Engine Oil Leak

[M20JFlyer]

Need help and suggestions for best method to locate an oi leak.

Has anyone had experience or succes using an OIL DYE or talcum powder approach to loacating leak?

I will make a short list of what has been done, this is not a wet/messy inside the cowl leak..do dripping but I have a stream of oil from cowl back over wing only on left side of fuselage.

Most obvious checks: Mag secure NO VIS..valve cover 4 new cork nv  4 oil return lines new hoses new clampps NV  oil sump drain hose and new hose clamp..check accesory case vac pump,fuel pump, governor assembly oil filter assemb.,,NV  not sure of terminoligy but slot on sump drain line is correct large O rings on return air tubes to sump replaced.

Prop assbly nv .. oil drain new O ring check assby. oil sump area visual noV replaced the push tube gaskets on left side spent time checking case joint. Am sure their is some obvious place or situation we have overlooked. The inside of left cowl and left side of engine have light film but no obvious leak location is evident.

Comp is 70+ all four..CYL temps, EGT's , oil temp and MP are normal. Use areoshell 100w-plus running six qts. Oil consump is just under one qt in 4.5  hour. Run WOT X 2500  20 degrees LOP. Any suggestions or a name of an overhaul shop or good source to find a small pesky leak will be appreciated. Based Houston    N9135 W   

Pat Lyons

[FAST FLIGHT OPTIONS LLC]

Ahhh...the old oil leak on the left side of the cowling.  I remember when I purchased my first Mooney (M20J) and I too thought I had an oil leak as I was cleaning off oil from that area after every flight   It was always more pronounced with extended high power climbs.  I actually started a thread about it on this site.  I had a mechanic I trust very much once tell me oil on planes is like sap on trees, you cant have one without the other.  Some of my first question to you would be why do you think something is leaking? Do you have an air/oil seperator? How much oil do you fly with?  In my J anything over 4.5 would blow out.  Im my K I keep it at about 6 or I will have the same problem.   

[jlunseth]

This is simple.  Ever put oil in your engine?  Ever maybe spill a drop or two inside the cowling?  Maybe right when you tip th oil can into the filler neck, or a little drips off when you remove the can?  What happens next is called a "chafe leak."  Some of that oil finds its way to the seam between the cowling and the fuselage, where it picks up a small amount of metal and then spreads back over the wing because of the very high pressure from the airstream around the aircraft in flight.  Sometimes chafe leaks can extend back most of the length of the aircraft. It does not take any significant quantity of oil to cause this, it is rather the airstream pressure that causes a tiny amount to go a long way.  The streaks are black, or kind of dark grey, and very obvious on a white paint job, so the first time you see one you worry do I have a leak?  I sure did.  Chafe leaks are just nothing, they are not a leak, they are a drip gone viral.

However, having had a true leak, I will be the first to tell you that you should have all leaks checked out by your A & P.  So take the plane there and ask if it is a leak you should be concerned about.

If you are not losing oil on the dipstick after many flights, you have a chafe leak, and a rag plus a little Aviation Simple Green will take care of it.   

[bnicolette]

Hi all,

A couple weeks ago I used some mineral spirits to totally clean off my engine in an effort to finally find some small annoying oil leaks.  After about 8 hours of flying I pulled the cowling and had my mechanic come over for a looksie.  There was nothing of great concern, but I wanted to try and tackle a couple of them that we think we found.  There was a bit of oil on the bottom of #1 & #2 intake pipes and my mechanic thought that maybe we should replace the gasket on the intake.  I'm not sure why there would be oil coming out of there and he said that perhaps the valve guides we a bit worn and that could be the culprit.  Nothing nearly bad enough to warrant pulling a cylinder but we checked the compressions just to be sure.  #1 was 76 and #2 was 77.  The next little leak that we tried to correct was the crankcase seam from the front of the engine back to where the oil pan? is.  We just used some fuel tank sealant and put it along the seam to see if that would help.

What are your thoughts on the oil on the bottom of the intake pipes?  Do you all see any oil there on your engines?  If it's not coming from the intake where else could it be coming from?  I suppose with all the air moving around in the cowling, it could just about be coming from anywhere?  Thoughts?

The good news is that after 8 hours of flying everything on the back of the engine, firewall, etc was bone dry and looks great.

[jetdriven]

I see that oil on the bottom if the intake pipes too. I am not sure where it comes from. We are dealing with a recurring leak in the front crank seal. RV guys use permatex black silicone and then put proseal over the edge of the seal.  Maybe that is the next idea.

Also, one thing, if you have a dual mag, and you notice a fresh oil leak, check the mag mounting nuts before further flight. Thats the first symptom of a loose mag, a leak at the base gasket. Ours is starting to leak there, but it is because we moved the mag for a timing chage. I put torque seal on both of the mounting nuts.

 

[jetdriven]

Quote: M20JFlyer

Need help and suggestions for best method to locate an oi leak.

Has anyone had experience or succes using an OIL DYE or talcum powder approach to loacating leak?

I will make a short list of what has been done, this is not a wet/messy inside the cowl leak..do dripping but I have a stream of oil from cowl back over wing only on left side of fuselage.

Most obvious checks: Mag secure NO VIS..valve cover 4 new cork nv  4 oil return lines new hoses new clampps NV  oil sump drain hose and new hose clamp..check accesory case vac pump,fuel pump, governor assembly oil filter assemb.,,NV  not sure of terminoligy but slot on sump drain line is correct large O rings on return air tubes to sump replaced.

Prop assbly nv .. oil drain new O ring check assby. oil sump area visual noV replaced the push tube gaskets on left side spent time checking case joint. Am sure their is some obvious place or situation we have overlooked. The inside of left cowl and left side of engine have light film but no obvious leak location is evident.

Comp is 70+ all four..CYL temps, EGT's , oil temp and MP are normal. Use areoshell 100w-plus running six qts. Oil consump is just under one qt in 4.5  hour. Run WOT X 2500  20 degrees LOP. Any suggestions or a name of an overhaul shop or good source to find a small pesky leak will be appreciated. Based Houston    N9135 W   

Pat Lyons

[Skywarrior]

Had a front crankcase seal leak soon after I bought my plane; it displayed a spray of oil around the front opening of the cowl. Kinda looked like a snot-nosed kid...

[carusoam]

Bret,

O360... the oil return lines from the rocker boxes are plumbed near the air intake.  They get old and are kept in place with clamps.

Check the tightness of the clamps or replace the old ones.  Check for oil on the oil lines.

This was something I found on my C.  Easy low cost fix...

The lines are gravity fed so there is no pressure, the leak is very low, a drip every now and then.

After that have a mechanic remove the intake pipe, it should be clean. On carbureted engines, it will be full of dark blue goo....

If the valves are worn, and oil is leaking, you might see it show up on the spark plug.

My experience is from the carbureted version, yours may be different...

Best regards,

-a-

[MooneyMitch]

Mentioned in all the responses above are typical oil leak areas on the Lycoming IO-360's with my experiences.

Upper intake tube gaskets and/or lower intake tube O ring type seals, crankcase half seal [check for proper torque of these fasteners], prop and front crankcase seals, gaskets around magnetos, and other rear engine accessories.

With regards to the upper intake tube gasket areas, the actual intake tube securing flange can wear inside, creating a loose tube.  This is identified by trying to wiggle the intake tube near the base of the cylinder.  If the bolts are tight and you've got a good gasket installed, then the flange has worn and no amount of tightening or gasket installation is going to cure the problem.

As mentioned, the cylinder oil return lines back into the crankcase.  Make sure the lines are secure at the cylinder and at the lower clamps as well.  Not only could the clamps be loose, but the rubber sleeves may be cracked or broken. 

Oh yes, don't forget to replace your cork valve cover gaskets with the orange looking high temperature silicone gaskets.  That's a good place for oil to sneak out too!

Keep after it and you'll eventully get a clean engine again.  

 

[Piloto]

I has been annoyed by oil leaks too. I found some ways of identfying them that may help.

There are essentially three type leak sources:

Engine off leaks. These are the ones that you see on the hangar floor next day after cleaning. They mostly come from the oil sump or bottom side of the cranck case. And of course they leak also with the engine running. To find them clean the engine of any oil first. Top off the oil to the max capacity plus 1qt. Allow the plane to sit for two days or more to show a leak. Look on the bottom side of the engine around the sump, case split gasket , drain valve and plugs. You may be surprised where an oil leak may show. During this test I found that mine was leaking thru a pin hole in the case. The engine case is a casting with some areas of coarse grain. If one of these grains fall off it will cause a leak. I plugged mine with Marine Tex and problem solved 1,500 hrs ago with no recurrence.

Engine running leaks. These are the hardest one to spot. Since you already ruled out bottom side leaks with the above test these are the ones that show around the engine oil circulation path. Again clean the engine of any oil. Top off  the oil to max capacity plus 1qt. With the cowling off run the engine on the ground at low RPM to avoid blowing the leak oil from its source. Run it for about 10 minutes and one minute with the prop control fully out at 1500 rpm. After the run look for leaks around return lines/hoses, valve covers, cylinder base, push rods shrouds, magnetos, prop governor/lines, fuel pump, turbo lines, crankshaft seal and case split. I found that most common leaks are on the valve covers, specially with cork gaskets. Change these to the orange rubber gaskets and they will last 2000hrs leak free. The oil return hoses are also prone to leak. Retighten the clamps, if not replace the little hose. Push rod shroud seals are also prone to leak even with new O rings. I found that the best way for this is just to apply a good engine sealant around it. In mine it lasted longer than new O rings all the way to overhaul time. Engines accessories (mags, pumps, prop gov.) gaskets are also prone to leak.

Oil breather leaks. During engine combustion some of the high pressure gases leak thru the cylinder rings into the cranckcase. This causes a high pressure in the case that is relieved thru the cranckcase breather port on top of the engine. When this gases escape they carry oil in a semi vapor state. They are discharged thru the breather line that exit at the cowl flap doors. The oil will normally show on the belly of the plane and on the gear door. To reduce the stains and save some oil an oil separator is the best way to go. I installed on mine the M20 with excellent results. But you have to install it properly to be effective. The separator inlet has to be above the breather port. There should be no holes or openings on the breather discharge line except for the opening at the end of the line. The oil return line on mine is to the bottom side of the rear valve cover. The M20 separator is factory standard on the later Mooneys.

Hope the above helps you. 

Keep it clean

José

 

 

 

 

 

 

[bnicolette]

Hey guys thank you for the above information.  All good stuff.  I do have an M20 seperator installed on mine.  I don't get any oil on the belly and even after the 8 hours of flight after cleaning the engine and belly, the belly is extremely clean.  All I get is some exhaust "dust" for lack of a better word.  Very easy to clean off and absolutely no oily residue.  I also get some drops out of the breather that I notice on the floor (left side beside the nose wheel) next time I come to the hangar.

I did have a leak around the magneto but we had this fixed months ago when we sent the mag out to D.M.'s guy in Texas for a overhaul.  We do have torque seal on the bolts and I look at them everytime I have the cowl off.  We also put torque seal on the intake bolts today so I can keep an eye on those too without needing to put a torque wrench on them.

Thanks for all the suggestions.  I'm on a mission now to see if I can rid myself of some of the little leaks without throwing a bunch of money at them.  None of them are anything that I or my mechanic thinks is a problem it's just the fact that they are there!!  

[Lood]

We,ve used the powder and dye to detect invisible cracks in my crank case as well as to determine the origin of a leak at a through bolt. It worked incredibly well.

[ELT]

I hope your oil leak was not like mine.  Several mechanics and I missed the crack in the case untill the alternator and servo were removed.  Good Luck!

[Lood]

My crack ended up in an extremely expensive, complete firewall forward overhaul...

[superfly1]

It's amazing what someone can learn on the internet.  The last posting in the this thread was May 24th, 2012.  Here it is March 22nd, 2014, nearly 2 years later.  Anyway, flying my Mooney M20C today, I noticed an unusual amount of oil on the left side of the aircraft, coming from the cowling area.  Following a panic attack and sure I could find something fast to fix once I decided to disaasemble the hoods, I pretty much found nothing.  Then I read the below thread and remembered I thought it would be smart, somewhat proactive to fill the oil reservour with well, 7 quarts of oil on the dip stick instead of the 5.5 to 6 max. Guess where the oil went...........?

[carusoam]

Welcome aboard!

-a-

[Piloto]

Pat

 

Since you found no leaks on the engine or on the belly. it is likely the leak is coming from the breather hose/tube. Check for any holes or cracks on the breather line.

 

José 

[Hank]

It's amazing what someone can learn on the internet.  The last posting in the this thread was May 24th, 2012.  Here it is March 22nd, 2014, nearly 2 years later.  Anyway, flying my Mooney M20C today, I noticed an unusual amount of oil on the left side of the aircraft, coming from the cowling area.  Following a panic attack and sure I could find something fast to fix once I decided to disaasemble the hoods, I pretty much found nothing.  Then I read the below thread and remembered I thought it would be smart, somewhat proactive to fill the oil reservour with well, 7 quarts of oil on the dip stick instead of the 5.5 to 6 max. Guess where the oil went...........?

 

My C usually spits any overfill out onto the belly.

 

After one flight home in IMC, there was a wavy gray stripe down the passenger side, starting at the cowl opening and running almost to the trailing edge of the wing. AP diagnosed it as cowling rubbing, put some Teflon tape in a couple of spots, problem has not reappeared. But it was difficult getting the mark all the way out; it lightened easily but was still slightly visible. Irritating, but not a safety or engine issue, thankfully.

 

Here's hoping yours is as easy!

[joepilot]

 

Related to this old thread I found, here's a small leak I have on cyl #2. (The dark on the flange/collar bolt is oil; gasket area wet but hard to see) It's all oil, no fuel. Oil return line is dry, valve cover gasket dry, push rod sleeves above are dry, front of engine seems dry, cylinder assembly above this point seems dry. Could oil be leaking from an intake manifold gasket?? Oil consumption is 1qt per 8.2hrs over the last 30hrs or so. It's small, but annoying regarding belly cleanliness. 

 

I have it all cleaned up and going to fly and try to be a detective, but any ideas where I should be looking?

 

Thanks!

[carusoam]

Ask your mechanic to check the torque on that bolt and it's twin brother...

He may make recommendations based on what he sees.

Private pilot advice. I am not a mechanic...

-a-

[jetdriven]

Check where that blue -AN fitting is threaded into the head. That drains the rocker box and it appears oil is running down the head and dripping off that bolt. Could be coming from the -AN fitting.  Also check the valve cover.

[sleepingsquirrel]

Check where that blue -AN fitting is threaded into the head. That drains the rocker box and it appears oil is running down the head and dripping off that bolt. Could be coming from the -AN fitting.  Also check the valve cover.

I strongly agree it is likely where the AN elbow is threaded into the head. I used Indian Head gasket shellac on those threads  and have a good seal with no leaks.

[Alan Fox]

Common Lycoming leaks are , The gasket on the oil fill tube , rubber lines on the oil returns , pushrod tubes , crankcase seam bolts coming loose...

[jetdriven]

The only repair I've seen work on that oil fill tube is a thin o-ring on the bottom of it. That factory paper gasket arrangement always leaks.

[N601RX]

I've found that prc works well if you clean it good 1st and the safety it down tight.