G ene rally, this is not thecase, but is usually a symptom of problems elsewherein the engine.

Automotive engines incorporate a by-pass valve acrossthe inlet a nd outlet of the full flow filter, w hich s ervesto by-pass oil around the filter if its restriction becomesexc es sive (Figure 2). The b y-pa ss flow circuit insures oil

flow to the e ngine when there is a significa nt res trictiona cross the filter due to loa ding or cold s tart cond itions.

Typica lly, engine ma nufa cturers des ign by-pa ss valvesto open at a filter differential pressure of 10 psi (70 KP a ), w ith some opening a s high a s 30 psi (206k Pa ).So me engines have the by-pas s va lve mounted in theengine block, while others loca te the by-pa ss valve inthe filter.

Automotive lube oil filters are designed to withstanddifferential pressures significantly greater than thoseexperience d under normal operating co nditions withoutcolla psing. Therefore, when a n element has co llap sed ,it is usua lly the result of a s ticky o r otherwise ma lfunc-tioning b y-pas s va lve.

In some instances, a sticky filter by-pass valve aloneis not e noug h to c olla ps e a filter. The o il press ure reg u-la ting valve may also stick, resulting in increas ed pres-sure and flow through the filter. Although this conditionma y be only mome ntary, it ca n q uickly co llap se thefilter center tube if the by-pass valve fails to relievethe press ure.

A co lla pse d filter ca n lead to a los s of filtra tion a nd o ilflow to the engine; there is the possibility that interiorpa rts of the filter or filtering m a teria l may b e torn a wa yand move into the fluid sys tem a nd interfere w ith theoil flow.

The ma lfunction of the b y-pas s a nd o il press ure regu-lating valves and the subsequent collapse of the filtermay not ca use noticea ble dama ge but at times it ca nresult in a ca tas trophic failure to the eng ine; s eizure o fa piston or of rod or main crankshaft bearings.

The ma lfunction of b y-pas s valves a nd regulating valveshas b een traced to:

S ticky surfaces ca used by cold, highly visco us oil;

Oil contaminated by excessive condensat ion, coolant ,or oxida tion;

Neglect extended o il drain and filter chang eintervals;

Ca rbon grit that temporarily jams a va lve;

S udden ac celeration of the engine with any of the

ab ove c onditions.

Disc overy of a co lla pse d filter ca lls for inspec tionof the filter by-pas s valve and the pressure reg ula torvalve and a review of the engine and its performanceand maintenance history.

Figure 1 Figure 2 Normal Pressure

Normal

Oil Filter

Collapsed

Oil Filte r

Bearings

Spin-On Filter

By-Pass

Va lve

(Closed Under

Normal Conditions)

PumpExcess Oil

Pressure Regulating

Valve in Open P os ition