The International Cessna^® 170 Association

I have, according to the log book, a Cessna AK172-112F Oil Filter adapter on my O-300. There is a plug on the adapter in the center of which is drilled a hole of about 1mm. I believe the plug is for the oil bypass, but I do not have any drawings of the adapter to confirm its purpose. Any ideas on what it is? There appears to be an extremely small amount of oil on top of the filter, possibly from this orifice. This was only recently noticed because the whole engine compartment is very clean and has been for the five years that I have owned 56D.

Any comments will be greatly appreciated, especially helpful ones.

Bernie

I am currently troubleshooting the same problem, so I'll add what I know and see if anyone has any further advice.

There is a diagram of the filter adapter in the Cessna 100 Series Service Manual (1963 and later models). It shows an exploded view and gives general parts descriptions but no part numbers. Behind the plug is a spring and an isolation valve (I'm not clear on what it isolates, this valve is not the bypass valve). There is an O-ring on that valve that looks like the plug seals against. I am thinking that O-ring is bad. I removed the plug and looked inside. It looks like you have to remove the adapter from the case and disassemble the entire unit to get at the O-ring.

If anyone has been there before I would like to hear your experience before I start taking things apart.

Thanks
jc

This thread has been inactive for quite some time. I am currently dealing with a leak from the same cap so I thought I would share my findings/experiences with group.

1. Yes, there is a spring and by-pass valve behind the cap. The cap CAN be removed with the adapter and the filter installed. I recommend you drain the engine oil first. I then modified a 3/4' socket to provide a low profile along one side to fit onto the cap. Once the socket was modified, it was easy to remove the cap. the spring exerts a far amount on pressure on the cap, so as you remove it, be ready for it to shoot back at the firewall.

2. The part number for the o-ring behind that cap is not very easy to find. Abilene Aero, a Cessna Service center contacted Cessna HQ's to get the number for me. For Adapter 0556010-1, the o-ring is part number MS28775-113, If you have Adapter 0556010-200, the part number is MS28775-111.

Hope this is of help to someone.

Jughead

N2356D wrote:I have, according to the log book, a Cessna AK172-112F Oil Filter adapter on my O-300. There is a plug on the adapter in the center of which is drilled a hole of about 1mm. I believe the plug is for the oil bypass, but I do not have any drawings of the adapter to confirm its purpose. Any ideas on what it is? There appears to be an extremely small amount of oil on top of the filter, possibly from this orifice.

counsellj wrote:This thread has been inactive for quite some time. I am currently dealing with a leak from the same cap ... .

Jughead, It's interesting to see that in the 69-76 C-172 Service Manual in calls for welding the the hole in the cap shut.For reference I've added AK172-112F in the Mx Library.

Notice that they also remove the spring. Basically, it appears they are disabling the isolation valve to an "open" position.

Gary and George,

Thanks for the info and images you provided. My diagram that came with the filter adapter does not show the bypass valve in an exploded view. This was useful.

Jughead

Jughead,
I just ran across AD 96-12-22 which applies to your oil filter adapter. It looks to me like this is another AD that at first glance does not apply to the C-145 or O-300 because item (3) lists various Continental engines but not the C-145 or O-300. However, it says it applies to "Cessna Engine Oil Filter Adapters Assemblies, ... 0556010-(all dash numbers), ... installed on, but not limited to, the following: ... ."

Gary,

I have the AD, but thanks anyway, I'm sure it will be useful to someone else. We were just dealing with part number issues.

I'm impressed! That would be an easy AD to miss.