Finding black drips under your ATV can be worrying. The best you can hope for is a leaking drain plug, so I guess maybe we’re getting lucky here.
So why does the ATV oil drain plug the leak? The top 3 reasons an ATV drain plug leaks oil include:
- Missing plug washer
- Worn out crush washer
- Over-tightened plug
In this post, you’ll learn why your ATV oil drain plug (also known as a bung) leaks oil and what you can do to fix it today.
After an oil change, it’s always good practice to replace the oil plug gasket, in many cases that’s a washer. I’ve been a mechanic for more than twenty-five years, and I’m plenty guilty of reusing the same oil plug washer when needs must, but doing so simply won’t guarantee a dry pan.
An untreated weeping oil plug, as you know, coats the underside of your bike in oil, and airflow pushes it back ways coating the rear end in a slick. A leak is irritating but could also be a safety issue, as oil could contaminate the rear brakes and tires, and road surfaces.
The other glaringly obvious hazard is running out of oil and killing the motor. You are absolutely correct. This oil leak needs to be fixed.
1 Missing Oil Drain Gasket
A missing gasket (washer or o-ring seal) is a common mistake to make, you’re changing the oil, and the old gasket drops into the waste oil, either unnoticed or forgotten. Either way, the result is a wet pan. But as you already know you should in theory fit a new gasket whenever you remove the oil drain.
The simple fix here is to fit a new gasket. That will of course mean draining the oil again, a pain in the ass I know. If your oil is fresh and you want to save it, be really sure the underside of your bike is clean before dropping the oil into a pristine container.
Crap falling into the oil is a BIG NO-NO, it could damage your engine.
2 Worn Out Oil Drain Gasket
A worn-out oil drain gasket is a common issue. As said, in many cases oil drain gaskets are reused over and over and simply wear out. The type of gaskets used to seal oil pan drains vary. The three most common oil drain gasket types include:
- Rubber O-Ring seal
- Crush washer
- Flat washer
The rubber O-ring seal slips over the drain bolt and interfaces with the oil pan and creates a seal. This is a very popular type of gasket and is reuseable but is susceptible to damage. Typically a seal might last three or four oil changes. Replacement O-rings can be bought over the counter at any good parts store, but the o-ring rubber is special it needs to be oil resistant, most rubbers aren’t. Bringing your oil bung with you to the parts store will mean a perfect fit, I’d buy dozen while you are there.
The crush washer is one of the most likely gasket types to leak and that’s because it’s one-time use deal. As its name suggests, the doughnut-shaped ring washer is crushed as the plug is tightened. This creates a tight seal but using it a second time risks a leak.
A flat washer made from soft metal such as copper or alloy washers is the last of our common gasket types. They are the most forgiving but obviously wear out too. Copper and alloy are chosen as their soft metals conform to the plug and pan faces creating a perfect seal.
Mechanics hack for pan leaks
It is common practice to use pipe dope in some situations and in a pinch a mechanic may use pipe dope on the oil drain bolt. Pipe dope is a liquid sealer that prevents oil from leaking through plug threads.
Over-tightening oil drain plugs are the cause of many an oil leak problem, and like all young apprentice mechanics, I was guilty of that and a lot worse. Over-tightening any of these washers may cause them to leak or worse strip the oil pan threads. Rubber O-ring seals are especially susceptible to splits or pinches.
Using the correct torque spec on the oil pan is important, most pans are alloy, which is a soft metal and easily damaged if overtightened. A torque wrench would be nice but isn’t necessary provided you have a feel for what’s tight. Typically oil drain bolts are M14 and are tightened to about 17 ft-lb (23Nm).
All manufacturers will have their own torque speck for the plug, but you really only need to use common sense. The more you work on your bike, the faster you’ll develop a calibrated thumb.
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- About the Author
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John Cunningham is a technical writer here at ATVfixed.com. He’s a Red Seal Qualified Service Technician with over twenty-five years experience. He’s worked on all types of mechanical equipment, from cars and trucks to ATVs and Dirt bikes.