Thorp Air Command - T18.net

I have an 0-290d2 in my s-18, crankcase breather tube has always leaked oil on the belly. I have removed cyls. 10 over steel w/ crome rings and sent to firewall forward to be deglazed and new rings, after 18 hrs.w/ 40w mineral oil at full throttle flying at low alt. and temps. above 40*f I still get alot of oil on the belly. Breather tube is mounted at the rear of the eng. on assy case. I'm sure rings have seated by now. Has anyone got any ideas. Full throttle flying is about to break the bank? I do have an oil air seperater but don't really want to put it back on!

Mark,
How much oil are you putting in the sump? For my O-290 I only fill with 6Qts. When I first had the airplane 2 Qts went overboard on the first 2 hour flight, after that it took 23 hours for the next Qt. Lycoming states that you can operate the engine with 2 Qts in the sump.

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Bruce Finney
N18JF T-18C #262
Yelm, WA USA

Changed oil at 11.2hrs. and put 7qts. in, after starting eng. to leak check and fill the filter it showed 6.5 qrts. on the stick. In 7.5hrs. of flying it, it is down to 5.5 qrts on the stick. when i go to fly it again the oil film on the belly will have left spots on the floor under the belly from the crankcase vent to the tailwheel. looking back in the log book this has been a problem from the first time it flew. I thought the rings had never got seated in properly. I will let the oil level go on down a little more and I've been told that if a dip stick leaks air by the gasket that it could couse this. I'll put a 0-ring under it and see if that helps. It makes me wonder if the cam gear that is just below the cc fittingin the assy case is throwing oil out of that vent????? Maybe move the cc vent to the front of the motor?

If you have a,hose for vent, it needs a small hole punched in it at the vent fitting to prevent sucking oil out of the,case.

** admin posted for Bill Williams ***

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Forum Administrator

Thanks for your input Bill, I just came from the plane and put a o-ring under the dip stick, the hole your talking about, how big and at what position on the fitting. 12 Oclock or what?

3/16 hole located in the(on top) rubber hose where it connects to the case. mine is located about 2" from the fitting on the top of the hose. Anything to break the vacuum

*** admin posted for Bill Williams ***

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Forum Administrator

Thank you Bill, I'll let you know if it works, It will be a few days before I can get back in the air, Weather!!

The 290's are notorious for blowing alot of oil out of the breather. I moved mine from the accessory case to the front location and it helped some. Also have always used an air/oil seperator. I have let mine go down to about 5 quarts and the rate at which it goes overboard decreases with the oil level, but it still blows alot more than other model engines.

I have had three different sets of rings in the engine over the years and always blew oil. Plugs have always ran very dry so the oil is not going by the rings.

What is the compression now?

Bernie Fried
N18xs

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Bernie Fried
N18XS

A little oil goes a long way, for years I have been trying to find a way to reduce oil on the belly of my T with an 0 290 , the tip with a hole in the top of the breather line sounds like the next thing to try,
thanks Bill.

Lance N38DT

TALK ABOUT BLOWING OIL, BEFORE JERRY HOOVER FLEW HIS PLANE I TEST FLEW IT AND IT WAS BLOWING OIL OUT OF THE FRONT BREATHER OF HIS FRESH 0-290 AT ABOUT 1qt+ EVERY 15 min. NEEDLESS TO SAY THE IT GOT OUR ATTENTION FAST. AFTER PROLONGED EFFORTS TO COME UP WITH A SOLUTION, JERRY BIT THE BULLET AND PUT ON A ACCESSORY CASE WITH THE HOSE VENT AND THE PROBLEM WAS SOLVED. I SUPPOSE THAT THE GUY WHO BUILT THE ENGINE DRILLED THE HOLE IN THE WRONG PLACE???? AFTER A FEW OTHER BUGS THAT WERE SOLVED THE PLANE FLEW GREAT. DO NEW PLANS HAVE A HOLE IN THE VENT TUBE? PAUL MACMICHAEL

Thorpdvr, thanks I have not done a comp. test on the 290 yet as i have only 19 hrs. on new rings. I should check that to see if rings have all seated yet? I have put an o-ring under the dip stick, witch it did not have? I will put the oil seperater back on it and run the drain into the exsht. pipe and burn what comes out? I might run the CC line back to the frt. of the eng. to. Some one said to drill a 3/16 hole in the cc line 2" behind the fitting at the assy. case, I'll try that also. I don't know if these cyl. have choke in them so that could be some of the problem to. So I guess I'll just burn the oil or catch it in a res. and empty the res. when it fills up. thanks for everyones help! I plan on putting an 0-360 on it soon so I'll put up with it until then, thanks.

Hey copterplt, I've got thousands of hrs. behind R1340s and R985s and this little mouse mtr. dumps out about as much as they do???? Well maybe not as much but close. LOL

You could also run the breather tube down the leading edgw of your gear leg fairing and out the bottom of the wheel spat. That way the oil does not spoil the belly . Just my 2cent worth

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James Ball

Jtball, Thats how this plane was set up when I bought it in Aug. every time I shut the eng. off it would make a puddle on the floor at the right tire from the oil/air seperater drain tube. I could plumb it into the crank case but I don't want that humid milky looking stuff back in the eng.

Tom Hunter had a brilliant idea that is currently mounted on Dick Wolff's T-18 - the breather tube was shortened and the end placed through a hole in the screw on top of an aluminum coffee travel mug mounted longitudinal with and to one of the lower engine mount braces that intersects the gear leg at the bottom of the cowl - the coffee cup contained plastic "brillow pad" material to prevent sloshing - I would drain perhaps 4 fluid oz at each 25 hour oil change - that doesn't solve the amount of oil exiting your case, but it sure saved time cleaning the belly, and having the tube in the coffee mug prevented any suction from occurring.

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Fraser MacPhee
N926WM
Serial #279-1
Angel Fire, NM (KAXX)