Blow By Oil

Goat150 · #1 09-26-05, 02:15 PM

Hi,
I'm a new member of Skymaster Owners
and Pilots. And I hope I'm doing this right?
The 337H I have I has a 410 Hr Front engine and a 25 Hrs on the rebuilt rear that I paid to have done.

My question is I never had engine's with so much Blow By, The front engine is keeping the under side very oiley, and the rear engine I ran the blow by hose down and out by the fuel drain lines, just to keep the oil off the rear of the plane.
I've been told by two A/Ps that this is normal and to drop the oil down to six qts.
I'v done that and I guess it helped a little.
But I hate a oil leak and it's so hard to keep the plane clean.
Does any other owners have any thought.
Thanks
Mark

Ernie Martin · #2 09-26-05, 03:23 PM

You're on the right track, dropping the oil to 6 qts. Some minor leak is normal, but you seem to have too much. Get your A&P to clean the engines (my guy uses a compressor pushing a mix of air and gasoline), then run it awhile (either on the ground or in flight), then inspect both engines carefully to see if you can detect where the leaks are coming from.

Ernie

Goat150 · #3 09-26-05, 03:34 PM

Ernie,

I done all that and thats how we found out that the oil is coming out the Crankcase Vent. Some one said they thought there was a oil seperator that could be installed that dumps the oil back into the crank case ?

Thanks
Mark

big al 08 · #4 09-26-05, 05:00 PM

ernie is correct, it may take many times to find the source. degrease the engine and cowling, go fly the pattern. pull it all apart again and with lights and mirrors start looking. there may be several sources. case bolts are one, accessory case area, mags ect. degrease again and fly again. they are a pain in the ass to locate and very costly if you don't do it yourself. be patient it may take a lots of tries!!!!!!!!!!!!!!!!!

ps - also use finger to feel for oil

Ernie Martin · #5 09-26-05, 05:40 PM

If you reduce oil to 6 qts, you shouldn't need an oil separator. If you've got considerable oil after reducing to 6 qts and degreasing thoroughly, then it's not likely to be out of the crankcase vent. There ought to be a leak somewhere. As big al 08 says, degrease, run it, check, repeat, etc.

Ernie

Goat150 · #6 09-26-05, 06:43 PM

Ernie,

I'm so glad I'm now a member of the Owners and Pilots of 337s.
And you all have made me fill right at home.

Thanks One and all.

Mark

PS If I miss seeing a fly in of 337 Please some one tell me
about it, I would love to go to a fly in of 337 Pilots.

KyleTownsend · #7 09-27-05, 12:57 AM

I have been fighting oil leaks on the rear engine. I definitely have some leaks around the case bolts. But what can I do about it? How do you fix a leak around a case bolt?

skymstr02 · #8 09-27-05, 08:57 AM

Quote:

Originally posted by KyleTownsend
I have been fighting oil leaks on the rear engine. I definitely have some leaks around the case bolts. But what can I do about it? How do you fix a leak around a case bolt?

Do you have an A&P licence? If you don't, do you know a mechanic that trusts your work? The job requires knowlege beyond preventative maintenance, and a calibrated torque wrench.

Dave Underwood · #9 09-27-05, 10:03 AM

My experience as been similar.

I installed M20 Air/Oil separators a couple of years ago as there was blowby putting oil on the belly.

I can now run the oil level at 7 quarts both engines, and the belly is pretty clean, just exhaust staining.

That said, I still have a range of very small oil leaks from various push rod tubes which we are addressing as they appear.

As stated elsewhere, it is a process of elimination. That said, I would recommend the M20 units as they did make a difference and have cut oil consumption.

Regards - Dave

KyleTownsend · #10 09-27-05, 10:27 AM

"Do you have an A&P licence? If you don't, do you know a mechanic that trusts your work? The job requires knowlege beyond preventative maintenance, and a calibrated torque wrench."

I am working closely with my mechanic on this issue. He has a few ideas, but I would like to hear from someone who has actually solved the problem.

Thanks,

Kyle

skymstr02 · #11 09-27-05, 12:56 PM

A lot of the oil leak problems is that the oil is leaking past the string of thread that seals the crank case halves. I've had luck in taking the back bone bolts out, one at a time, alternatlly, using a q-tip swab and varsol, then MEK to clean the hole bore completely, squirt some red RTV into the hole, coating the bolt w/red RTV, and then assembling the bolt/washer/nut and torquing.

If the leak is coming from the case halfs themselves, then use a stainless toothbrush with the same solvents to thoroughly clean the split line area, and RTV that area. I usually use masking tape to make the RTV line neat. Most times, this required the removal of the throttle body assy and flow divider to gain access to the areas leaking.

I had one engine that had a persistant leak and it looked like it was the top seal on the pushrod. It turned out to be oil leaking around the rocker shaft retainer stud threads only when the head got good and hot. Never leaked on the ground runs, only after a flight.

Anyways, this is why I asked if you had a mechanics licence, because of the dis-assembly required.

Dale Campbell · #12 09-29-05, 09:16 AM

Hi Mark,
I also have a 337H and live right next door in Penna., so our climate is the same. I also had the oil on belly and tail feathers.
It is now much cleaner after putting M20 air oil seperators on both engines. I have two suggestions that worked well. Mount the M20 as high as possible, right against the top cowling. This allows oil to flow back to crank case without trapping at a low spot in oil line and not working properly. I would also wrap the entire oil seperator and oil line with insulation, so in winter the heat stays in line to keep it flowing and water condinsation does not form. Thats what I did and it works just fine. The only other leak I had was valve cover gaskets, which I replaced and push rod valve seals, which I replaced. My bird is now much cleaner. Good luck and safe flying. Dale Campbell

Goat150 · #13 10-05-05, 08:34 PM

Dale,
I installed the M-20 Air/Oil Seperators over the week end
and flew her from Ohio to Ga and back twice , Monday and Today
and I just want to say Thank You !!!! The seperators did the job.
I have NO oil blow by on the front engine at this time, and the rear has slowed down 99% , I even think I have a return fuel line leaking and not blow by on the rear engine.

Thanks to you I now can keep her clean!!

Mark

Dale Campbell · #14 10-06-05, 08:39 AM

Mark,
Thats good to hear. I installed M-20's on my 337H, 5 years ago and have been very happy with results. Happy flying and enjoy your bird as I do. Dale Campbell