The Role of the Oil Filter Bypass Valve in Engine Protection

The oil filter bypass valve, also known as a pressure relief valve, is a component that plays an important role in preventing engine damage caused by oil starvation. It's typically built into the filter or located in the oil filter housing, and its main function is to protect the engine from potential damage when the oil filter becomes clogged or restricted. It's a safety feature that ensures the engine always gets oil, even if the filter is not functioning optimally. Without the bypass valve, you could face serious engine issues if the filter gets blocked by dirt, sludge, or debris.

How the Oil Filter Bypass Valve Works

The oil filter bypass valve opens when the pressure across the oil filter exceeds a certain threshold. This happens when the oil filter gets clogged and can no longer allow oil to pass through efficiently. A clogged oil filter restricts the flow of oil, which causes a buildup of pressure behind the filter. This pressure triggers the valve to open and allows oil to bypass the filter entirely and flow directly into the engine. It ensures that the engine still receives lubrication, albeit without filtration. This is a temporary solution until the filter can be replaced. The valve will close again once the pressure normalizes, and the oil starts flowing properly through the filter again.

The bypass valve is typically set to open at a pressure between 8 and 15 psi, depending on the engine and the filter design. This ensures that oil can still circulate if the filter gets clogged but prevents the valve from opening too soon. It’s worth mentioning that the bypass valve doesn’t open just because you accelerate. However, if the filter is already partially blocked, high RPMs or sudden acceleration can spike oil pressure enough to trigger the valve. The valve responds to pressure, not directly to acceleration, but they’re related when it comes to oil flow.

What Happens If the Valve Fails?

If the valve is stuck open, unfiltered oil will flow into the engine, which can lead to rapid wear. If it’s stuck closed, oil may not circulate properly, leading to a lack of lubrication and increased engine friction. Symptoms of a bad oil filter bypass valve include oil pressure problems, engine knocking, or unusual noises. You may also see a drop in oil pressure, especially at high RPMs.

FRAM Oil Filters

FRAM oil filters are engineered to meet or exceed OEM specifications, ensuring that your engine gets the protection it needs throughout the recommended oil change interval. Our most durable filter, the FRAM Synthetic Endurance™ oil filter, is built with a bypass valve that features a precisely calibrated coil spring and a glass-fiber-reinforced nylon poppet. What makes this important is the durability and consistency of the valve's performance. The glass-fiber reinforcement in the poppet adds strength, so the valve operates effectively even under high pressure. The precisely calibrated coil spring ensures the valve opens at the correct pressure, which is crucial to maintaining the right oil flow when the filter gets clogged. It’s a design that helps maximize engine protection without sacrificing filtration quality.

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