Crank Seal Leak

Gents, I have discovered a black oil dripping from my crank seal. Has the consistency of ink. My TMX 0360 has 70 hrs since new and I found this during my first RV8 annual. Looks to be a slow drip but I'm not sure what this means. I have an E-mail into Mahlon at Mattituck but would appreciate any thoughts the forum may have on this subject.

Another Thread

http://www.vansairforce.com/community/showthread.php?t=16115&highlight=seal+crank

Doug, your description of "black oil--consistency of ink" raises a bit of a red flag for me.

This sounds like the crud that you get when there is fretting going on between pieces of aluminum. I used to see it a lot when I was in the VW repair business, usually caused by case bolts loose.

Take a bit of the "inky oil" and smear it on a clean piece of white paper, take it out in the sunlite and look at it with a magnifying glass.

What you really dont want to see is any "metallic" look, or glitter like stuff. This would indicate something loose that is rubbing something it shouldn't.

Here is hoping all you see is just plane black oil.

Crank Seal

Me too. Had a local A&p look at it and he just said keep watching it... May even fix itself? I'm not sure if it took 20 hrs or 1 hr too run down to the sump but I will run up the engine today and take a look.

Is your crankcase vent in or outside the cowling? Many builders, myself included, have the vent dump down on the exhaust pipe within the cowling. This eliminates the annoying drips on the floor of the hangar. However what I found, with testing, was that this location actually pressurizes your crankcase, causing a series of little leaks, including around the crank shaft seal. I have routed my vent aft of the cowling outlet and for the last 60 hours I have had NO leaks firewall forward, my oil consumption has decreased, and my aircraft belly is also cleaner.

Tom, could you snap a picture of the vent outlet location that is working for you? Thanks....

ditto

Tom,

Ditto gasman's request...


THX
Ron

I had a leaky crank seal on my engine around 60 hours. I had oil pooling on the inside of the prop hub. It also began to leak onto my alternator & seep up to my intake. Changing the crank seal and sealing with pliobond did the trick. I used the non-split seal.
Forty hours later, no leaks.

Same Experience as Dan

Had an ugly leak. A hangar neighbor said it was easy to replace. He was right. $25 and and hour later, no leak and a clean engine again. I was nervous to try it myself but it was easy and quick to do a good job.

I also have the same experience as Dan at 160 hrs. I called Bart at Aero Sports Power and he told me to change the seal at his cost (within warranty). Now at 267 hrs it has no leak. I keep my vent inside per Van's drawing. I fill oil to only 6 qrts and consume very little (0.05 qrt/hr hobbs).

I do not have a picture of my vent location but each installation would be different. All you have to do is to get the vent outlet aft of the cowling. An elbow on the existing vent line with an extension should do the trick.
I was an early adopter of the vent on the exhaust pipe and I remember thinking that all the certified planes, with their vent lines aft of the cowling, were really old fashioned. Now I know, at least for my installation, that they were right.
How many RVs are sealing and replacing prop seals for nuisance leaks that are caused by venting in the cowling? These fixes will help for a while but constant internal pressure will likely cause the same problem again. I spoke with Bart Lalonde about this issue at AirVenture and he was in aggreement that positive pressure in the crankcase could cause these annoying leaks.

crank seal

Thanks guys. My vent is just aft of the cowl but does not exit below the cowl. Turbulence may be present which pressurizes the vent. I'll try lowering the exit below the cowl. I also added piccolo tubes to my exhaust to reduce floor vibration. This may also lower the air turbulence.

Just to ditto what Tom posted. I had a few sprinkles of oil from my front seal. You could see them on the white inside of my cowling as a thin ring of oil spray. I moved my vent like Tom suggested and it (and a few other annoying drips) went away like magic.