I am flying a 1969 Debonair with a continental I520. We are chasing an oil leak on the number 5 cylinder. We have replaced the seals twice and the pushrod tubes and springs once. The last flight was for 3 hours and we lost 1/4 quart of oil. We have dye in the oil.
Let me know if anyone has any ideas on how to fix my oil leak?
Thank you in advance for the help!
Eric
With #5 which is the right forward cylinder, we have seen leaks around the alternator gasket migrating aft under the #5 cylinder. Also, make sure that you do not have a leak around the base gasket of the cylinder or possibly a cracked crankcase around #5 or #3 cylinders.
A good way to locate a leak is to wash the engine and compartment down completely and then let it dry. Take some baby power and dust the areas where you think the possible leak is located. It make it easier to see a very small leak.
Bob Ripley
ABS Senior Technical Advisor
With 1/4 qt in 3 hrs it is hard to tell how much is normal oil consumption and how much is leak. I agree with Bob about cleaning and dusting with baby powder. I have never used baby powder but now may try it. In the past I have used the white dye penetrant developer as it sprays on and you may be able to get into more nooks and crannies.
I also am leaking oil from #6 cylinder. It appears to be coming from the lower screw hole of the rocker cover....
I’m seeing the most buildup there, as well as dripping below on the “access panel” Beneath that cylinder. Do the rocker gaskets deteriorate often.....? I also just overhauled the prop governor , yet it appears bone dry. Thanks in advance.
Hopefully the baby powder trick will allow you to find the source. I have used that method and it works surprisingly well. I had a similar oil leak on the number 4 cylinder. My AI was absolutely convinced it was pushrod tube seals until replacement changed nothing. It turned out to be a crack starting at one of the studs and headed for the next stud. If it had not been caught, there is a good chance the cylinder may have departed as the crack advanced. The way we found the crack (only really visible once the cylinder was removed) was by checking the torque values on the cylinder head nuts. The one with the origin of the crack had almost completely relaxed.
The picture you sent of the alternator is looking up, as best I can tell, at the cooling air exhaust vent that exits the bottom of the alternator. You can get oil there, so that is someplace to check. The real place to check for what you are describing is for oil leaks around the base of the alternator where it bolts to the engine. The lower aft bolt is often hard to access, so it may have a higher chance of leakage past the gasket due to under torqued fasteners. Check them all though.
How old is the engine? If the alternator is not the source, check the cylinder base. Unfortunately, many engines, as they age, will have the sealant/locking compound between the cylinder studs and crankcase dry out and permit oil to weep along the stud. This is outside the cylinder base seal, so will weep out past the cylinder base and show up on the pushrod shroud tube springs and gasket at the oil sump/crankcase junction.
