In the Shop: Put an End to Ooze

August 24, 2012 07:26 PM

Fixing leaks on farm equipment can be a challenge. On a complex valve block or hydraulic connection with multiple fittings, it can be difficult just to pinpoint the source.

To identify the location of a small leak, clean the suspected area with a pressure washer. Blow off excess water, then clean again with electric contact cleaner, brake cleaner or other evaporating cleaner that leaves surfaces dry. Dust the area with cooking flour or planter talc. Fling handfuls of the powder, forcing it into every nook and cranny.

Start the machine and activate every hydraulic function associated with the area. Shut off the machine and examine the dusted components. Even a minuscule drop of liquid will reveal itself, pinpointing the location of the leak.

Once the location is identified, disassemble the component and determine the cause. If it’s a flare-type hydraulic fitting, look for hairline cracks that spread open when the fitting is tightened. If it’s an O-ring fitting, look for a cut or damage. Inspect the mounting groove and surrounding surfaces. Easily diagnosed damage to the O-ring might have been caused by less obvious damage to the fitting.

Repairs to any hydraulic system carry a risk because of the danger of working with oil under high pressure. Special care is necessary if leaks are associated with lifting a tractor’s loader, raising a combine’s feederhouse, or other raising and lowering functions. Block and support the components before repairs.

Use extreme caution when disassembling valves and hydraulic lines—the component might be under pressure and explosively release that pressure if the system isn’t "bled" before beginning repairs.

Gearcase leaks. Leaky gearcases aren’t as risky to repair, but they make up in frustration what they lack in danger. The key to ending gearcase leaks is attention to detail and patience during reassembly.

First, throw away any gaskets salvaged during disassembly. Even if a gasket looks good, it should not be re-used. That’s because when a gasket is installed, it is crushed and thinned. A used gasket might look fine when removed, but its surfaces are microscopically marred and its thickness reduced enough to limit its ability to mold to new surfaces.

Even a new gasket can leak if the mating surfaces aren’t properly prepared. Use a scraper to remove all traces of old gasket material or adhesive. Professional mechanics use Scotch-Brite–type sanding pads on air-powered tools to remove stubborn glue and gasket material. An electric drill and Scotch-Brite–type pad, or patient hand-sanding with an emery cloth, can accomplish the task if air tools aren’t available.

Most agricultural gearcase gaskets are installed "dry." Adhesive can be applied to one side of the gasket to hold it in place during assembly. Apply a thin coat and let it slightly dry before installation. "Wet" adhesive can lubricate gaskets and allow them to slide out of place, distort and squeeze into bolt holes and passages when the bolts are torqued.

Don’t confuse gasket adhesive with gasket sealant. Adhesives are designed to hold gaskets in place during assembly. Sealants, whether traditional gasket sealer or modern silicone sealant, are for use with or without gaskets to fill deeper imperfections in mating surfaces.

If used with a gasket, sealant should be applied to both sides and the gasket installed "wet." Use gasket sealant with care. Just like wet adhesive, it can lubricate gaskets so they slide out of place during installation, and blobs of excess sealant can enter bolt holes and passageways. Use gasket sealant only when mandated for specific repairs by the machine’s manufacturer.

Many farm equipment gearcases and gearcase covers now come with rubber gaskets or O-rings. It’s best to replace these rather than re-use them. Unless specified by the equipment’s manufacturer, do not use gasket sealant or silicone sealant when installing rubber gaskets or O-rings. As we’ve already seen, wet adhesive and gasket sealants can do more harm than good—encouraging rubber gaskets and O-rings to squeeze out of place when components are tightened.

Cool Tool

Scotch-Brite–type abrasive pads come in a variety of sizes and degrees of abrasive quality. Mount a pad on a mandrel, then install the mandrel in an electric drill or air-powered tool to remove stubborn gaskets, adhesives or sealants.


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