Engine: pressure relieve valve

[jbjr]

what are the signs of a pressure relieve valve needing to be replaced?

[53commander]

When mine stuck I had full oil pressure at idle to the point it broke the gauge.

[StudeRich]

If for some reason the "Control Spring" is weak, wrong or missing, you will have low Oil Pressure, but what post #2 said is the more common situation.

They need to be clean and free to move more than Replaced.

[Mike Van Veghten]

Per what StudeRich says, that's only when you should have high pressure, you may have low pressure.
The lower the engine rpm, the less the "over pressure" spring does..! While I haven't done a science project on it, I'd guess the piston is held tight to around 1500 to 1800 rpm, before the pressure starts to build to the point of bleeding off pressure.

In any case, the way springs work, I doubt many actually have weakened to the point of needing replacement in many engines, though...sure, no doubt some have. As has been said, it's more likely not keeping the system clean and having the piston stick in place and causing overly high pressures.

Mike