oil pressure problems

W

wayne

New member
Oil pressure on my 8KCAB newly overhauled AEIO 320 drops from 85 to 70 After the oil fully warms up, about 2-3 minutes into the flight (with a new oil relief spring). When oil pressure drops it drops very quickly in 2 to 3 seconds. Do's that sound normal? I never have seen that drop before when the engine was an IO 320. I'm running 100 mineral oil. Could it have something to do with the new christen oil system?
 
read this:

https://www.lycoming.com/content/understanding-oil-flow

its probably the vernatherm opening. which is different from the pressure relief valve.

bob
 
Hi Bob, Thank you for all your help. I talked to Penn Yan Aero and Lycoming engine and they said its not the vernatherm but it still makes sense. The engine did run a little cold. Had to put a plat on cooler to get temp up to 180. I will ask my mechanic to check that next. Thanks again. Wayne Cotton
 
I don't think it could be the Vernatherm, it extends SLOWLY as the temp rises to close the cooler bypass port and force oil to go through the cooler.
I would be more inclined to think maybe the gauge has some kind of a problem? Also even though the oil P spring is new, there I are 3 or 4 different springs part numbers that can be used to get the desired pressure, as well as adding up to 9 washers under the spring (on the regulators that don't have the external screw to adjust).
I can't see any way the Chisten system could be a cause in level flight.

Remember to let us all know what the cause and fix is, that way we all learn.
Bill B
 
if it was the vernatherm, wouldnt the pressure drop when the valve bypasses the cooler and rise when the pump had to also push the oil through the cooler, like in a very cool running engine when you would throttle back after takeoff and the motor cools down ? like with a motor you had to block off half the cooler to get the oil up in the green? not a normal situation i admit but food for thought and consideration in most cases, once the vern routs oil to the coller it never stops until the airplane is sitting in the hangar or at least gliding in to land. but in this case??

time spent trying to figure out the ideosycricities of these motors is not wasted. of course, the first thing to consider is the last thing you changed. but you know, you are a long way from the place where you need to worry about low oil pressure.
 
The problem with the Vernatherm theory is that the oil pressure relief valve is down stream of the Venatherm, and so is the port for the oil pressure gauge. So the oil pressure relief valve would keep the pressure at the level it was adjusted to regardless of a change up stream.
Bill B
 
Ha guys, I don't know what happened. The oil pressure all come in line. 90 on take off, 80 after a few minutes and stayed there through different power settings and 75 at idle. Maybe a ball seated in the Christen oil valve? Its an all new system including a new oil gauge. If it stays I'll never know. I'm cautiously optimistic.
 
Lycoming’s manual for the Aerobatic engines has a troubleshooting guide plus descriptions of normal behaviour at https://www.lycoming.com/sites/default/files/AEIO-320-360-540%20Oper%20Manual%2060297-21.pdf
 
Just to clarify, it's not really a relief valve, it's a pressure regulator valve, so it modulates to keep the pressure at whatever it is set at.

Thanks for the update, happy all is well.
Bill B
 
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