Non Adjustable Oil Pressure Relief Valve, Looks like? Location?

[Toothcarpenter]

Some help here from you guys, that know. Experimental Bushmaster. Lycoming 0-360 A1F6D One of those single unit, Dualmag, 180hp. Has Oil filter. Does anyone, know how to ident. for me the location of the oil pressure relief valve, versus the vernitherm. I have scoured the web, looking for drawings of the non adjustable valve. Wanting to locate, disassemble, and clean any debris in the seat, and inspect. Warmer day, 20/50 oil, Had been pulling it hard for an hour. Pressure was fluttering. Idle 45-50, and turned up to 2450, fluttered between 70 and 90. So I conclude that pressure is not too low, or too high, Just want to inspect the press. relief valve, and clean. Read something about a sleeve, and changing it. Also how to change from non adjustable to adjustable. Couldn't find any exploded drawing anywhere of the two valve types, and their parts. As stated before, I wish I knew the look and location of the vernitherm and the relief valve on the filter/acccessory case housing. Thanks so much for taking a look at this query for me. Ed

 

[8GCBC]

Right side in the back?

Send pictures of the right side of engine, I'll draw an arrow and send it back

(2) types: 1) washer loaded, 2) screw loaded

 

[tamarack]

Do you mean the vernitherm which controls whether the oil is routed to the oil cooler thus controlling the oil temperature? Or do you actually mean the oil pressure adjustment that controls oil pressure?

The oil can be routed to the oil cooler via two types of controls. One is the vernitherm which actually adjusts a gap between a plunger and a seat by expanding or contracting the plunger in response to the oil temperature flowing past the body. The older kind is a plunger and spring arrangement that controls the oil flow to the oil cooler basically by oil pressure ie. the warmer oil is assumed to be lower pressure so is routed to the cooler. I have never seen a problem with either type of temperature regulating assembly cause fluttering oil pressure. Both of these units are in the accessory case just off of center line to the left side above the magneto.

The oil pressure adjustment, as mentioned earlier by 8GCBC, is on the right hand side of the case in line with the oil gallery that is along the pushrod tubes. You are correct, there are two kinds, either of which can be cleaned or might perhaps lead to fluttering oil pressure.

Have you checked your oil pressure gauge? Is air getting into the oil pump pick-up at the case to sump connection? Did this start suddenly? How many hours on the engine? Constant speed prop?

The folks on this forum will have a wealth of advice for you. Please check back in with more details.

Vickie

 

[Toothcarpenter]

Thanks for your comments. I will try to get a picture. The fluttering came on kind of suddenly. 20/50 oil and I ran it hard so it was quite hot, although the oil temp was just over 200. I was not suspecting the vernitherm, as the cause, and wanting to pull the oil press. relief valve out, or apart, to inspect and clean. Engine is low time. Running great, I am not suspecting bearing failure or mechanical failure at this time. As the engine cooled down, the fluttering diminished, and with 50 weight, it is hardly noticable. I just thought I should identify the pressure relief valve, and inspect it as a possible cause, as well as install another guage temporarily along with the fluttering one, and compare. I got this engine together last fall when it was getting cold, and have run it 100+ hours, in cold weather. (not alaska cold, but Idaho cold) Only last week, did I really get it out and work it hard in warm air. So what I am seeing, may have been there always, and the hotter temps, are making it noticable.. I installed a straight 50 wt, and flew it an hour, and the fluttering in the oil press guage was almost non existent. I am almost positive also, that I did not use any sort of a fitting with a small restrictive orifice on the oil pressure line, to the guage. So I have several things to do, or check. I am lazy, and was hoping the first thing I pulled out of the engine would be the pressure relief valve, rather than something else. Thankyou again, so much for the comments and help.

 

[Steve Pierce]

I would clean the oil pressure relief valve. Had the same problem before and found carbon between the seat and the oil pressure relief valve. Like posted above it is on the right rear of the engine.


Vernatherm.


which goes in this large hole in the oil filter adapter.

 

[sierra bravo]

Like Vickie says, not all Lycomings use a Vernitherm. Mine does not. Interesting that the problem is prevalent with one type of oil.

For reference: http://www.sacskyranch.com/eng18.htm

 

[Cub Builder]

From the Lycoming 76 series manual: Non-Adjustable Oil Pressure Relief Valve. Although the valve is not adjustable, the oil pressure can be controlled by the addition of STD-425 washers under the cap as required (maximum of nine), to increase the pressure. Particles of metal or other foreign matter between the ball and the seat can cause the oil pressure to drop or fluctuate. Therefore, if a drop or excessive fluctuation is noted it is advisable to disassemble, inspect and clean the valve.
--------

Additionally, I majored one of this model engine a couple of years ago that had an oil fluctuation issue (as well as a spauled cam). After overhaul, the oil fluctuation problem was still there. With the help of Lycoming tech support, we finally discovered that the engine had the incorrect ball in the oil pressure valve. It sure looked right, but the new ball fixed the problem. I hadn't replaced the ball on major as the engine only had 130 hrs since the previous major and the ball appeared to be perfect.

-CubBuilder

 

[Toothcarpenter]

Thankyou all. This is useful information to me, and will launch me into looking at it. I'd rather be flying it, than maintaining, but this should not keep me down too long. Sure do appreciate the efforts of those who helped me with pics and info. I now have useful direction, and likely less wasted effort.

 

[Cub Builder]

With regards to the Vernatherm, on my O-320 I normally see a 10 psi pressure drop once the oil temp warms up and the vernatherm is redirecting the oil through the oil cooler rather than bypassing it. The additional resistance routing the oil through the oil cooler will cause the drop in oil pressure. The variance could be more or less depending on the capacity of the oil cooler and the size of the fittings and hoses going to it.

-CubBuilder

 

[8GCBC]

Also, the viscosity of oil drops fast with temperature rise (single grade) which translates in lower PSI .

 

[Toothcarpenter]

Something I have never thought about

Considering the oil pump as the source of oil pumped under pressure, my new question is; Is the oil delivery at the high side, or pressure side of the oil pump, produced in pulses, or as a steady flow. In thinking about the fluttering oil pressure gauge, I originally made the assumption that the oil under pressure was delivered into the system, as a steady flow, under pressure, and that any pulsing had to be from conditions, or devices downstream. That is the assumption I am still making, but now am second guessing myself. If the pump delivers pulses, then one would expect those pulses to be moderated by the passages the oil passes thru, as well as any restrictions or orifices such as the pressure relief valve. If the relief valve is not functioning properly, one would wonder if it is fluctuating or fluttering, or if it is just leaking because of debris, such as carbon, and being close to the origin of the oil under pressure, the oil if pulsing from the pump, may not be pulse moderated by the pressure relief device. I hope this wondering is not clear as mud, and am not so sure it is important, yet in thinking thru the pulsing seen at the guage, I am left wondering what is the source of pulsing, and what are the possible moderating devices or conditions. . If the oil pump delivers pulses, then it is easier to see why smooth operating relief valves, and constriction orifices, in the line to the guage, could be important. I always thought of the lubrication oil, under pressure, barring any low oil or loss of oil condition, being smoothly and seamlessly delivered to all parts of the internal combustion engine. As I sat and watched that needle flutter, I began to wonder what is the source of this pulsing, and what does it take for this gauge to fail, and hot oil to start pumping out from behind the panel. Suddenly an orifice restrictor in the line to the gauge began to make a lot of sense, in prolonging the ability to produce power a bit longer, once a gauge failure and leak was identified by an unhappy right seat pilot (4 place Bushmaster). I once had a nose seal push out on a Lyc 540, due to a plugged crankcase vent, and it didn't take long to empty out the sump. Fortunately I was on downwind when it happened, so was uneventful, other than landing, looking thru the side window, and the cowling hinges never again needed oiling. Once again, thanks a lot for your comments. You guys are super, in graciously dealing with the unlearned. I am really looking forward to meeting some of you all at JC this year. I used to fly brand Xmaule with the 0-540 in those strips. It's a shame to live in Idaho, and not be current in all those strips. Really looking forward to getting into those canyons again, where 60mph seems like 160. You all please be extra careful when defying gravity.

 

[tamarack]

Toothcarpenter,

Your analysis of the effect of oil flow is very insightful. The oil pump is merely two gears more or less sucking up and pushing oil through the system. The oil is pulsed, but theoretically at a frequency that is not significant or noticeable. Leakage in the suction or leakage between the gear teeth or around the gears can disrupt or decrease oil pressure. Losses or leakage is attenuated by higher viscosity oil.

You might examine the oil flow diagram in the beginning of the Lycoming Direct Drive Overhaul manual.

Let us know the results of whatever course of action you try!

Vickie

 

[btracy]

Is it a mechanical gauge? Sometime back there was a thread on fluctuating oil pressure. The mechanical movement in the gauge has a silicon grease on it that dampens the needle movement. As the grease dissipates or wears out the needle starts to jump around more making it look like something has changed with the oil pressure.

 

[Toothcarpenter]

Thanks Vicki; I have stared at that flow diagram. I will tear into it tomorrow, and have something good or sad to say soon. It makes lots of pressure, with hot 20/50, and straight 50wt. so I will start out by inspecting the relief valve, and then running it again. I hope that is the area of concern. Cub Builder speaks of his experiance with the wrong ball in the relief valve. I am real tempted to procure the correct part number for sure, and put a new one in as well as the spring. It looks like some research is in order, as possibly different spring rates are available. ed

 

[Toothcarpenter]

I read that converting to the "new style" valve involves pulling the sleeve portion of the non adjustable valve, from the case, with a tap, threaded into it, I think 4 threads, or turns. sounds kinda hookey to me. Anyone done that maneuver before, and willing to comment?

 

[Steve Pierce]

It gets done at crankcase overhaul. I would not bother doing it until then.

Old style

New style.

 

[Toothcarpenter]

Thanks for all the help. I will now, know what I am looking at, when it comes apart.

 

[Laz]

Something fairly simple to try:
My gauge was "vibrating" after reassembling my engine (it hadn't before). I bled the line at the gauge and it cured the problem.
Laz

 

[Toothcarpenter]

Once again; thanks to all who bothered to suggest helpful information. I disassembled the oil pressure relief valve, and really didn't find any identifiable particles in it, but thouroughly cleaned it and the seat area, also at the same time, I brazed the fitting to the oil pressure guage line closed, and drilled a tiny hole thru the plug, so am not sure which act cleared the problem. The way I am plumbed, it is all uphill to the guage, so I think to bleed the line would be a good idea, especially for warmer times when the oil will run a bit hotter. Oil pressure is excellent, and the fluttering guage is calm now, so will bleed that line as Laz suggests, and hope for lots of hours looking down at the landscape. Sometimes I am amazed at how dumb I am. I was intently studying the accessory case, for the pressure releif valve. You would thing I would know where it was, after having assembled the engine a year ago. No deal. The pictures posted, finally got me to climb up on a stool, and look down at the top of the engine inside the baffleing. Ah Ha, there it was. Of course that was after I had all the lower cowling off, and was mentally preparing to swing the engine away on the mount, to make access better. All in all, I am grateful for the help, and wish I could return the favor. Ed

 

[Steve Pierce]

I have a PA12 in the shop with the old 4" Stewart Warner oil temp/pressure gauge. Customer swore the bouncing oil pressure needle was air in the system. i guess after standing on his heading bleeding the line he didn't solve the issue. Talked to Butch at John Wolf & Co. and he said could be one of three things. One being the pivot that the needle rides in, the hair spring has gotten weak that dampening fluid or the mechanism is gone. $40-100 to repair. In the mail to him now. Thought others would find this useful.

 

[Captain Ron]

A couple additional questions for those in the know. I've got a case in the shop with no inner sleeve installed and I can't quite tell if it is the old style and I need to install a sleeve, or it is the new style and is ok as-is.

1. Does anybody have a picture of an engine casing with the old style relief valve sleeve removed?
2. Or a picture of the sleeve alone/uninstalled?
3. What exactly is the machining operation to do the conversion?

Cheers,
Jeff

 

[Cub Builder]

Jeff, the case is the same regardless. It's a matter of which relief valve cap you have. One has a larger bore the sleeve fits into. The other two (adjustable and non-adjustable) have a smaller bore that fits much tighter to the check ball and eliminates the need for the sleeve. The photo below is the cap that requires the sleeve in the block. It's a bigger bore than the other two. I'll try to get a picture of the smaller bore cap tomorrow if nobody posts one before then. pn 76529 is the smaller bore cap that you adjust with washers (usually 4 or 5 is about right), and pn 77808 is the adjustable cap. Either will work fine on your case with no sleeve.

-Cub Builder

 

[Steve Pierce]

My post #18 has the pictures of the two different oil pressure relief valves. They are machined differently in the case.

 

[Captain Ron]

Thank guys. I understand the difference in the caps, so no issue there. I've studied your pics Steve (much appreciated!) but I'm still unsure. The case as it sits now clearly doesn't have a sleeve installed - how can I be sure it doesn't need a sleeve? Or is converting simply a matter of removing the sleeve and using the new style cap? I thought there was some machining involved? Probably over thinking it

Cheers,
Jeff

 

[Captain Ron]

Ah, found my answer in an old overhaul manual and SI1172.


So if the sleeve is removed there is no seat whatsoever for the ball to sit on. Since I can see a bevel seat in my case it is either machined that way from new or has had a replacement seat (p/n 76530) installed, either way no sleeve needed.

Cheers,
Jeff

 

[Steve Pierce]

Ah, found my answer in an old overhaul manual and SI1172.

View attachment 63786
So if the sleeve is removed there is no seat whatsoever for the ball to sit on. Since I can see a bevel seat in my case it is either machined that way from new or has had a replacement seat (p/n 76530) installed, either way no sleeve needed.

Cheers,
Jeff

Correct. Also, the seat has no relevance on adjustable on non-adjustable cap. The old caged style relief valve seat uses a larger diameter oil pressure relief valve housing where the machined seat oil pressure relief valve housing is narrower and can be either fixed or adjustable.

 

[Cub Builder]

Correct. Also, the seat has no relevance on adjustable on non-adjustable cap. The old caged style relief valve seat uses a larger diameter oil pressure relief valve housing where the machined seat oil pressure relief valve housing is narrower and can be either fixed or adjustable.

Picture of two of the three available housings. The one on the right is the big bore that needs to have the cage in the case. The one on the left is an adjustable one, although the non-adjustable one looks just the same from this side. Note that it has the smaller bore to keep the check ball in place without a sleeve. If you use the larger bore unit without the sleeve, your oil pressure will jump all over the map. I saw in flight fluctuations of 45 - 90 psi on the last one I found set up with the wrong housing. I've run across this issue where an engine had the wrong cap installed 2 or 3 times over the years.



-Cub Builder