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Troubleshooting Article Archive:  March 2008      
Dirty Jobs:  Hydraulic Filter Assembly Leaks







Wrong way

  Right way
In the aftermath of the bursting of the stock market bubble in the early 2000s, I became a devotee in my spare time of reading what people had to say about investing, on the strength of the idea that a down market might have wiser lessons, being more dearly earned, than an up market.  To learn from other people's mistakes, after all, is at least as good as learning from your own, and less expensive.  Of all the nuggets of wisdom ("Buy low and sell high"), the one that sticks in my mind is, "The stock doesn't know you own it."

This curious phrase was cautionary advice for gullible people who badly wanted, say, four new Jet Skis or a second house, and decided they would invest in the stock market in order to have the money to buy that stuff.  I call it curious because, on one hand, it's plainly obvious that an individual stock doesn't "know" or "care" that its owner badly wants or needs its price to go up; and on the other hand, that such a statement needs to be said at all indicates just how easily emotion can cloud judgment.

I think of that phrase whenever I'm troubleshooting in the dirtiest nether regions of a tow truck, because some similar dynamic is at work in the troubleshooting of dirty or hard-to-get-at tow truck components.  The assembly you're troubleshooting doesn't know or care how dirty your arms are going to get when you work on it, or how hard it is to see or get to.  The nature of the disorder and the nature of the cure remain the same, regardless of how you feel about the accessibility and visibility challenges involved in troubleshooting the assembly.

The hydraulic filter assembly, for instance, is usually underneath the wrecker bed and is often the dirtiest, hardest-to-get-to part.  It often bears a thick coat of grime, so it resembles one seamless piece instead of the manifold part it actually is.  When it leaks, poor troubleshooters tend to mentally gloss over the details of the assembly and blindly start throwing new parts at it.

Instead of glossing over the details of the part, it pays to imagine the part clean and sitting on the bench, and to think about the several completely separate places where oil could leak.  For example, oil sometimes leaks out of the gasket-mating surface between the aluminum filter head and spin-on filter.  Or the spin-on filter itself splits and oil leaks from there.  In either of those two cases, fix the problem by installing a new spin-on filter.

Another common and completely separate leak location is the connection where the aluminum filter head threads onto a pipe nipple or fitting.  Solve that problem by taking it apart, putting generous amounts of liquid pipe dope (never Teflon tape) deep into the valleys of the tapered threads, and tightening the connections good and tight.

When tightening the aluminum filter head onto the pipe connections with pipe wrenches, avoid positioning the two wrenches on opposite sides of the filter head, as tightening across the soft-metal filter head will distort it.  Instead, position the two wrenches next to each other and tighten one connection at a time.