PSA: That weird oil pressure drop on cold starts might be your relief valve sticking

Spent 4 hours last Tuesday chasing a low oil pressure warning on a Cessna 172 that only happened first thing in the morning. Replaced the gauge, swapped the sender, even pulled the filter looking for metal. Finally found the relief valve plunger had a tiny burr on it from a previous rebuild. Only took me 30 seconds to stone it smooth after I figured it out. Anyone else run into stupid little stuff like that that eats half your day?

2 comments

2 Comments

aaron_ellis4225d ago

Honestly, the first time I had to deal with a sticking relief valve was on a 1972 Chevy pickup I had back in high school. Took me damn near a full Saturday to figure out why the oil pressure would spike then drop to zero on cold mornings. I replaced the pump, cleaned the pan, even swapped the oil to a heavier weight. Finally pulled the valve cover and noticed the plunger had a little lip worn into it from years of sitting. A piece of 600 grit sandpaper fixed it in under ten minutes. Still makes me mad thinking about it. Seems like every time you assume it's something complicated, it ends up being the dumbest little detail.

claire6425d ago

Oh man, that's the worst feeling, isn't it? Idk why but those stupid simple fixes always seem to take the longest to find. Like one time on an old riding mower I had, it was bogging down and dying whenever I went up a hill. I rebuilt the carb, changed the fuel filter, even checked the compression. Turned out to be a little piece of plastic from the gas cap vent that had fallen into the tank and was blocking the pickup tube. A pair of tweezers and thirty seconds fixed it after I'd spent probably four hours on everything else. It's like your brain just skips over the easy stuff because you're so sure it has to be something more complicated.

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