Oil on windshield and cowl air inlets

[Dale]

I just returned today from Asheville, North Carolina back to Hollywood, Florida. Had an incredible trip back. At 9000 and 10,000 feet I was seeing up to 219 knots. After I landed and put the plane in the hangar I notice a spritz of oil on the windshield and a spritz of oil at the entrance of the cowl engine inlets near the propeller. No oil on the top of the cowl or underneath the cowl near the air inlets. I don't believe the oil was there for my flight because it wasn't smeared back from the air flow. It just looked like a spritz of oil. No oil on the propeller. Does anyone have any idea what this might be from? I looked around and didn't see any oil anywhere else. If anyone can shed some light on this I would appreciate it.

On a side note, I tried to search a previous thread for this but the search function says it won't search 3 letter words (like oil) and it won't allow a search of 2 words together with an "and" in the search line to look for the 2 words together in the same post. You also can't use the quotes to put the words together because you don't know the structure or format the words were used in the sentence. If anyone knows what I am doing wrong on the search please let me know. Thanks.

[OR75]

when was your propeller overhauled ?

[Dale]

Had the engine and prop overhauled in 2011.

Didn't notice anything unusual on the gauges for the oil pressure or temperatures. Everything was in the green.

[takair]

Search "crankcase seal". You should find a good variety of hits, including what you describe.

[N201MKTurbo]

Do you have an oil quick drain?

[Dale]

No oil quick drain.

[rgpilot]

I had a similal event years ago. Found that several of the crankcase bolts had become slightly loose on the top of the case. Tightend them down and problem solved.

[Danb]

Still check prop seal. Same thing happened to me in my J a few yrs ago

[scottfromiowa]

Still check prop seal. Same thing happened to me in my J a few yrs ago

Don't ya have to pull the prop to check the seal?  Wouldn't this be a little much for one "splotch" of oil?  I agree if a trend.  Is there a way to "check" the prop seal without pulling the prop?  If yes, I paid a lot of money twice replacing two seals for mist over entire windscreen that ended up being a case half separation.  I figured I can post here since all kinds of New drivers posted on vintage flaps forum.  I look forward to replies.

[fantom]

Have you taken the cowl off, Dale?

 

Most likely a bit of seepage from a case bolt.

 

With your prop O/H'ed two years ago, that probably isn't it. Maybe you were just going too fast

 

If you need a hand, let me know.

[Dale]

Haven't removed the cowl yet.  I am going to check for oil when I go up this weekend for a short flight and see if this is a one time occurrence or a continuing problem.  If it continues, then I will begin the in depth search to try and determine where the oil is coming from.  There have been some great suggestions here on Mooneyspace.  I appreciate all the responses from everyone.  They have been very helpful.  I will post again once I determine the problem.  Thanks again.

[Shadrach]

2 things come to mind:

 

1) Crank seal (split seal behind the prop flange) is leaking. Easy fix, I'm not sure if you'll need to pull the prop to install or not. Either way, not a lot in the whole scheme of things.

 

2) Over serviced prop.  Can you verify if it's oil or grease that on the winshield? Is there any leakage evident on the face (back or black side) of the prop?  Is it a Hartzell prop? When was it last serviced by a mechanic?

[KSMooniac]

I had a similal event years ago. Found that several of the crankcase bolts had become slightly loose on the top of the case. Tightend them down and problem solved.

 

I had this experience as well... case bolt in the back was loose (oversight on my part!) and the weeping oil worked all the way forward, out the inlet, and onto the windshield.  Counter-intuitive to say the least...

[Dale]

If definitely appeared to be oil not grease.  I checked the back of the prop and there was no oil on the back of the prop.  It is a Hartzell prop.  I believe it was last serviced within the last year.

[Shadrach]

Then I'm betting crank seal; though any seepage/leakage around the top of the engine could "spill" out of the cowling inlets and onto the windshield.

[takair]

To check the crankcase nose seal you need to get your hand behind the spinner backplate and fly wheel. Easier on vintage Mooney than 201. If it is the seal, you will find lots of oil behind the flywheel and it eventually slings out. Prop does need to come off to change it.

[jetdriven]

Happened to us, the crankshaft seal was leaking. The air pulls it out the front of the cowl behind the spinner and puts it on the windshield. Yep, the air flows backward there.

[mikefox]

We recently had the same experience twice!  First time, several years ago, it was the crankcase nose seal.  Second time, last month, it was the propeller seal (Not grease seals on the blades).  If your prop is in good shape, it should only cost $1200 or so from a reputable prop shop.

 

In each case we monitored for a while, carefully cleaning after every flight.  In my experience if you do this, the A/C will soon tell you where it is coming from.

[bumper]

I had a similal event years ago. Found that several of the crankcase bolts had become slightly loose on the top of the case. Tightend them down and problem solved.

 

I had exactly the same thing on my '87 201. It was one case bolt loose at the lift ring. There was a 4 or 5 inch diameter area that was oil wetted, but all the oil was blown off and then went forward and out the small gap between the spinner back and nose bowl.

 

Clearly there is a significant amount of cooling air that is lost due to the centrifugal action of the spinner back plate and the fact that there is no top front blocking baffle that goes from each inlet across the top of the engine as is used on many more modern designs (Van's RV's etc).

 

A friend of a friend's uncle built such a baffle for his Husky and lowered CHT's by 40 degrees in the climb.

 

bumper

[jetdriven]

I don't think centrifugal force has anything to do with it. To me it's an excess of air rammed into the inlets with no where to go. High pressure seeks low, and behind the spinner is low pressure. Some air moves forward, and it may be far more significant than we think. Modern designs get by with a shockingly small inlet in the cowling. My guess is that cowl inlet area and cowl flap area is optimized for Vx climb and most of the time it's far too much. Long EZ's can cool an O-320 160 HP with 3 SQIN of inlet per side.

[Shadrach]

We recently had the same experience twice!  First time, several years ago, it was the crankcase nose seal.  Second time, last month, it was the propeller seal (Not grease seals on the blades).  If your prop is in good shape, it should only cost $1200 or so from a reputable prop shop.

 

In each case we monitored for a while, carefully cleaning after every flight.  In my experience if you do this, the A/C will soon tell you where it is coming from.

If I'm understanding you correctly you had a prop that was throwing grease because no one bothered to install the seal at the blades?  How long was the prop in service before you sent it back?  I went round and round with an IA on this one year. He insisted we pull one grease zerk from each blade and pump it with grease until we had fresh grease come out of the open zerk. I lost the argument and we did as he suggested. Both prop seals herniated the first time we cycled the prop after servicing.  Luckily, Randy at East Coast propeller had OH the prop 2 years before and agreed to reseal gratis, but with the condition that I tell both of the IAs that I work with why it happened and ask them to please never pump a hub full of grease again. A little dab will do ya...

[Mooneymite]

Here's what my Hartzell book says about adding grease for the 100 hour inspection.  As far as I know, there is no "annual inspection" specified for this prop.:

[Shadrach]

Here's what my Hartzell book says about adding grease for the 100 hour inspection.  As far as I know, there is no "annual inspection specified for this prop.:

 

I agree, but when you have a credentialed person saying "this is the way I've always done it", it's heard to combat that line of thinking.  Randy told me they see a quite a few props with herniated seals from over servicing...so I know that it was not just my guy.

[N601RX]

The trick is to do it very slowly.

[Shadrach]

The trick is to do it very slowly.

 

 

Uh, that advice can be applied to so many situations... What exactly are we talking about?