A65 oil pump losing prime

[radiotek]

Had not flown my '46 chief for about a month and when I fired it up, no oil pressure. I got it back by pumping a few ounces of oil into the oil pressure guage hose and after that it came right back up and was OK for subsequent flights. I have experienced this in the past after changing oil and cleaning the screen where you evacuate most of the residual oil in the system but never after just letting the plane sit for a while. Wondering if this is normal or do I have wear in the pump or what? Thanks!

Pat

[Champ99b]

It sounds like the gears, housing (acc case) and backplate are worn.

I had the same problem after measuring all each was within tollarances but the accumilation of all didn't meet it. I fixed mine by replacing the acc case and new gears everything works great now. I don't remember who I talked to but they could rebuild the acc case but it was almost as much as the new one (C-90 engine) and a 8 week turnaround. It might not be all that are worn but you will not know untill you take it apart.

I hope this helps

Ron

[joea]

Agree with Ron. This usually means that the accy case oil pump is getting old.

Another way to take care of this is to raise the tail on the airplane, but frankly without two people this can be a PITA.

Best is just to fly more often!

Joe a

[MikeB]

We've had good success with Bolduc at the Blaine County Airport near the Twin Cities. They bush the case which keeps the gears in line. The big problem with the A65's etc is the 'driven gear' is not supported at both ends which allows the gear to 'hang down'. I've sent two out for the case repair and it solved the drain down problem. My Champ sat for about 5 months this past winter and the oil pressure came right up. Before I had to prime the pump by pulling the oil temp sender and squirting oil in it. I suppose it depends on how worn the case is but it worked for us. The fix isn't cheap, around $400, but included the repair, new gears and end plate. Most of these old timers seem to have the oil pump wear problem. I think that's why you see a lot of used accessory cases on EBAY

I think (actually I know) the problem could be solved by supporting the driven gear at the end plate but I don't know if anyone doing a legal fix like that yet.

MikeB

[Roger Anderson]

Had not flown my '46 chief for about a month and when I fired it up, no oil pressure. I got it back by pumping a few ounces of oil into the oil pressure guage hose and after that it came right back up and was OK for subsequent flights. I have experienced this in the past after changing oil and cleaning the screen where you evacuate most of the residual oil in the system but never after just letting the plane sit for a while. Wondering if this is normal or do I have wear in the pump or what? Thanks!

Pat

Mine does the same thing maybe several times a year, usually after an annual, its been sitting, and the prop has been turned numerous times by hand. Just be sure to always check oil pressure right after start up on A65s. It's just an unfortunate nature of these engines. Whereas it would be nice to pull the accessory case and have the oil pump rebuilt, just being aware of the issue works just fine for me. I've flown this A65 about 700 hrs now and this is only a mild inconvenience to watch for. Joe's right. The tail of my Chief is getting heavier and heavier to lift. Couldn't be me getting older and older could it? Oh....if you don't want to lift the tail beyond horizontal and let the oil drain out of the oil screen cavity down on to the gears to prime them, it might be easier to unscrew the oil temp prob instead of the oil pressure gauge line and squirt a few ounces into it. It then will drip down onto the gears and prime them.

[Captgrumps]

Most cases have scoring wear on the aft side of the gears after years of use. I am putting an engine together and having rear case repaired. As previous mentioned it cost about $400-500 to have it done. This includes new oil pump overhaul kit (which includes gear plates and etc) and what else needs to be done.

Doug

[Aerco]

What kind of paperwork does that kind of re-working of the cases require, if any? Since I will be pulling apart two of these engines in the future, it might be worth getting done. I have access to a pretty good machinist here.

[joea]

Unless your machinist is with a FAA certified shop, doubt that he can legally do a repair of this sort.

After having some thing like this done the accy case needs to be returned with a yellow tag that certifies that its legal to install on the airplane. This is of course unless the plane is Experimental.

[jack duncan]

I've had this problem too before I overhauled the engine, but before I overhauled it, I put a T- fitting at the oil line where it connects at the firewall, and simply unscrewed the cap on one side of it and squirted some oil in to achieve pressure, worked for me.

[DC Krog]

I am surprised it hasn't been discussed in the past but there is a service bulletin concerning loss of oil pump prime in larger Continential engines. Their recommendation from the service bulletin is to basically seal the pump cavity/cover plate like you seal a crankcase. Use silk thread and non-hardening permetex (coat sealing areas very lightly)

This seemed to fix a large amount of overhaul and later service problems on large Continental engines. What is interesting is CMC lack of interest in older/smaller Continental engines.

If I had this proplem I would try fixing the old pump cover with silk thread and go from there. I think the old pump plate is drooling out the needed oil from gaps between the plate and accessory case due to the angle at which the airplane normally sits.

[joea]

If I had this proplem I would try fixing the old pump cover with silk thread and go from there. I think the old pump plate is drooling out the needed oil from gaps between the plate and accessory case due to the angle at which the airplane normally sits.

My concern would be where in the Continental Maintenance manual does it show a "silk thread" repair method?

Unless we are talking about a experimental aircraft, using any "non-approved" method is not allowed. Not disagreeing with you, just pointing out the legal issues.

[Champ99b]

Joe I agree.

Where would you install the thread? the oil doesn't leak around the seal, it is the wear on the edges of the acc case and the plate where the edges of the gears have been touching and wearing for all the years and hours in the past. The leak is not on the sealing surfaces between the acc case and the plate, this area does not move on either unit.

In my opion either let it alone or fix it right. It may not be your life only that you will save.

Sorry I got on the soap box again. hehe

Ron

[Paul Agaliotis]

Ron,
The wear is in the oil pump shaft holes.
Nobody warms their engine and the cold oil puts a lot of stress on the aluminum holes. As the holes wear the gears start to touch the edges of the pump cavity.
For the C-12 series I would buy new, the A series you will need to fix. There has been some C-12 series gears and cover installed into the A series but I know of no approval.
Paul

[Champ99b]

Thanks for the claification Paul

I have a C90-12 in my champ. That is what I was going by. The replacement of both the acc case and gears was a perfect fix for me.

Ron