The engine oil pressure relief valve regulates oil pressure when the oil is cold or hot ?
What’s the engine? I never thought that oil temp would matter
Cold oil, bypass valve. Protects oil filter from bursting. Relief valve, is for everything else. Smaller surface area than bypass and is typically integral to the old gear pumps. The newer gerotor pumps usually have a separate valve hidden somewhere else.
Correct, but to be clear the bypass valve ONLY protects the filter from damage, it does not regulate the actual oil pressure. Many of the Japanese diesels have both built into the filter adapter.
oil pressure relief ( or regulating) valve limits oil pump maximum pressure all the time-hot or cold. some engines have more than one- maybe also an oil gallery relief somewhere ie. old waukesha small 6 and 4 cylinder diesel engines. the filter bypass valve does not regulate maximum oil pump pressure, it should only bypass when the oil is cold and too thick to flow through the filter during start-up. as the oil warms up, and the viscosity changes, more will flow through the filter until it is thin enough for the valve to seat and all oil flows through the filter.
It's just a general discussion. Some people told me that the oil pressure valve only work when the oil temperature is low and it wont when the engine reaches the operating temperatures.
If the engine is worn with excess clearance, or the oil is incorrect viscosity, when the engine warms up then the oil pressure will drop below acceptable limits regardless of relief valve operation. If the oil pressure rises above acceptable limits when the engine is warm, that is a dangerous malfunction somewhere, but I have never seen this happen.