I'm having my O-540 A1D5 overhauled on my 1960 PA24-250. Per the advice of my shop, they suggested I ditch my air-oil separator and go back to the factory setup of the engine breather tube assembly. The problem is we can't find one. We can likely fabricate one, but if someone had one I'd be interested in it.

Out of curiosity, what is the motivation to ditch the Air-Oil separator? Is it causing a problem or not doing it's job? We have one on a Cirrus and it keeps the belly cleaner. There is however a 100hr ICA for cleaning it.

- Charles

The air/oil separator definitely keeps the belly cleaner and I may miss that. However, it continually puts high moisture content air/oil back into your engine and sometimes not quality oil or contaminated oil. Consequently, creating a more fertile environment for corrosion and possible other issues. My mechanics thought it would be best practice to not put that type of oil back into a fresh engine. Plus I've seen some of that stuff in the air/oil separator and wondered why the heck I was possibly rerouting that back into my engine.

I have heard this statement as well about air/oil separators. I can't verify it with science but years ago when I had an O-540 overhauled at Poplar Grove, they shared this belief of high moisture content being returned to the engine as well. I suppose some would consider it inconvenient but personally I am in the habit now of literally spending just 5 minutes tops of squirt/squirt, wipe/wipe on the belly after each flight or two and my belly stays nice and clean.

Ed

Tom,
We have a 61 250 with the same engine, 0540-A1D5.
Would you mind posting how things are going with your overhaul? We are at 1800 so we are getting close. Did yours make TBO? What was the decesion to overhaul? Any information you wish to share would be most helpfull. Thanks

Andrew

I'd like to know that answer too. My '63 Comanche 250 with the O-540A1D5 engine now has 2100 hours on it. Still running strong but the time is coming for an overhaul. Would like to hear who you went with. My initial taught is to put a reman from AirPower in mine. Cheers

Alan Cheak

Andrew and Alan,
Between my A&Ps and myself we had been watching the engine closely. I've had the oil analyzed ever since I bought the aircraft about 9 years ago. I've flown it about 1200 hours in those 9 years and we basically we're watching some parameters on the engine amongst accessory issues as well ( wiring harness, mags, hours on exhaust stacks/muffler, prop, etc). I had about 1850 hours on it,TSMOH. Essentially when I brought it in for annual in October, I had 3 cylinders that had dropped compressions into the 58-60 range. A significant swing from the 68-72 range one year earlier. In addition I had some consistent metals in the cautionary range on my last 3 oil changes, mainly chrome from the cylinders. But some others too. Bottom line, it was time. I don't need to be in IMC with my family onboard and have a engine get "terminal" on me. Got to have confidence in the ponies up front.
So, I'm doing basically a firewall forward. I am doing an overhaul of the current narrow deck engine rather than the Lycoming factory reman. I'm not convinced of the value of the roller tappet technology. Every shop I talked to, Penn Yan, Johnston Aircraft, Buldoc Aviation, and others told me that given the number of hours I fly, I wouldn't see a difference in smoothness or performance. You all have to do your due diligence, but I'm confident I will have a very good engine up front and keep at least $7000 in my pocket. The engine overhaul itself including, carb, plugs, harness, new starter, mags, and new Superior cyl is going to be about $27,500. The 3 shops I mentioned above were all pretty close and come with great reputations. It came down to convenience/shipping because Buldoc is close to where I live in MN.
With the rebuild on my exhaust, engine mounts, alternator, oil cooler, all new hoses with fire sleeve, propeller, governor, baffling, and I'm sure other things, plus labor, I'm looking at a total with the engine of $37,000 right now. So far I'm on budget track. If I get done for $40k or less I'll be happy. My engine should be done in about two weeks. Given Christmas and New Years in there, I hope to have "the other woman"( as my understanding bride is fond of calling the Comanche), back in the air in early January.

Tom,

I've had to build a replacement breather tube before, the trick is to keep the tube from collapsing as it is shaped. I filled the aluminum tube with 1/16" mild steel welding rod prior to bending, it worked very well, then a Parker bearing tool for the ends. After its the correct shape, pull the welding rods out.

Clarence

Clarence,
That's a great tip. thanks. We had not done it yet but I think the tubing just arrived at the shop. My mechanics said they've used sand packed into the tubing in similar situations. But the welding rods would be easier to keep stabilized in the tube while bending. I've sent them a copy of your post.