Oil Leak Hunting

[dstates]

Well, my oil leaks were starting to get a little embarrassing when parked on the ramp and even drove me to get a new creeper since I was cleaning the belly of the plane so often. I was pretty sure that I knew where the main leak was coming from, but I wanted to rule out any sort of case crack or more concerning leak origin. With the approval of my A&P IA I added a fluorescent UV dye to the oil. After a thorough cleaning of the engine I ran it on the ground run a total of 4 times. First run was short to see the beginnings of leaks and then ran additional time in order to make sure I found all of them. I'm attaching some pictures.

My main leak is at the #3 cylinder lifter housing gasket. I'd guess my second worst leak was from the quick oil drain. Third is probably a three way tie between the starter, right magneto and the #1 cylinder lifter housing. I also found a couple drips in the generator and minor evidence around cylinder base flanges.

I've already started on replacing the o-rings in the quick drain valve and will hopefully get the #3 lifter housing gasket replaced this weekend. I will likely save the other leaks for the non-flying season this winter during my annual inspection.

Just wanted to share how evident the leaks are with the dye and a UV light (black light). In the pictures the purple is from the blacklight and the leaks are sort of a turquoise green.

Doug

#3 Cylinder Lifter Housing

#3 Cylinder Lifter Housing (closer view)

Quick Oil Drain

Starter

Magneto

[dstates]

#1 Cylinder Lifter Housing

Generator

UV Dye

[GAHorn]

When you decide to address the cylinder-lifter housing… I did this to an O-300 that had a similar leak. It turned out NOT to be the GASKET at all. It was the lifter housing itself which had an almost invisible crack, found only with dye-check penetrant. (I showed this housing at the Cody convention mx seminar.) These housings are not robust and if one is careless in not using an inch-lb rated torque meter and carefully, evenly torqueing them when installing them…they can be cracked.
As further insurance against a gasket leak I smeared Permatex #2 non-hardening gasket paste on the gasket.

This housing can be changed without completely removing the cylinder if one is careful not to disrupt the cylinder-base O-ring seal. FIRST, Remove the key, ground the mag P-leads with jumpers, and DISCONNECT the aircraft battery!…. Then pull the spark plug leads on the cylinder and place the offending cylinder piston at TDC. This will relieve valve spring pressures and also allow the cylinder to be pulled away from the crankcase without exposing the piston and rings and thereby save them instead of having to replace them). Loosen/remove the exhaust riser and intake elbow/hose Then loosen the cylinder base nuts/through-bolts and pull the cylinder away from the crankcase only sufficiently to R&R the lifter-housing. This also allows room for the rocker arm shaft to clear the adjacent cylinder. Be careful not to pull the cylinder too far so as to expose the piston and rings. Be prepared with safety-wire, etc. to hold the cylinder UP to keep it from falling as you continue the job at hand.
Remove the rocker box cover, slide the rocker shaft aside to remove the rocker-arms and pull out the pushrods (keep them AND the rocker arms oriented for exact reinstallation).
Reverse the procedure for reassembly using new gaskets and remember to install new pushrod rubber seals BEFORE sliding the cylinder back onto the crankcase….. And don’t forget new rocker box gaskets, intake and exhaust gaskets, etc.

It took me about 2 hours and the engine has remained in-service without further difficulty.

[dstates]

George, thanks for the heads up that it may be the lifter housing. I'll definitely inspect it carefully.

I have the Real Gaskets pushrod tubes STC so I will be able to replace the housing by just removing the rocker cover, rocker arms, pushrods and then pushrod tubes. I won't be touching the cylinder base nuts.

Doug

[GAHorn]

George, thanks for the heads up that it may be the lifter housing. I'll definitely inspect it carefully.

I have the Real Gaskets pushrod tubes STC so I will be able to replace the housing by just removing the rocker cover, rocker arms, pushrods and then pushrod tubes. I won't be touching the cylinder base nuts.

Doug

That will definitely make it easier as long as you can get the rocker arm shaft out without conflict with the adjacent cylinder… it should work.

[dstates]

That will definitely make it easier as long as you can get the rocker arm shaft out without conflict with the adjacent cylinder… it should work.

It slides right over enough to get one out then you slide it the other way to get the next one…

[GAHorn]

Yep… that’s what you have to do on cyls 3 & 4 ….and notice that the exhaust rocker has an oil-squirt hole and while the intake may have a similar provision it is not required…. the point being not to mix the them up…keep them in the same relationship along with their pushrods.
While you’re “in there” …take a very close look at the rocker-shaft “boss” or “ears” to be certain there are no cracks. I’ve never seen it on these smaller Continentals but it’s been an issue on the larger ones.

[dstates]

Yep… that’s what you have to do on cyls 3 & 4 ….and notice that the exhaust rocker has an oil-squirt hole and while the intake may have a similar provision it is not required…. the point being not to mix the them up…keep them in the same relationship along with their pushrods.
While you’re “in there” …take a very close look at the rocker-shaft “boss” or “ears” to be certain there are no cracks. I’ve never seen it on these smaller Continentals but it’s been an issue on the larger ones.

That’s a good reminder on the bosses. One of handful of reasons I don’t want to remove the cylinder is the AD that would require sending out the cylinder to inspect those bosses if the cylinder is removed.

I’ll have this back together soon. I didn’t realize it until yesterday but I’m short one seal and with the holiday won’t be able to get it till Wednesday. Of course the weather here this weekend has been gorgeous.

[dstates]

After a good visual inspection of the lifter cover housing I got everything cleaned up and re-installed.... only to find that it leaked again...

So, this drove a closer inspection of the lifter cover housing. My A&P did a UV dye penetrant inspection. He found a crack. I don't have pictures from the inspection, but the crack is located in the area circled. I have a new lifter cover housing coming my way from Fresno Airparts Co. Hopefully I only have to put this back together one more time.

[GAHorn]

When you decide to address the cylinder-lifter housing… I did this to an O-300 that had a similar leak. It turned out NOT to be the GASKET at all. It was the lifter housing itself which had an almost invisible crack, found only with dye-check penetrant. (I showed this housing at the Cody convention mx seminar.) These housings are not robust and if one is careless in not using an inch-lb rated torque meter and carefully, evenly torqueing them when installing them…they can be cracked. …..

Yep…. it’s surprising how such an almost invisible crack can make a huge leak. On the O-300-D I spoke about earlier…a similar crack was discharging about a quart every couple of hours.

[dstates]

Well, I replaced the lifter cover/housing with a new one and still have the same leak. It is hard to tell from this latest picture, but when examining in person the corner of the lifter cover gasket looks dry. Any chance it is coming from the through bolt right next to the lifter cover (behind the ignition wire in the picture)? Or maybe just coming down through that area from the base of the cylinder??

I’m about to give up on this one and deal with the mess.

[GAHorn]

You’ll have to use some solvent/cleaner to clean the area and then run it again to see exactly where it’s coming from.

Many of the studs do penetrate to the sump and oil can find it’s way out… but depending on how long you ran this in the test it’s difficult to answer your question…and the pic does not show the area of the cylinder base very well (poor lighting).

One way to detect this is to clean and dry it with solvent or electronic cleaner…. then spray developer into the area to coat it…next run the engine to see where it gets wet first. (Some of the old geezers used all-purpose flour or baby-powder)

Magnaflux developer available at Amazon

The fact you had a crack in the lifter cover certainly contributed… but I wonder who/when and how the engine was last assembled….hoping whoever it was …. was competent and didn’t do something stoopid like use an impact wrench.

If you can determine it’s a thru-bolt or stud that penetrates to the sump…. I can say I’ve successfully stopped such leaks by cleaning the stud with aerosol electronics cleaner and forcing Permatex #2 into it with a popsicle stick/tongue-depressor, then placing the flat washer and nut back onto it and torque-ing it properly while the permatex is still “wet”. Let it dry overnight. (Fixed my left/forward engine-mount leaks that way when I first bought my 170 and it’s still dry….. at least in THAT location.)

I buy this stuff at WalMart by the carton and use it on lots of things very successfully (including getting the grease-gun mistake out of my favorite shorts before Jamie finds out I’ve been working in good clothes instead of my junk trousers. great stuff!). It’s also safe on most plastics.

Lowest priced at WalMart automotive department

[c170b53]

Good one George, we use the same technique. Clean the inspection area well, let-it dry, spray the developer and observe after a short duration.

[ghostflyer]

Thanks George , I am not a old geezer but have used the baby powder for years very successfully . [on the aircraft] A paste made up of water and baby powder and is painted and let dry. The engine is run for a short time and then checked. I had a oil leak on my engine originating around my R/h mag. It used to flow very freely down to my tail wheel . Tried everything including die penetrate ,baby powder ,camera in the engine compartment. Just couldn’t find it. It seemed to appear in mid air. Near the mag. It was when the engine was being removed off the aircraft and mags being removed that it was found that the top stud even thou it was tight and correctly fitted the oil was passing through the top of the tread screw lands and passing through the spring washer. A incorrect heli oil had been fitted.