Bleed an Oil Heater

A Step-by-Step Guide to Bleeding an Oil Heater

You pushed the heater reset button and made sure you had fuel oil. But the heater still won’t start. Do not worry. Before calling the heating contractor or inquiring about a new oil heater, check the fuel source and ensure there is no air in the oil line going to the heater. Running out of oil or running out of oil can cause the oil heater not to start even after you have a full oil tank. You might just need to bleed an oil line to get the heater to start up again.

Preparations for venting the heater

Turn off the heater before attempting any work on the oil pump.

Locate the bleeder valve on the oil pump near the oil line to the heater.

The screw is usually a small grease fitting that resembles a screw.

Place a small bucket or tub under the grease fitting.

The bucket will catch the oil that squirts when bleeding the oil heater. If the bolt is in a place where it’s impossible to place a bucket or small tub underneath, use a flexible tube just big enough to fit over the grease fitting. Place the pipe over the grease fitting and guide it to where the tub or bucket will fit.

Bleed the heater

Use a small arcuate wrench or pliers to loosen the grease fitting slightly.

Make sure the grease fitting stays on the pump and is loosened just a little bit, so it doesn’t fall out when you bleed the heater.

Press the heater reset button to turn it back on.

When the heater starts sucking in the oil, air and oil will squirt out of the grease fitting. Leave your pliers or wrench on the grease fitting so you can tighten it. This will also ensure that the grease nipple stays in place if you loosen it too much. If the heating cycle ends before the air and oil have been squirted out, you must press the reset button to allow the bleed to continue until all air is purged from the line. Some heaters have a locking system, so you can’t use the reset button more than once or twice. In this case, you can override this system by holding the reset button until the heater kicks back on.

When air no longer comes out of the line and oil flows out steadily, tighten the grease fitting again.

Be careful not to overtighten it. Replacing a stripped grease fitting can be a very expensive proposition.

Keep the heating on.

It should now run normally with no problems. Next time it doesn’t restart, check for air in the oil line and repeat the process. You might not have been able to get all the air out the first time, or the oil line might have been blocked by dirt.

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About the Author


Fernando James

James has offered expert financial insight at CouponAnnie since 2020. As a freelance writer, he has been published in a variety of prominent publications. He's been featured on the Washington Post and Financial Planning Magazine, and has been quoted by Money Magazine, Retailmenot, and more.