The International Cessna^® 170 Association

Our 0 300 has started to leak oil and I suspect it is from the left mag flange joit but our engineer doesn't think so.
Afetr each trip I can wipe oil away from the bottom of the mag flange whereas the right is dry.
The engine was rebuilt last year and it has been quite oil leak free until two events that were undertaken at the same time.
The oil filter was very tight at the first oil change and removal turned the FM adaptor which had to be refitted with a new joint and crush ring.
(We think at engine rebuild they forgot to put lubricant on the filter seal and /or just overtightened it)
The left mag was removed and a replacement refitted.
Following this we get a good oil streak under the fuselage after each flight and drips onto the floor.

Our engineer doesn't think that amount of oil would come from the magneto joit area due to its location on the accessory case. and he tells us he replaced the magneto joint when the magneto was replaced.

We have wiped away the oil and ground run the engine for 5 mins with the covers removed (at no more than 1400 RPM)and the FM adaptor remained dry but nothing much appeared at the magneto flange area.
I tried this again today with the covers refitted and ran the engine for 10 mins with a good spell at 1600 RPM and it was possible to wipe oil away from under the magneto flange but then everything below was wet also.

Is it likely that oil can leak from the magneto flange area if the joint was not fitted correctly ?

Thanks
Bryce

Bryce - conincidentally, just finished replacing my spin on filter adapter with the Air Wolfe firewall mounted oil filter. Shortly after buying the airplane, several years ago, I had the spin on oil filter adapter installed. For the life of me I can't recall the brand name of the spin on filter kit, but it was the kit that involved two crush washers and resulted in suspending the oil filter at an angle off to one side. From the beginning, I noticed a constant oil mist on the fire wall and could not identify where it was coming from. Every time I changed the oil filter I would wind up disturbing the crush washers and wind up with a leak. It finally got to the point where I was replacing the crush washers every time I changed the oil and then the damn things would still leak. I have talked to other 170 owners with the same spin on oil filter kit and they say they experience the same leaking problem. My problem in identifying where the leak was coming from was the result on the blast tubes (for lack of a better discription) dispersing the oil so that it was difficult to identify the origin of the leak. It took spraying the back of the engine with developer to finally confirm the leak was the crush washers.

It is possible to utilize the incorrect magneto gasket. Lycoming gaskets will fit a Contenental, but they will leak.

Wash the engine with solvent and let it dry. Try running the engine again with Dye-penetrant Developer (Magnaflux developer) sprayed in the suspect area, and see where the leak originates. Baby-powder or common household flour is sometimes used for this task also, but the aerosol developer is a good method.

This is what the Continental gasket should look like (with brass grommets at the stud holes.)

Dye penetrant developer is a great oil leak detector, but Calcimine (or kalsomine) s a damn site cheaper!

As one who has "been there & done that", I can recommend going to a NAPA parts store & getting a bottle of their leak detector for the engine oil. It requires the use of a black light, but you should find out where the oil is coming from. This is likely what George is recommending and the dye is super cheap @ NAPA. Those pesky oil leaks can really be deceiving as to where they are coming from.

I have eventually tried the calcimine paint or as I have found it to be named here in the UK ,distemper,and the result was immediate.

see http://www.flickr.com/photos/27011563@N02/3759242040/

I am now hoping our engineer will investigate the leak and repair.