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Oil on windshield

Titan-Xpert

Active Member
I have a friend with a new RV-8; he has been having small droplets of oil deposited on his windshield. At first we thought the front seal was leaking and we replaced several of them. The droplets continued, then we put dye in the oil and checked for leaks and it looks like the front lower case seam is leaking. So now we are disassembling and resealing the engine.
Over the years we have installed many different kinds of engines on our company test mule RV-8, to test performance. I have experienced a lot of different types and amounts of oil leaks or seeps. They almost always wind up on the belly if they are large enough. But never have I seen oil deposited on the windshield. I was wondering if any body else has seen small oil droplets on their windshields?
 
My front crankshaft seal is spitting out a tiny bit of oil and I plan on putting a new one on soon. I get some oil on the canopy from this. Very tiny micro sized streaks, but mostly on the right side of the windscreen (RV-9A).
 
If you have a constant speed prop, you might check it as well. They often will spit oil droplets.
 
My front crankshaft seal is spitting out a tiny bit of oil and I plan on putting a new one on soon.

I think I have a small leak here too. Whats involved in changing the seal? I built the plane but I dont have any real experience in engine assembly

thanks
 
Yeah, on a Cessna 150, Continental O-200, small droplets of oil on the windscreen. Could not find any oil path on the outside of the engine, but there was oil on the lip of the cowl and the windscreen. We pulled the spinner and the base plate for the spinner and about a cup of oil drained on the floor, so the oil was coming from, basically, the base of the prop with virtually no evidence other than a very thin film on the back side of the prop and the oil on the cowl lip. And of coarse the oil on the windscreen.

Tim
 
I think I have a small leak here too. Whats involved in changing the seal? I built the plane but I dont have any real experience in engine assembly

thanks

Lycoming has a document here.
I bought a new seal at Aircraft Spruce for about $15.
I'm going to have my engine builder help with the installation.
 
I had one of these pesky leaks on my RV-8 as well, an annoying oil mist/small droplets on the windshield, a bit heavier on the right side. I thought it was the front crank seal and replaced it twice to no avail... I tried U/V dye in the oil with a black light but it didn't seem to pinpoint it. Finally I tried the technique of dry spray foot powder; I sprayed some on the upper nose case at the CS prop governor oil line elbow. A-ha! The powder was wet! I put a wrench to the elbow and it was barely tight; methinks the engine assembly shop didn't tighten it and I didn't catch it. I put in a new elbow snugged in tight, that seemed to fix it.
 
Installation Tool

EAA Experimenter has a article on how to make an installation tool (since the Lycoming tool is nearly $1,000!):

http://spirit.eaa.org/experimenter/articles/2012-02_sealtool.asp

1202-tool4.jpg
 
If you have a constant speed prop, you might check it as well. They often will spit oil droplets.

Ditto that. For a short period of time, I was seeing a very small streak of oil on the top of my cowl, starting on the top of the right air inlet. I searched and searched and could not find any oil leak within the engine that could come out that way. I looked at my prop and saw evidence of oil/grease or whatever it was on the back side of the prop and inside the spinner. I took the zerk off which I heard a hissing sound as air was exiting or entering since then, I have not seen this.

My theory is that a bit of grease was coming out of the seals and melting due to the hot cowl.
 
I had one of these pesky leaks on my RV-8 as well, an annoying oil mist/small droplets on the windshield, a bit heavier on the right side. I thought it was the front crank seal and replaced it twice to no avail... I tried U/V dye in the oil with a black light but it didn't seem to pinpoint it. Finally I tried the technique of dry spray foot powder; I sprayed some on the upper nose case at the CS prop governor oil line elbow. A-ha! The powder was wet! I put a wrench to the elbow and it was barely tight; methinks the engine assembly shop didn't tighten it and I didn't catch it. I put in a new elbow snugged in tight, that seemed to fix it.
Been there, done that. Careful twisting down too tight on the pipe elbow. The casing is an aluminum casting after all. I cleaned, "lightly" torqued, and Prosealed mine in. No leak.
 
If I re-read the OP enough it was asking basically how the oil got out to the windscreen. If that is the question, some work that DanH has referenced in his shrinking exit thread referred to air in the lower cowling being drawn through the space at the back of the spinner and discharged externally. Some even recirculates into the inlets. With his higher pressure lower cowl, he even sealed the shaft/cowl with a rubber seal.

This is how it might get out, but many comments here about where it originates.
 
In the initial few hrs of our trip to the canyons, a discoloration streak appeared on the top cowl, from the right inlet, next to the spinner. There was not really enough to wipe off. Just discoloration of the primer on my cowl.

I took the top cowl off. Everything appeared dry as a bone. I've seen prop grease emanations on an Arrow before. My prop is dry as far as I can tell. No streaks.

It grew enough to lightly spatter the passenger side windshield.

Cleaned the cowl and canopy. Next flight got a slight wisp on the canopy. Cleaned it. The total time from start to finish was roughly 4 flight hrs. Been good for the next 20 hrs. The stain on the cowl is still there but it is dry to the touch. The canopy is not getting any spatter that I notice anymore.

Dunno'. I'm still guessing a burp of prop grease because the canopy looked the same as the Arrows did.

BillL,
I wondered about inlet backflow next to the spinner and for some short time thought this was oil coming out my alternator blast tube (I have a slight seep at the front of the oil pan so oil is available) because this tube inlet is pointed at the right spot on the cowl. BUT, the inside of the blow tube feels dry. :confused:

On an Occams razor side note, this 4 hr event was after the plane sat outside overnight in a rain storm from hades. First time. She's a hangar babe. I wonder if the high winds and rain moved some oil or grease inside the cowl to a new place?
 
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I had oil on the passenger side of my -10 for the first few flights. Very light, but reappeared after every flight. Ship has the AntiSplat oil separator with vacuum and there was (and is to date) not a sign of any oil leak. Fingers crossed!

Someone asked how many times I cycled the prop on runup a and the answer was two or three. He recommended just once and the oil went away after a couple more flights. Never saw a clear sign of a leak on the hub.
 
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