Community Member Credit: Eddy

In working on my Gen3 VQ35DE for 4thgen Maxima, I ordered a new OEM Upper Oil Pan. The brand new pans do not come with the oil cooler pressure relief valve, so I ordered one. However, if you decide to use your old greasy upper oil pan, this is a good part to replace to avoid any issues with oil pressure. This is often overlooked. Read the below for more insight into this.

Part Number: 15241-43U0A
Price: $9.00-$10.00

What does it do?

The oil pump maintains oil pressure to lubricate internal components. Most oil pumps are positive displacement pumps, which deliver more oil than an engine needs. To address this, there’s a pressure relief valve located at the oil pump outlet. Its purpose is to open when engine oil pressure reaches a certain value. A problem with the pressure relief valve can cause damage to the engine oil filter and to the engine itself.

Under normal pressure conditions, the oil pressure relief valve is forced down against a spring. As a result, oil goes directly through the pump to the engine. As oil pressure created in the system increases, the valve’s piston is forced against the spring causing it to open. This allows oil to flow back into the crankcase preventing excessive oil pressure. The spring tension of the relief valve determines the maximum oil pressure.

There is no sure way to prevent relief valve failure. In some cases, the valve just wears out over time. However, regular oil changes help prevent sludge and varnish build-up, both of which can cause the valve to stick. Changing your vehicle’s engine oil according to the maintenance schedule is the best way to prevent relief valve problems.

The pressure relief valve can be yet another cause of low oil pressure if the valve sticks open or is held open by a small piece of debris. The relief valve is designed to limit oil pressure as engine speed increases. The valve opens when the pressure reaches a preset value (typically 40 to 60 psi). This vents oil back into the crankcase and limits maximum oil pressure in the engine. The reason for doing so is to prevent oil pressure from reaching dangerous levels. Too much oil pressure can be just as bad as too little because excessive pressure can rupture the oil filter or even blow out pressed-in oil galley plugs in the block.