Prior owner

It is possible that my hoses went over the top in the past and that might explain why they are so long. I was the first person to remove the oil cooler hoses after they were installed during the engine overhaul, and they are in the same position now as when I found them. I’ll have to check my baffling to see if I have those two large holes. [Edit] whoops I meant to say: The remote oil filter housing does change things- both filter hoses screw into the vernatherm/temp probe housing..but it doesn’t affect the oil cooler hoses.

I think these hoses were ordered up with a fairly bad guess as to length and fitting arrangements... I’m thinking that the installer wanted to make sure that the left magneto would be accessible and removable without disconnecting the oil hoses (which it is). It sure would be helpful to see other M20C hose installations.

Yes, I’ve got the same hoses. The 4.62 inside bend RADIUS would give me a hose wrapped around a 9.24 Diameter.....which I do not have. I Would like to see how others have routed their oil cooler hoses!

Yes, I checked it with a handheld thermocouple unit in boiling water last year when I had it out to make a new pigtail with new pins. The factory cluster gauge was within a couple of degrees of the thermocouple. Also swapped another cluster gauge in, and it was reading the same. I’m going to take another look at all the other oil hoses next week as well.

I’ve got an oil pressure pot to use for testing ( pic below is when I used it after re-installing he oil lines and cooler last year for inspection). The aircraft has older Teflon Lined hoses that were removed for inspection last year. My thoughts are that one of them may have a slight kink where it bends between the engine and firewall, that occurred after re-installation of the hoses. Teflon lined hoses can get a “set” in them and moving them around can be a bad idea. Impossible to see a slight kink from the outside, especially with fire sleeves on the hoses. The hoses are 12 years old but only have 180 hours on them. I elected to keep them after inspecting them, as they appeared to be airworthy, even after carefully running a borescope through each one. I’m going to just replace them. The pic below shows them in the plane after I made some notes on them, prior to removing them for inspection. The hose bend radius behind the engine is fine for the size hose that it is, but I think there is more going on in that bend than I can see just by looking at the outside of it. The photo has a bit of an optical illusion, because it actually looks like the hose is kinked on the outside, but that’s because part of the hose is sitting behind a bundle of wires. Wish I had a better pic of the hose bend, but it actually looks fine on the outside...

I Installed the new vernatherm, and sealed around the oil cooler at the cowling with a nice custom silicone gasket. See pic No real difference in oil temps. I chose not to do anything to the tapered Vernatherm orifice in the accessory case, as it looked fine to me. Test flight showed only a very slight improvement In oil temp, if any. The old vernatherm shows excessive and recent wear on the shaft where the poppet has been repeatedly compressed to its stop (Galling and polished there). See pic. This may indicate that there is a restriction in the oil cooler circuit that is causing the vernatherm poppet to compress the spring and partially bypass the oil cooler. Oil temperature 10 minutes after leveling off at 5500 ft with 82F OAT was around 205-210F. See pic. Oil temp during 115 KIAS climb was between 220-225F. After taxi back hangar, oil temp gauge indicated 200F. Lasar thermometer indicated that oil temp probe housing was also 200F. Front face of oil cooler indicated 177F at the hottest spot. So, oil is getting to the cooler, but I can’t be sure how much... I think I have a restriction, possibly a kinked hose. More exploration coming later this week. Oil cooler is an Aero Classics cooler with correct part number for the M20C, and the manufacture date aligns with the engine overhaul about180 hrs ago. Rather than send the cooler out for service, I’m going to remove the hoses and take a close look at them.

I took my old vernatherm and made a tool out of it to lightly dress the seat in the accessory case. I expanded the vernatherm with a heat gun, then placed 4 number 8 lock nuts under it To keep it from retracting all the way, then pro-sealed everything. The pressure on the nuts keeps the assembly extended and also provides enough friction so that the whole assembly rotates together. If I elect to use it, I’ll use valve lapping compound very sparingly and will of course have to be extremely careful and very thorough with the clean-up. Dressing the seat is accomplished by Twisting the vernatherm by hand back a forth using its threads as a bearing surface. One pic is of the seat in the accessory case.

THAT would make me very happy!

It would have been an even more interesting science project if I had measured everything, but I just don’t have the time right now. I will check the vernatherm site though ( I searched for info on the valve for quite a while and came up with only Lycoming SB’s and a Service Letter. Lycoming has all the drawings for them as well... they were quite helpful. Researching it got me thinking about the pressure relief feature of the valve, and how you would never get an indication On the oil pressure gauge if the vernatherm had to open due to an oil cooler clogging, or due to the valve having weak spring seat pressure... you’d only see higher oil temps as a result. The vernatherm could be modulating all day due to pressure, and the oil press gauge would just remain stable.

$340 + tax, shipping

Small update: New Vernatherm arrived. I tested it against the old one...here are the numbers using my candy thermometer- Expansion from room temp to 150 deg F. Expansion from 150 - 185 degrees F Old Vernatherm: 0.007“ 0.140” New Vernatherm: 0.046”. 0.250” At the 150-185F expansion, the difference between them is 0.110”, which is Approximately the thickness of two dimes. I cannot accurately measure for comparison the length of the each valve from the gasket surface end to the tip of the valve that seats against the engine oil pressure orifice, as the new valve has a different taper ( I couldn’t tell exactly where the valve seats on the taper against the engine without coating it with blue dye and screwing it in- I’m not at the hangar). So, not very scientific or precise here, but interesting to note that the new valve does move sooner, and does move farther than the old valve. I would like to know the exact distance between the gasket surface of the engine and the oil galley orifice where the valve seats, and I would like to know the length of each valve from the gasket surface to the area of the taper where it seats. Then I’d like to know the seating pressure at various temps- that would give me some real data.... but I’m way too busy and short on time to work on that- I just want to go fly! (The new vernatherm is the one on the left - the more silver one with the pinched nut) One other thing- the old valve tip feels ratchety when pushing the spring down. The new valve tip moves very smoothly against the spring Hopefully it will go in Saturday, and we’ll see if it amounts to a hill of beans.

Go fly a 180 horse piper and then fly the G- who’s the dog now?

I was going to reseal my oil cooler at the cowl, but now I am really curious as to whether a slightly tired vernatherm will make any difference at all....so, As much as I dislike removing and replacing the cowls on my plane, I am going to do this: I will only change out the vernatherm for a new one. I’ll leave everything else untouched. Then I’m going to go fly the plane on a 90+F day and report back. Hopefully I’ll get the new vernatherm by Friday. A member suggested that I test it before I install it, as a comparison. So I’ll do that as well ( uncalibrated meat thermometer- the same thermometer that I used to test the old vernatherm). I also think we should take a poll regarding how many of us running warmer oil temps also have chrome cylinders. I have read that this can contribute to higher oil temps due to increased blow-by.

Maybe the top of the green range exists for summertime flying? I very much doubt the heat exchange system in the older models that have cowl-mounted coolers are efficient enough to provide the same oil temperature at 50F OAT as when cruising at 90F OAT.... Perhaps the factory expected temps to run that high when the weather gets hot...?

Check the longeron stiffeners that run underneath the floor on each side of the rear seat... Intergranular corrosion seems to love this spots too.... hard to see them- will need a mirror

Thanks for the tips! Well, the vernatherm failed the test- Lycoming said That it must extend a MINIMUM of 0.160“ from 150F to 185F. It was .020 short by 185F. Doesn’t seem like a big difference, but I guess I’m going to find out when I replace it! Besides the expanding wax Plug getting tired, the pressure relief spring gets tired as well... so no telling just how unhealthy it is, or what the spring seat pressure is at 185F, or even 200F for that matter. A New one has been ordered. In the meantime I’ll rework The oil cooler / cowling sealing To get minimal air leakage there. Will report back after new vernatherm is installed. I don’t have high expectations, but hope to see some improvement. if you’re getting 200 F oil temp in cruise with These hot summer temps, I think you’re probably doing pretty well- the E and F have the “HE” high efficiency coolers- wish we C and D owners could (legally) upgrade to something better.

Prior owner said that oil cooler was flushed at engine overhaul...but there is no record of it, so that will be next on the list. Might just buy a new Aero Classics cooler Instead. Lycoming also recommends that the vernatherm be replaced at engine overhaul, as the wax expanding plug will only function properly for so many cycles. I also want to note that my California winter/spring oil temps run about 5-10 degrees cooler when using 20w50. I switched back to 100w at the last oil change as the hot weather was right around the corner....But even if multi viscosity helps move more oil through the cooler, I think it’s still a crutch- 100w should work fine if everything else is working right. Vernatherm testing tonight!

Lycoming tech support just confirmed that the part number I removed is the same spec as the part number that is specified for my engine. He pulled the drawing for part number 69451(the one I removed) and it's supposed to extend .16 inches at 180F. I've got to run a function test on mine now... Is it's okay, then the oil cooler goes out for service.

Yes, it means that it is fully extended at 185F. I have searched online and cannot find Temp specs for different vernatherms. I do know that there are different styles, and that the older ones can lose the tip nut (it ends up flowing away with the oil to somewhere undesired). It appears that my part number Vernatherm was not specified for the Lycoming O-360 A engines. Some of the Lycoming vernatherms are stamped ‘77C or 173F. Aircraft Spruce drop ships these , presumably from Lycoming- I will have to call Spruce to see what is marked on the newest revision vernatherm that I have ordered. You may very well be correct. If the new one is also marked 85C, I may not see any difference in temps, provided the one I presently have is the same length dimension as the one I ordered.... This leads me to another question: if the new vernatherm opens at the same temp as the old one, and there are vernatherms that open at a lower temp, wouldn’t installing the lower temp vernatherm bring our oil temps down? At least the system wouldn’t be playing catch up after every climb.... if anyone has the later vernatherm, do you know what he temp marking is? Does anyone know whether the vernatherms are manufactured in varying lengths? So Yes, my saga may continue beyond the vernatherm...

Thought I’d throw this into the thread- This is the first summer that I’ve flown my Mooney, and while the oil temp has always run on the warm side (200F oil Temp in winter), when it’s 95+F OAT, my oil temp has been hovering around 220-225F during cruise and climb. Gauge checked with portable thermocouple and is very accurate... I found this today- the wrong vernatherm is installed. It is stamped 85C. Not sure how I missed this, but I did.... I have no idea who installed it. I have ordered Lycoming Vernatherm part # 53E22144 and will post the results of a flight test here afterwards. Hopefully that will solve the High temp problem.

I think the reason is because nobody really wants to stand that close behind A running prop to watch the rocker arms moving...

I don’t see a misfire/detonation event causing pushrod bending... Unless it was prolonged and led to overheating of the valves. Do you have any more data (engine monitor)? On a side note, I witnessed a magneto failure that caused a complete loss of engine power. Some of the internal timing gear teeth broke, the timing severely jumped, causing the affected mag to fire the plugs at a position that was so far advanced that it ignited the mixture while the exhaust valves were still open. It backfired and shook horribly, produced almost no power but continued to run. My faith in the dual magneto concept was shaken that day...

I’ve got all the adel clamps on my 64 D, but have never seen that curved heat shield piece....anybody have a pic one installed?

Here’s an obscure bit of info: There is a ball bearing test that can be conducted on flexible lines...I believe 43.13 specifies the correct diameter ball bearing to use for each size hose. I have yet to meet an A&P who has a set of ball bearings for this purpose though... you drop the ball bearing in the hose, and if it makes it to the other end, then the inner diameter is within min spec.

I see big black squares....!