Foreign Service

Motor,  Feb 2004  by Marinucci, Dan

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When entering into battle with 'frozen' fasteners, Dan has discovered, advance preparation and the element of surprise may be your best allies.

Some technicians rarely see corroded, frozen fasteners because they live in relatively dry, sunny regions of the country. But for thousands of others, inclement weather and road salt make these things common occurrences. This month I'll discuss loosening some stubborn fittings that might otherwise fool you and recommend ways to prevent repeated problems.

For instance, fuel filter fittings on a variety of popular Japanese vehicles can be deceptively tight as well as difficult to reach. Many Japanese vehicle specialists have told me the fuel Biter located on the right-side frame of many popular 1990s Toyota trucks are the worst. Even techs who work in the Sun Belt report that loosening the fittings on an original Toyota truck filter can be a hassle if you don't work smart.

You'll also encounter high-volume Toyota cars such as Camrys and Corollas on which the fuel Biter is hidden relatively low near the driversside inner fender well. What's more, lots of common 1990s Honda Accords have a fuel filter mounted way down on the driver's side of the firewall. The locations of these Honda and Toyota filters make it difficult-if not impossible-to get a standard flare nut Biting wrench onto the lower fuel Biter Btting. (Note that many techs know a flare nut wrench as a line wrench.)

Sadly, many of these cars and trucks are finally showing up for their first fuel Biter replacements because the original Biters are so dirty they're causing lean driveability symptoms. So don't assume the fittings have been opened up already because you can't be sure. Simply soaking them repeatedly with penetrating oil ahead of time may not suffice. Furthermore, the service writer up front usually isn't aware enough to get the vehicle in the night before so you can soak suspect fasteners overnight.

Sources agree that the very least you should have is a set of flare nut crowfoot wrenches. Although 14mm is a very popular size for fuel line fittings, you'll likely use other sizes on everything from other fuel system fittings to refrigerant, power steering and brake line fittings. The crowfoot flare nut wrenches we've seen come in conventional 3/8-in. drive, so you'll also need a long 3/8 extension and breaker bar. Use the long extension to position the crowfoot flare nut wrench onto the lower fuel Biter fitting. Hold the drive end of the breaker bar with one hand and give the breaker bar handle a quick, hard yank with the other hand. With some luck, this will loosen the fuel filter fitting easily.

Like loosening any other frozen fastener, you want the mechanical advantage of applying the loosening torque to the fastener as directly and suddenly as possible. Therefore, I prefer a breaker bar to a ratchet in this situation because there's less "give" in the head of a breaker bar.

Depending on the filter location and the tightness of die fittings, many technicians resort to an impact gun to deliver that crucial first shot of loosening torque to the frozen fitting. Photo 1 on page 8 shows the typical setup they prefer, including a 3/8-in. drive impact gun, an impact extension and the appropriate flare nut crowfoot wrench. On vehicles such as the Toyota trucks, you'll probably also need an impact universal due to the limited working space near the fuel filter (see photo 2).

Sources emphasize that the trick is to get the flare nut crowfoot wrench securely in place on the fuel filter fitting. Then squeeze and release the impact gun trigger as quickly as possible. All you want from that gun is one brief brapp! Once the fitting is loose, you can use your fingers or the basic tools to undiread it completely. This has saved many techs from having to cut out the original fuel filter and either splice or replace fuel lines.

We technicians call this approach a necessary evil. However, tool people call it improper and potentially unsafe tool usage. Some Toyota specialists I know have done this several times per month for years without incident. But flare nut crowfoot wrenches aren't made for use with an impact gun, so "impacting" one voids any warranty on it. Plus, the sudden, powerful jolt from an impact gun could eventually shatter a standard crowfoot wrench. Conclusion? Use this approach at your own risk.

At the very least, take the following precautions if you do use an impact gun as described. First, open the gas cap and safely depressurize the fuel system beforehand. Second, wear safety glasses as well as a full-size shatterproof face shield like the kind you're supposed to use when operating a bench grinder. Never count on just one or the other in this situation. Third, sources agree that a quick jolt from a 3/8-in. impact gun is all you need; don't use anything more powerful. Fourth, always use an impact extension and be sure the flare nut crowfoot wrench is flat and secure on the fuel filter fitting.

Finally, treat the fuel filter fittings as if you're the one who'll be loosening them next time, especially if you're in snow-and-salt country. Lubricate the threads of the fuel line fittings with something that won't contaminate the fuel system and/or the connection. Then retighten the fittings to spec by hand, start the engine and carefully check for fuel leaks before signing off on the vehicle.