oil leaks - dye test

I finally got around to using the UV dye and flashlight to find the oil leaks in my engine. I bought the stuff at Autozone for $20. $6 for the dye, and $14 for the UV flashlight and yellow goggles.

Anyway, I ran the engine for 15 min. to get it up to operating temps (wasn't hard to do since it was 100 degrees today), then put the airplane in the hangar to look for leaks. I found a few small ones. One (each) of the pushrod tubes for #1 and #3 cylinders appears to have a very slight leak at the crankcase. The rubber gaskets don't appear to be doing their job. Is it OK to use gasket sealer on these?

I also found a slight leak on the copper nut on the bottom of the #3 cylinder. Actually, that one started leaking from day 1. I've never been sure how to stop it, so I just left it. Any ideas?

There were also a couple of flourecent spots around the rubber hoses connecting to the oil drain-back lines. This surprised me since before doing any of this I re-tightened all the hose-clamps I could find. I'm wondering if anyone ever adds a slight layer of gasket sealer to these?

The only other thing I did was re-do my crankcase breather hose. I wasn't happy with it before, and ended up making the new one exit the cowl like a mini-exhaust pipe. I'm really hoping this creates a negative pressure and slows, if not stops, my leaks. I'll report back with the results after I fly it a couple hours.

Did your redirection of the breather line help? I am seeing similar "leak" and am going to give the dye a try and see if I can narrow it down. It seems that I too have a cylinder base o-ring that is not doing its job. I also redirected my breather line out the back of the cowling.

Hi Tony,
I did redirect the breather, but I'm not sure it helped. I still seem to have a small oil leak somewhere. It doesn't register on the dipstick, but the lower half of the engine has an oily mist on it (still).

Did you try the "dye". I am looking at that online right now.

Yep, I still have the dye in my oil. I'm not sure if it works that well, though. In a dark hangar with the UV flashlight, it's still hard to find where the leaks are...and I'm sure I have a leak somewhere! Maybe I was hoping for something really obvious, but so far, it's not.

Update

Well, I think I found my oil leak. I'm still not 100% sure so I'd appreciate some feedback from you engine guru's out there.

I read somewhere that builders were putting fuel lube on the pushrod tube shroud seals to help prevent minor seeps, so I took off the rocker covers, slid the tubes out a bit, cleaned things up and added a thin layer of fuel lube to the crank case side of the shrouds. The picture below doesn't show the whole mess, but essentially there's dirty brown fuel lube around all of the pushrod tube seals along with a nice thin layer of oil over the top of the crank case.

One thing I've always noticed about my engine is that those seals seem to stick out more than the seals I've seen on other engines. I can also push on them with my fingernail and slide them in a bit...they don't seem to be sealing very well at all. If I had to guess, they leak more than I originally thought.



One other thing to note is that the round o-ring on the valve cover side is very thick. I'm wondering if it's the wrong size and doesn't allow the shroud to seal very well on the crank side. Or possibly I have the wrong seals on both ends of the shroud. I used the o-rings that came in my engine kit, but I'm starting to think they're the wrong ones. Any ideas?

I cleaned up my engine really well and ran it. It appears that all 4 cylinders are leaking (weeping) at the base. When I assembled the engine I lubed the o-rings with o-ring lube and now I am thinking that that has caused them to leak EEEK!

So now I am faced with either a messy cowling/engine for the next umpteen years or pull 4 cylinders and replace the o-rings.

I have heard some engine builders have used lube with good results and some have had bad results. It seemed like a good idea at the time, now I wish I would have installed them dry.

Anyone with some insight on this?

Sonny - I did use fuel lube on my push rod tube seals. I think that is the way to go with them.

Another update: I spoke to ECI today and they said that it's likely that I have the wrong o-ring at the rocker side of the push rod shroud. OK, so I ordered new ones...we'll see if this helps! It may be $16 well spent.

Another update

I hope this helps someone else that may have this problem. I got my new push rod shroud o-rings in and installed them today. They were the same size that I already had in place, but I went ahead and pulled the rocker arms off and swapped them out anyway.

At first when I installed them I was disappointed that they seemed to fit the exact same way on the engine side. They were showing about 1/8 of an inch and I could move them with my thumb nail. The valve side seemed fully seated, and I grabbed the shroud and tried pushing it on further (like I'd done many times before), but it didn't seem to budge. Then, I wiggled the shroud a little bit and it popped into the seat at least another 1/16-inch. All 8 pushrod shrouds were the same way, and would only seat when it was wiggled.

Awesome

The push rod tubes must be machined to a tight tolerance, and just needed a little persuasion Glad you figured it out! I'm working on my gear leg fairings, so you will soon see nothing but my rear strobe!

I was surprised at how much persuasion the pushrod tubes actually needed. It must be atypical because the A/P that built my engine in the first place didn't do it either!

Keep on those wheel pants...they make a huge difference in speed. You'll need every bit of it!