The International Cessna^® 170 Association

My engine is leaking a lot of oil and most looks like it's coming from the push rod tube seal at the case. Are these a big deal to change. Do you need to remove the cylinder or does will the tube slide back through the cyl. head to allow installation of the new seal.

BIG CAUTION HERE.

I had this problem about 12 years ago and it went on for about 60 hours before the cylinder cracked enough that the piston caught it and pushed the whole top of the cylinder off. The cylinder base and about one inch of the steel barrel stayed bolted to the case. That saved the case from distruction by the flailing rod. I got it on to a grass strip that just happened to be in the right spot but the engine had to be majored.

Do a cylinder compression test on the leaking cylinder. More than likely it will check OK. Mine did. That test is done with the piston up at top-dead-center and the valves closed. To check for cracks farther down the barrel, you must move the piston down by rotating the prop. Squirt soapy water on the outside of the cylinder. If it is cracked it will start blowing bubbles between the fins.

Because the push rods on the Continental engine are low and the rubber boots are a leak suspect, it is easy to miss this. I had 3 or 4 mechanics and experienced pilots look at mine over the 60 hours. We all came to the same WRONG conclusion---the push rod rubbers are leaking. Check for a cracked cylinder now. It is a lot cheaper to replace one cylinder than to do a complete overhaul.

Found the same thing on a Lyc. 0-320 in a friends RV-6. It kept spitting oil on the right rear baffle. Not much but we could not find a source for it. We did the soapy water trick with the piston down and sure enough, it was cracked on the top side about 1 inch from the base. The crack was about 1 inch long.

Call me about this if you do not understand the process. 513-569-7174 days or 513-231-3025 eves.

Good point, Gary. ANY oil leak is a warning sign. Don't make guesses. Find the exact cause before making the all-too-easy decision to live with it.
A cylinder is made of an aluminum head-casting which is threaded onto a steel cylinder barrel, similar to a cap-nut onto a bolt. After 23,455,633,151 compression stroke cycles, they loosen up and start to come apart. (Consider brand-new cylinders next time you do cylinder work.)
Several years ago, in my 206, I had a slight oilyness beneath a cylinder that I quickly decided must be a leaking valve-cover gasket. I put it off, thinking I'd replace them all at once next annual. A couple flights later the cylinder-head blew off just after take-off, at midnight. It's a bad feeling.
I've also had a cylinder check 72/80 on compression, and normally you'd be inclined to be happy and quickly move on to the next cylinder. I was mildly irritated at the mechanic who kept looking for the 8 lost pounds of pressure. (He didn't hear it at the crankcase, or the exhaust, or the intake.) I wanted him to just move on with the job.
He insisted on the soap-trick and found it bubbling at the joint of the head and barrel! That airplane was about to depart on a trip from Texas to Washington state. I hate to think of the possibilities.
With regard to the push-rod housings/rubber seals, ...
It's possible to replace the rubbers without completely removing the cylinder, but it's got a risk. If you remove the rocker-cover, remove the rocker shafts, remove the rocker-arms, remove the push-rods, loosen the cylinder-base nuts, slide the cylinder partially away from the engine, ....you'll have sufficient room to work new rubbers into place and reverse the process and bolt that cylinder back into place (onto it's old, tired cylinder-base O-ring) and hope it doesn't leak.
OR,...you can go ahead and slide the cylinder off just enough to push the piston pin out and leave the piston in the cylinder to save the old piston rings,...
OR,...you can completely remove the cylinder, inspect your piston, replace your rings (or cheat and re-use them ) ...and replace the lifter-cover gaskets while you're in there, (even examine the lifters if you want to) and put it all back together for only about an hour more labor.