Hornet2008
Well Known Member
Have been looking at this and thinking it should be screwed down and split pinned. It is aft of #3 piston. Am I right to do this or is it a redundant part?
Van's Air Force
Don't miss anything! Register now for full access to the definitive RV support community.
Lycoming relief valve???
- Thread starter Hornet2008
- Start date
BruceEicher
Well Known Member
Isn't that your oil pressure adjustment?
N941WR
Legacy Member
Yes, it is. Don't touch it until you run your engine and see how your oil pressure reads
I didn't sleep in a Holiday Inn last night (for the first time in ten days....), but I DID just get home from Lycoming school!
That is perfectly normal the way it is - if you have to adjust oil pressure (you probably won't), then you'd put a wrench on that nutm which is split-pinned to the shaft, and turn it.
Interesting fact - assuming a good pressure gauge that doesn't drift, Lycoming says that the cruise oil pressure in a particular engine shouldn't vary more than 1 psi between new and TBO - if it does, something has plugged or broken, and should be investigated.
That is perfectly normal the way it is - if you have to adjust oil pressure (you probably won't), then you'd put a wrench on that nutm which is split-pinned to the shaft, and turn it.
Interesting fact - assuming a good pressure gauge that doesn't drift, Lycoming says that the cruise oil pressure in a particular engine shouldn't vary more than 1 psi between new and TBO - if it does, something has plugged or broken, and should be investigated.
I don't have an adjustable version on mine, but I am curious what keeps the threaded adjustment bolt from backing out? I would assume that a jam nut would be required to keep it from backing out over time.
Larry
Great question... Wondered that myself for some time now. Mine is non adjustable and after 350 hrs the psi in cruise has dropped 5 psi....oil samples detect no issues. Aerosport claims normal and add a washer per 5 psi. Your thoughts?
alpinelakespilot2000
Well Known Member
It sounds like there are two competing possibilities for how oil pressure is adjusted. One says turn the pinned nut, the other says add a washer. Anyone care to elaborate?
Oil Pressure Adjustment
There are two different types of caps on the oil pressure relief valves. One is adjustable as the one pictured in this thread. Screw it in to raise oil pressure. The second is just a cap without an adjusting screw. You have to screw the cap off. Inside is a spring, a steel ball that looks like a ball bearing, and a stack of washers. Add washers to raise pressure. By they way the ball fits into a machined surface inside the crankcase, the spring on top of it, and washers on top of the spring to add or reduce spring tension on the ball. If you remove the cap be sure to lubricate the threads. It is aluminum and the crankcase is aluminum also. It will gall in a heart beat! I have a data point on that.
There are two different types of caps on the oil pressure relief valves. One is adjustable as the one pictured in this thread. Screw it in to raise oil pressure. The second is just a cap without an adjusting screw. You have to screw the cap off. Inside is a spring, a steel ball that looks like a ball bearing, and a stack of washers. Add washers to raise pressure. By they way the ball fits into a machined surface inside the crankcase, the spring on top of it, and washers on top of the spring to add or reduce spring tension on the ball. If you remove the cap be sure to lubricate the threads. It is aluminum and the crankcase is aluminum also. It will gall in a heart beat! I have a data point on that.
Relief Valve
There are actually three different types. The type shown which is adjustable by turning the nut and two different styles that are adjusted by adding or removing washers.
Regarding the op picture, I cannot see a pin in the picture. The castle nut should be pinned to the shaft.
There are actually three different types. The type shown which is adjustable by turning the nut and two different styles that are adjusted by adding or removing washers.
Regarding the op picture, I cannot see a pin in the picture. The castle nut should be pinned to the shaft.
scsmith
Well Known Member
safety-wire it
My oil pressure drifted down kinda low, so I tightened the adjuster nut a few turns, and it was good. Then a few weeks later, the oil pressure was low again. So I tightened the nut some more. This cycle went on for over a month. Then when I tightened the adjuster the last time, I safety-wired it. Haven't had to touch it since.
In my case at least, there was not enough friction on the adjuster nut to keep it from backing out again after I tightened it. I had never seen one safety-wired, but it sure solved the problem for me.
My oil pressure drifted down kinda low, so I tightened the adjuster nut a few turns, and it was good. Then a few weeks later, the oil pressure was low again. So I tightened the nut some more. This cycle went on for over a month. Then when I tightened the adjuster the last time, I safety-wired it. Haven't had to touch it since.
In my case at least, there was not enough friction on the adjuster nut to keep it from backing out again after I tightened it. I had never seen one safety-wired, but it sure solved the problem for me.
skylor
Well Known Member
OP Adjuster Movement
I experienced the exact same thing on my IO-360, and I safetied it as well after it happend. No problems since (in 450 hours).
Skylor
I experienced the exact same thing on my IO-360, and I safetied it as well after it happend. No problems since (in 450 hours).
Skylor
I've had a dozen different "airport guys" tell me that I need to tighten that nut down and safety wire it. None seem at all convinced when I tell them that it is correct as is, and typically walk off shaking their heads at the folly of it all.
Andy
Look closely...on mine, there is what appears to be a roll pin inserted (and only somewhat visible) through the castellated nut and the threads.
I'll bet you have that, too, but it's just not very visible.
ETA: although it's hard to see, in my copy of the Direct Drive Overhaul Manual, there are 3 possibilities shown in Figure 7-1: Oil Relief Valve Plug (Field Conversion), Oil Relief Valve Assembly (Non-adjustable), and Oil Relief Valve Assembly (Adjustable). The Adjustable version has a part, labeled #15, Spring Pin which goes into parts #14, 3/8-24 NF-3 Nut and #10, Oil Relief Valve Screw.
Just FYI.
Last edited:
celstar
Well Known Member
Low oil pressure
A good friend of mine is in Fredericksburg picking up a new to me RV-3B and noticed pretty low oil pressure of 47lbs on the cruise over. Around 200 hours on a rebuild from lycon. But engine was pickeled for a long time. Will be looking at the pressure relief valve being stuck tomorrow morning but if he needs to dig deeper any recommendations of a A&P at Fredericksburg ?
A good friend of mine is in Fredericksburg picking up a new to me RV-3B and noticed pretty low oil pressure of 47lbs on the cruise over. Around 200 hours on a rebuild from lycon. But engine was pickeled for a long time. Will be looking at the pressure relief valve being stuck tomorrow morning but if he needs to dig deeper any recommendations of a A&P at Fredericksburg ?
Why not connect a manual pressure gauge to confirm pressure before making any adjustments?
Robert Anglin
Well Known Member
New style
You have the newest type of oil pressure valve adjuster. You should go by the book numbers for the pressure setting and yes there are a couple of different high end reading being put out these day, but I don't need to get into that one. The old timers will tell you that when you have some time on your engine to set it at 60psig at 1400 RPMs when the oil is up to 100-115*F. If it drifts as the engine get older just set it up again to the same mark. It well lose a little over many years but only a little. You can put a drop of Torque seal on the threads if you what to see if it has backed off on the adjustment, but most of them are pinged or have self locking methods built in to them.
You have the newest type of oil pressure valve adjuster. You should go by the book numbers for the pressure setting and yes there are a couple of different high end reading being put out these day, but I don't need to get into that one. The old timers will tell you that when you have some time on your engine to set it at 60psig at 1400 RPMs when the oil is up to 100-115*F. If it drifts as the engine get older just set it up again to the same mark. It well lose a little over many years but only a little. You can put a drop of Torque seal on the threads if you what to see if it has backed off on the adjustment, but most of them are pinged or have self locking methods built in to them.
Most likely causes of low oil pressure:
failing sender
failing oil pump
weak spring on oil pressure relief (or mis-adjusted)
A leak
Worn bearings (Highly unlikely due just to sitting to sitting dormant)
blockage in oil cooler circuit (if low oil pressure occurs only at oil temps >180)
Pressure relief can't really get stuck open. It is a ball that is held against a spherical flange by a spring. In theory debris could prevent it from closing, but would take something bigger than 40 or 80 microns (screen rating) . It is directly downstream from the filter/screen and debris here is unlikely unless it had been opened up just before the problem appeared. having the screen housing off could allow debris in if someone was careless.
Larry
Last edited:
celstar
Well Known Member
Here is what we have
When airplane is first started oil pressure is good in the mid 80s, as it warms to 100 degrees goes down to around 70s and in cruise goes down to mid 40s and fluctuates from 39-45. Fixed Cato prop and aeroshell 50 weight. EI pressure, temperature gauge and temperature is steady around 170. Any ideas would be appreciated .
When airplane is first started oil pressure is good in the mid 80s, as it warms to 100 degrees goes down to around 70s and in cruise goes down to mid 40s and fluctuates from 39-45. Fixed Cato prop and aeroshell 50 weight. EI pressure, temperature gauge and temperature is steady around 170. Any ideas would be appreciated .
