گیر کردن شیر اطمینان فشار روغن

The relief valve limiting maximum oil pressure, stuck so it can no longer regulate. It is a simple spring-loaded valve whose job is to dump surplus oil back to the sump once pressure reaches its limit, and it fails in both directions.

Stuck open is the dangerous one: oil bypasses continuously and pressure never builds, which reads exactly like a worn pump or worn bearings. A sudden loss of pressure on an engine with no history of wear is worth taking to the relief valve first, since it is a fraction of the cost of the alternatives.

Stuck closed gives excessive pressure, which stresses the filter and seals and can blow a filter's seam or push oil past a crankshaft seal. Debris is the usual mechanism — a particle holding the valve off its seat — so a stuck valve means the oil is dirty, and it is worth inspecting the sump. Confirm pressure with a mechanical gauge before concluding anything, since the sensor is the other explanation.