0-290-D2 oil out Case Beather

[750-Miller]

It's not a Piper question but....If there is any group with a lot of experience with this motor that would know the answer to this one it might be you !

Picked up a Zenith 750 STOL with a 0-290-D2, ( came out of a PA-20 ). Am using about 1 Qt. every 3 hrs. Everything says that it is coming out the Case Breather. 200 hrs since overhaul , bottom plugs Clean, compression all mid 70s. breather tube drips, belly with Clean oil, inside the cowl is clean, oil level is kept between 5 1/2 - 6 Qt.... What's the best way , tips on how to sort this out ? Can the Breather Fitting on the Case be rotated UP to allow the addition of an Oil /Air sep. ?

[Vagabondblues]

the 290 series use two plain bearings on the front of the crankshaft. The combination of the two plain bearings and the location of the breather fitting to the end of the camshaft, create a lot of oil mist in the breather. Being that you are experimental, I would rotate the forward breather up and route the breather tube up over the cylinders with a gradual incline up to the accessory case. At the accessory case, I would drill through and tap threads at one of the unused bosses or pads like one used for the vacuum pump for example (at highest point possible, but preferably above the magnetos) and mount a AN Tee fitting the same size as the forward breather fitting. I would then connect the two fittings with the breather tube and run a new tube to overboard from the bottom of the tee fitting that was added to the accessory case. The breather air would then vented at two places, with the front tube at an upward angle. Any accumulated oil would tend to migrate back down the inclined front tube. And what ever made it up the tube, could be recovered into the added accessory case fitting. As I see it there would be no need to plug the front, (reduced chance or blowing the front seal) and no added cost of adding aftermarket breather at the rear case or even adding a nasty nitric acid recycling air oil separator. See attached christen inverted oil breather for fitting numbers, of course it will need to be a Tee.

[smcnutt]

We moved our breather fitting so that the line went up and over the engine. We also added a M20 oil separator back by the firewall. One or both seemed to have fixed the problem on our engine.

We originally had a small issue the grew into a royal PIA and that's when we finally did the above fix. in the process we discovered that we also had a failing wet vacuum pump that was dumping oil overboard. However, once the oil hits the slipstream it was impossible to tell exactly where it was coming from. As a test we put the end of the breather tube into a coke can and found out it wasn't coming out there. Did the same for the vac pump and figured it out quickly. We now also have a new dry vac pump but no oil on the belly from either place.

[Pacerfgoe]

Another possibilty is the cam could be slinging oil right from the end of the camshaft. If your going to turn the elbow so it vents over the top of the engine (as mine does,) pull the elbow right out and have a look inside. If you can see a slight bit (1/8") of the end of the camshaft sticking out, thats likely your problem. The fix is to pull the cam and remove (chop off) the extra bit that sticks out dress the end and reinstall.

[Glen Geller]

We moved our breather fitting so that the line went up and over the engine. We also added a M20 oil separator back by the firewall. One or both seemed to have fixed the problem on our engine.

We originally had a small issue the grew into a royal PIA and that's when we finally did the above fix. in the process we discovered that we also had a failing wet vacuum pump that was dumping oil overboard. However, once the oil hits the slipstream it was impossible to tell exactly where it was coming from. As a test we put the end of the breather tube into a coke can and found out it wasn't coming out there. Did the same for the vac pump and figured it out quickly. We now also have a new dry vac pump but no oil on the belly from either place.

Good ideas! On my PA22-150, I tend to get a good bit of oil on the belly and left LG leg.
I have tinkered with vent tube exit position from both crankcase breather and oil separator, added the whistle hole to reduce effect of low pressure up the tubes, and thought about placing a tin can over the end of each tube to find the offending component. My wet pump (Pesco I think) looks like it sailed over on the Mayflower, so I guess I should start learning more about those.

GG

[wyandot jim]

We also have a O-290-D2 in a 7GC Champion. Yours appears to be throwing way to much oil out the breather from blow by. 1 QT. every 3 hrs. seems way high to me. Yes ours does drip some on the floor after flying, but does not make a mess on the belly, some after several hrs.. It now has 5-600 HSMO and we have flown it SMO. We run it with 5-6QT. and it uses about a QT every 15 hrs. or so. It has chrome cylinders. To be honest I never paid much attention to how the breather is routed. I guess I will look this weekend.
Jim

[750-Miller]

Definitely came to the right place ! THANKS to Everyone... Lots of good ideas ALL pointing in the same direction.... There is a cure / betterment in sight...

Just back from the field and have one more thing to add that could be a factor .... The breather tube is now rigged to extend Below the Cowl and sticks out into the Slipstream... Could be creating a partial vacuum all the way back to the Case , ( the old blow over a straw and watch the water rise trick ? ) , which is already pushing air & oil mist out into the line. Have room to cut it back above / inside the cowl and still be located Below the belly at the exit point....

Thanks again , and additional thoughts appreciated.

John

[wyandot jim]

AHHHHHHHHHHHHH I do believe it should be below the cowl in the slipstream and have a vent hole up higher in it also. The vent hole is supposed to keep it from creating a vacuum.
On my Starduster I ran the vent all the way to the tail and it doesn't create a vacuum so who knows???

[Vagabondblues]

[QUOTE=The vent hole is supposed to keep it from creating a vacuum.[/QUOTE]

The vent hole is called a whistle slot. Its purpose according to lycoming is to prevent freezing of the breather tube during winter.

[750-Miller]

The vent hole is called a whistle slot. Its purpose according to lycoming is to prevent freezing of the breather tube during winter.

Think I have a handle on the Path for the line.... Rotate the Vent fitting up, bring the line over the top of the motor and cross to the right side, (oil cooler is at the back on the left side ), then through the back baffle, and reattach to the Vent pipe, (already in place between the the back of the motor and the firewall ).

For now Keep the vent pipe long ( ? ) into the slipstream ( Did a quick walk around at the field and looked at where vent pipes were coming out Cessna, Piper and another Experimental... all terminated above the cowl.... ) , AND if not already there drill a whistle slot ( 1/4" ? 3/8" ? ) in the 3/4" vent pipe above the cowl but below the belly...

With the Case Vent fitting re-positioned up, the oil separator made by Airflow Systems could attach, with vent hose coupling, directly to the case fitting and then run the line back. That unit requires a 15 degree down angle on the intake , back towards the case, ( attaching to the vent fitting will provide that ). Being that close to the exit point should keep the separator from freezing any moisture at that point ( ? )