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oil filler tube leaks

Mike Ice

Well Known Member
Hello,

There is a leak at the base of the oil filler tube on my new engine. Is this common? I will attempt to tighten it today. I was just wondering if anyone else has experienced this problem and what is/was the fix?

Another RV-9 took to the air last Sunday. This one is in Alaska. I flew 8 hours yesterday and am still trying to figure out how to land gracefully. Most of the landings so far have been more arrivals but this little airplane flies great.

Mike Ice
Flying RV-9
9 hours
 
Pretty common leak, especially after a long storage period. The gasket under the tube shrinks a little bit over time, requiring the tube to be re-tightened and re-safety wired
Good Luck,
Mahlon
"The opinions and information provided in this and all of my posts are hopefully helpful to you. Please use the information provided responsibly and at your own risk."
 
Mike,

Good to hear another -9 is flying.

Keep working on those landings, they will come. Because of the wing, both three point and wheel landings take precise speed control to master. By the end of your 40 hours, you will wonder what the big deal was. Besides, with that BIG VS and rudder, it is very easy to keep straight.
 
leak

Remove the tube and gasket. Clean the mating surfaces and the gasket. Apply a coating of fuel lube to the gasket. Re-install the tube by hand. My tube is plastic so I lightly snugged it with a wrench just to verify it was seated against the engine case. Safety wire and go.

Still dry after 75 hours,
Steve
 
Common problem since the tube is a builder installed part on most engines (they are delivered without the tube installed making it easier to get the engine on the mount, etc.)

One operational cause is over tightening the dip stick. It does not need to be cranked on tight. Just lightly snug will keep it on. If you over tighten, it puts a lot of torque on the tube when removing it. This breaks the seal and you then have a leak.

What I do...
Start with a very clean dipstick tube, engine case, and gasket (you can reuse the old gasket if you can get it cleaned up real well).
Put a super thin coating of high temp RTV on both sides of the gasket (this should be just enough to wet the surface, you don't want a big blob of RTV squeezing out inside your engine).
Install the tube and gasket.
Use a big wrench on the nut portion of the tube to get it snugged up tight. It needs to be good and tight but remember it is made of plastic.
Now for the most important part...Use .041" safety wire to safety the tube. It is very important that you get the safety wire pulled very tight. This is to prevent the tube from being able to rotate even the minutest amount. If the tube ever rotates at all you have another leak because the seal has been broken. If your first try with the wire isn't tight, take it off and try again until the wire is stretched good and tight
Now condition yourself to not over tighten the dipstick (ever notice that it gets even tighter and harder to remove after the engine is hot).

This will usually provide a leak free dipstick tube for a long time.
 
leaky tube

Many thanks for the great tips. I will try them all or at least one at a time today when I change the oil.

Mike Ice
18.7 hours and still smiling, actually the smile is getting larger.
 
Oil Filler Tube Leak

If you put REAL gaskets (the orange ones) on your Rocker Box Covers, they come with a Dip Stick orange gasket also. Put that on, hand torque, safety wire and there will be no further problems.
 
What Stu Said...
Had same problem, thats how I fixed it... "Real Gaskets"
DM



If you put REAL gaskets (the orange ones) on your Rocker Box Covers, they come with a Dip Stick orange gasket also. Put that on, hand torque, safety wire and there will be no further problems.
 
Still have a leak

Folks,

I removed the oil tube filler yesterday and found a robber O ring on it. I replaced the O ring with a regular Lycoming gasket and thought that had to be the problem. But no joy. Well that O ring was probably leaking as well because it was "sqiushed" out from being over tightened.

Now I am beginning to think the fitting just above it that has the oil line that goes to the pressure sending unit might be the culprit.

Does anyone have any experience dealing with a leak in this area? Was it the line or the fitting? How did you fix the problem?

It looks like if I have to remove that fitting I will have to remove the engine mount. Does that seem right? Any tips on this will sure be helpful.

Mike Ice

a little over 20 hours and enjoying the process but I will enjoy it a lot more when I can stop this pesky leak.
 
oil leak found

Finally found the source of the oil leak. I hope.

The high pressure oil bypass gizmo, not the correct term but I can't remember the name, which is located right above the oil filler tube just to the rear of the #3 cylinder was the problem.

The fitting has a spring and a ball bearing in it which can be adjusted to regulate oil pressure in the motor. The fitting had a small crack around the threads and I could not see it until this last time I took it out and replaced the crush gasket under it. Each time I took it out to examine it and replace it the crack got larger when retightening so the leak got worse but finally the crack was also large enough to see.

The oil leaked down from that part and got into the airflow and was then spread around which made it difficult to pin point the source of the leak.

As soon as I can get another part I will install it and hopefully the leak will be history.

Mike Ice
 
If you put REAL gaskets (the orange ones) on your Rocker Box Covers, they come with a Dip Stick orange gasket also. Put that on, hand torque, safety wire and there will be no further problems.
Does anyone know where I can get a "good" gasket for my 0-320 dipstick tube and what size I need (are they standard sized?). I've been chasing weeping oil and the oil dipstick tube is one potential culprit. I'm doing my condition inspection this month and want to have the right gasket on hand when I change the oil.
Thanks.
 
Does anyone know where I can get a "good" gasket for my 0-320 dipstick tube and what size I need (are they standard sized?). I've been chasing weeping oil and the oil dipstick tube is one potential culprit. I'm doing my condition inspection this month and want to have the right gasket on hand when I change the oil.
Thanks.

Direct from Real Gasket company website for $3.00

http://www.realgaskets.com/files/horizontal.htm#lycoming

Part# RG-72059

rg-72059.jpg


I've got a plain o-ring on mine and it doesn't leak. That's a cheap alternative too.
 
Oil Pressure Relief Valve

Mike,
I just fixed that problem on my -4 last week after chasing the leak for 3 years. My oil pressure relief valve was leaking from around the adjusting stem. You could barely see the oil trail it left on the baffles but it showed up real well near the dipstick tube and #3 drain back line and on the accessory case. I ordered a replacement with gaskets from A.E.R.O who advertise with VAF. Real good company to work with. Had it within 3 days of placing the order and they were cheaper than most others I found. Be aware that the internal ball and spring are not included, so keep them for reuse.

Alan
 
Picking up on this old thread:

Aircraft Spruce now sells the oil filler gasket too. Shipping is cheaper than from Real Gaskets.

Part# 08-13621
MFR Model# RG-72059

David
 
The pipeline patrol company I work for uses the Real base gaskets and their O-ring for the cap. We hand tighten them and safety wire them both directions so over-tightening the cap won't cause the tube to squash the gasket. Also, the gasket must be installed clean and dry, otherwise it will extrude out with even moderate torque. We have thousands of hours on these with no leaks.
 
We hand tighten them and safety wire them both directions so over-tightening the cap won't cause the tube to squash the gasket.

Excellent point. I always safety wire oil filler tubes both directions, loosing and tightening direction. I also use the orange REAL gaskets instead of the stock Lycoming gasket.
 
What torque do you use on the filler tube? I have a Superior XP-IO360 engine, and can't seem to find the torque in the maintenance manual.

Is a special crow's foot required to apply the torque? Or do you just hand tighten as far as you can, and safety wire both ways?

David
 
300 inch lbs must be the torque for the stock Lycoming flat gasket. Much lower for the REAL brand thick silicon gasket. I tighten the silicon version until I just detect migration and call it good. You don't want to squash it out and away from the mating surfaces.

Here is a photo of my RV-3 dipstick tube where I added an extension, so I used two of the REAL gaskets.

2iIvT2B.jpg


I took that photo 5 minutes ago as part of this post. Looks like the bottom one might be a bit too tight but I will monitor it. Se how it has started to migrate out radially? I squarshed it a little. I used DC4 compound to lubricate the silicon gasket and this could be contributing to the migration. Also, note the safety tying in both directions, tighten and loosen. I used safety cable on the bottom due to access. And that lava looking glop at the bottom on the crankcase boss is left over Permatex from the previous owner. He slathered it on everything. I cleaned it off the mating surfaces with Tolulene prior to re-installing the dipstick tube. As a rule my work is airworthy if ugly.
 
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Looks like the REAL gasket is thick.... Just use a normal "O" ring...pennies at your local ACE hardware store.
 
300 inch lbs must be the torque for the stock Lycoming flat gasket. Much lower for the REAL brand thick silicon gasket. I tighten the silicon version until I just detect migration and call it good. You don't want to squash it out and away from the mating surfaces.

Here is a photo of my RV-3 dipstick tube where I added an extension, so I used two of the REAL gaskets.

2iIvT2B.jpg


I took that photo 5 minutes ago as part of this post. Looks like the bottom one might be a bit too tight but I will monitor it. Se how it has started to migrate out radially? I squarshed it a little. I used DC4 compound to lubricate the silicon gasket and this could be contributing to the migration. Also, note the safety tying in both directions, tighten and loosen. I used safety cable on the bottom due to access. And that lava looking glop at the bottom on the crankcase boss is left over Permatex from the previous owner. He slathered it on everything. I cleaned it off the mating surfaces with Tolulene prior to re-installing the dipstick tube. As a rule my work is airworthy if ugly.

What's your reasoning for lock-wire in both directions?
 
It keeps the oil filler tube from loosening when a dipstick tightens the dipstick.

So here's what happens. On a en-route stop on a cross country or after parking the airplane for the day somebody checks the oil. The engine and components are hot. As any experienced Lycoming owner knows the dipstick is only to be tightened slightly and not hard tight. Such as using the knuckles between the index and middle fingers rather than honkering down with a whole hand full of fingers. Probably something like a 1/8 turn after the dipstick o-ring touches the filler tube.

So after checking the dipstick the let's say someone like Cousin Everett tightens the dipstick down good and tight. Cousin Everett works on Caterpillar tractors for a living and wants to be sure to tighten the dipstick good enough that the dang engine oil stays in the engine, especially since the next leg is over the mountains or the lake. This type of mistake is common at flight schools and other times when a person not too confident in the flying contraption gets his hands on the dipstick. If there is one thing they can control it's the tightness of the dipstick. Since the engine and oil filler tubes are hot the tube base gasket gets compressed by the over-tightening action, even the Lycoming flat gasket. Much less the silicon or o-ring type gaskets. Those don't stand a chance. In the over-tightening process having only a single safety wire for the loosing direction allows clockwise rotation of the tube and the safety wire gets some slack due to the rotation and gasket compression. When the engine cools down overnight the pilot plays heck getting the dipstick loose on pre-flight because as it cooled overnight the threads shrunk and made things even tighter than Cousin Everett could have imagined. So the pilot has to really twist hard to get the dipstick out of the tube. When the cap breaks loose so does the compressed gasket at the base of the tube, at least until the slack is out of the safety wire. Now the tube has become loose due to the compressed base gasket.

From that point on everybody checking the oil notices there is a slight amount of turning slack in the dipstick every time they check the oil. They blame it on the gasket or the guy who had to break the filler cap loose. But the real problem was Cousin Everett over-tightening the assembly a few flights back. They squawk the filler tube so a mechanic can change out the gasket and tighten her down real good. If he re-safeties with only one wire in the tightening direction the cycle will continue. He now has job security and stocks oil tube gaskets.

So to avoid such nonsense the second safety wire in the tightening direction keeps Cousin Everett in check by not allowing him to compress the gasket at the base of the filler tube with the engine hot. His over-zealous torquing of the dipstick is reacted by the second safety wire in the tightening direction. And it keeps the next guy from getting accused of loosening the filler tube trying to undo what Cousin Everett done.

Basically you don't want the filler tube(s) to rotate either direction. You just want it solidly locked no matter what type of twisting might come it's way.

Jim
 
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A properly installed tube will only need one safety wire in the tighten direction. And it has been done that way for over 70 years.

You must do what makes you feel good.
 
A properly installed tube will only need one safety wire in the tighten direction. And it has been done that way for over 70 years.

You must do what makes you feel good.

No matter the gasket material? No matter the oil tube material? 70 years ago the tubes were aluminum. Now the tubes are plastic. My IA has been one for 41 years specializing in small GA aircraft. He stocks oil tube gaskets and says everyone will need one sooner or later.

See post numbers 2, 5 and 16 in this thread above. Adding this post to a search for all threads on VAF on this subject combined with your statement would yield the conclusion that not many people know how to successfully install a oil tube base gasket to last to TBO. Here's a thread that's pretty enlightening: http://www.vansairforce.com/community/showpost.php?p=1267600&postcount=14

A full internet search will find this same chronic issue from many Lycoming operators in dozens of experimental and type user groups. The Mooney guys really carry on about this. Not a lot of feel good results.

I am not saying the two direction safetieng is the best or only way to do it. There has to be a better way. The more I learn the more I realize how much I have left to learn. So with all respect and seriousness, what is the proper way to install an oil tube base gasket to last the life of a 4-cylinder Lycoming after 70 years of in the field experience? It would be a feather in my cap to share that with my IA, who is open to any and all ideas and also learns something new every day.
 
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